From 13e7ee113bb71c9c996556ab95ed764543e21fa4 Mon Sep 17 00:00:00 2001
From: Elias Sadek <elias.sadek@metoffice.gov.uk>
Date: Mon, 19 Aug 2024 16:05:29 +0100
Subject: [PATCH 01/16] added functional timestamps

---
 lib/iris/mesh/components.py | 169 +++++++++++++++++++++---------------
 1 file changed, 101 insertions(+), 68 deletions(-)

diff --git a/lib/iris/mesh/components.py b/lib/iris/mesh/components.py
index a5936388f8..2e7a39b95c 100644
--- a/lib/iris/mesh/components.py
+++ b/lib/iris/mesh/components.py
@@ -1138,6 +1138,10 @@ def all_connectivities(self):
         """All the :class:`~iris.mesh.Connectivity` instances of the :class:`MeshXY`."""
         return self._connectivity_manager.all_members
 
+    @property
+    def timestamp(self):
+        return MAX(self._coord_manager.timestamp, self._connectivity_manager.timestamp)
+
     @property
     def all_coords(self):
         """All the :class:`~iris.coords.AuxCoord` coordinates of the :class:`MeshXY`."""
@@ -2001,6 +2005,7 @@ def __init__(self, node_x, node_y, edge_x=None, edge_y=None):
         # optional coordinates
         self.edge_x = edge_x
         self.edge_y = edge_y
+        self.timestamp = datetime.now()
 
     def __eq__(self, other):
         # TBD: this is a minimalist implementation and requires to be revisited
@@ -2031,6 +2036,7 @@ def __str__(self):
         return f"{self.__class__.__name__}({', '.join(args)})"
 
     def _remove(self, **kwargs):
+        self.timestamp = datetime.now()
         result = {}
         members = self.filters(**kwargs)
 
@@ -2045,6 +2051,7 @@ def _remove(self, **kwargs):
         return result
 
     def _setter(self, element, axis, coord, shape):
+        self.timestamp = datetime.now()
         axis = axis.lower()
         member = f"{element}_{axis}"
 
@@ -2138,6 +2145,7 @@ def node_y(self, coord):
         self._setter(element="node", axis="y", coord=coord, shape=self._node_shape)
 
     def _add(self, coords):
+        self.timestamp = datetime.now()
         member_x, member_y = coords._fields
 
         # deal with the special case where both members are changing
@@ -2377,6 +2385,7 @@ def __init__(self, *connectivities):
         self.ALL = self.REQUIRED + self.OPTIONAL
         self._members = {member: None for member in self.ALL}
         self.add(*connectivities)
+        self.timestamp = datetime.now()
 
     def __eq__(self, other):
         # TBD: this is a minimalist implementation and requires to be revisited
@@ -2423,6 +2432,7 @@ def add(self, *connectivities):
         # manager.
         # No warning is raised for duplicate cf_roles - user is trusted to
         # validate their outputs.
+        self.timestamp = datetime.now()
         add_dict = {}
         for connectivity in connectivities:
             if not isinstance(connectivity, Connectivity):
@@ -2564,6 +2574,7 @@ def remove(
         contains_edge=None,
         contains_face=None,
     ):
+        self.timestamp = datetime.now()
         removal_dict = self.filters(
             item=item,
             standard_name=standard_name,
@@ -2724,74 +2735,7 @@ def __init__(
             raise ValueError(msg)
         # Held in metadata, readable as self.axis, but cannot set it.
         self._metadata_manager.axis = axis
-
-        points, bounds = self._construct_access_arrays()
-        if points is None:
-            # TODO: we intend to support this in future, but it will require
-            #  extra work to refactor the parent classes.
-            msg = "Cannot yet create a MeshCoord without points."
-            raise ValueError(msg)
-
-        # Get the 'coord identity' metadata from the relevant node-coordinate.
-        node_coord = self.mesh.coord(location="node", axis=self.axis)
-        node_metadict = node_coord.metadata._asdict()
-        # Use node metadata, unless location is face/edge.
-        use_metadict = node_metadict.copy()
-        if location != "node":
-            # Location is either "edge" or "face" - get the relevant coord.
-            location_coord = self.mesh.coord(location=location, axis=axis)
-
-            # Take the MeshCoord metadata from the 'location' coord.
-            use_metadict = location_coord.metadata._asdict()
-            unit_unknown = Unit(None)
-
-            # N.B. at present, coords in a MeshXY are stored+accessed by 'axis', which
-            # means they must have a standard_name.  So ...
-            # (a) the 'location' (face/edge) coord *always* has a usable phenomenon
-            #     identity.
-            # (b) we still want to check that location+node coords have the same
-            #     phenomenon (i.e. physical meaning identity + units), **but** ...
-            # (c) we will accept/ignore some differences : not just "var_name", but
-            #     also "long_name" *and* "attributes".  So it is *only* "standard_name"
-            #     and "units" that cause an error if they differ.
-            for key in ("standard_name", "units"):
-                bounds_value = use_metadict[key]
-                nodes_value = node_metadict[key]
-                if key == "units" and (
-                    bounds_value == unit_unknown or nodes_value == unit_unknown
-                ):
-                    # Allow "any" unit to match no-units (for now)
-                    continue
-                if bounds_value != nodes_value:
-
-                    def fix_repr(val):
-                        # Tidy values appearance by converting Unit to string, and
-                        # wrapping strings in '', but leaving other types as a
-                        # plain str() representation.
-                        if isinstance(val, Unit):
-                            val = str(val)
-                        if isinstance(val, str):
-                            val = repr(val)
-                        return val
-
-                    nodes_value, bounds_value = [
-                        fix_repr(val) for val in (nodes_value, bounds_value)
-                    ]
-                    msg = (
-                        f"Node coordinate {node_coord!r} disagrees with the "
-                        f"{location} coordinate {location_coord!r}, "
-                        f'in having a "{key}" value of {nodes_value} '
-                        f"instead of {bounds_value}."
-                    )
-                    raise ValueError(msg)
-
-        # Don't use 'coord_system' as a constructor arg, since for
-        # MeshCoords it is deduced from the mesh.
-        # (Otherwise a non-None coord_system breaks the 'copy' operation)
-        use_metadict.pop("coord_system")
-
-        # Call parent constructor to handle the common constructor args.
-        super().__init__(points, bounds=bounds, **use_metadict)
+        self._load_points_and_bounds()
 
     # Define accessors for MeshCoord-specific properties mesh/location/axis.
     # These are all read-only.
@@ -2808,6 +2752,31 @@ def location(self):
     def axis(self):
         return self._metadata_manager.axis
 
+    @property
+    def points(self):
+        """The coordinate points values as a NumPy array."""
+        if self.timestamp < self._mesh.timestamp or self.timestamp is None:
+            self._load_points_and_bounds()
+        return self._values
+
+    @points.setter
+    def points(self, value):
+        if value:
+            msg = "Cannot set 'points' on a MeshCoord."
+            raise ValueError(msg)
+
+    @property
+    def bounds(self):
+        if self.timestamp < self._mesh.timestamp or self.timestamp is None:
+            self._load_points_and_bounds()
+        return self.bounds
+
+    @bounds.setter
+    def bounds(self, value):
+        if value:
+            msg = "Cannot set 'bounds' on a MeshCoord."
+            raise ValueError(msg)
+
     # Provide overrides to mimic the Coord-specific properties that are not
     # supported by MeshCoord, i.e. "coord_system" and "climatological".
     # These mimic the Coord properties, but always return fixed 'null' values.
@@ -3017,6 +2986,70 @@ def summary(self, *args, **kwargs):
             result = "\n".join(lines)
         return result
 
+    def _load_points_and_bounds(self):
+        points, bounds = self._construct_access_arrays()
+        if points is None:
+            # TODO: we intend to support this in future, but it will require
+            #  extra work to refactor the parent classes.
+            msg = "Cannot yet create a MeshCoord without points."
+            raise ValueError(msg)
+
+        # Get the 'coord identity' metadata from the relevant node-coordinate.
+        node_coord = self.mesh.coord(include_nodes=True, axis=self.axis)
+        node_metadict = node_coord.metadata._asdict()
+        # Use node metadata, unless location is face/edge.
+        use_metadict = node_metadict.copy()
+        if location != "node":
+            # Location is either "edge" or "face" - get the relevant coord.
+            kwargs = {f"include_{location}s": True, "axis": axis}
+            location_coord = self.mesh.coord(**kwargs)
+
+            # Take the MeshCoord metadata from the 'location' coord.
+            use_metadict = location_coord.metadata._asdict()
+            unit_unknown = Unit(None)
+
+            # N.B. at present, coords in a Mesh are stored+accessed by 'axis', which
+            # means they must have a standard_name.  So ...
+            # (a) the 'location' (face/edge) coord *always* has a usable phenomenon
+            #     identity.
+            # (b) we still want to check that location+node coords have the same
+            #     phenomenon (i.e. physical meaning identity + units), **but** ...
+            # (c) we will accept/ignore some differences : not just "var_name", but
+            #     also "long_name" *and* "attributes".  So it is *only* "standard_name"
+            #     and "units" that cause an error if they differ.
+            for key in ("standard_name", "units"):
+                bounds_value = use_metadict[key]
+                nodes_value = node_metadict[key]
+                if key == "units" and (
+                        bounds_value == unit_unknown or nodes_value == unit_unknown
+                ):
+                    # Allow "any" unit to match no-units (for now)
+                    continue
+                if bounds_value != nodes_value:
+
+                    def fix_repr(val):
+                        # Tidy values appearance by converting Unit to string, and
+                        # wrapping strings in '', but leaving other types as a
+                        # plain str() representation.
+                        if isinstance(val, Unit):
+                            val = str(val)
+                        if isinstance(val, str):
+                            val = repr(val)
+                        return val
+
+                    nodes_value, bounds_value = [
+                        fix_repr(val) for val in (nodes_value, bounds_value)
+                    ]
+                    msg = (
+                        f"Node coordinate {node_coord!r} disagrees with the "
+                        f"{location} coordinate {location_coord!r}, "
+                        f'in having a "{key}" value of {nodes_value} '
+                        f"instead of {bounds_value}."
+                    )
+                    raise ValueError(msg)
+            super().__init__(points, bounds=bounds, **use_metadict)
+            self.timestamp = self._mesh.timestamp
+
     def _construct_access_arrays(self):
         """Build lazy points and bounds arrays.
 

From 7b32abe214330d294b7f540c8774a2fca668781c Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 19 Aug 2024 15:07:00 +0000
Subject: [PATCH 02/16] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 lib/iris/mesh/components.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/iris/mesh/components.py b/lib/iris/mesh/components.py
index 2e7a39b95c..1d9fbb0fc6 100644
--- a/lib/iris/mesh/components.py
+++ b/lib/iris/mesh/components.py
@@ -3021,7 +3021,7 @@ def _load_points_and_bounds(self):
                 bounds_value = use_metadict[key]
                 nodes_value = node_metadict[key]
                 if key == "units" and (
-                        bounds_value == unit_unknown or nodes_value == unit_unknown
+                    bounds_value == unit_unknown or nodes_value == unit_unknown
                 ):
                     # Allow "any" unit to match no-units (for now)
                     continue

From 824c8ae9683344c45b3133fe1b600ef5e4ae116a Mon Sep 17 00:00:00 2001
From: Elias Sadek <elias.sadek@metoffice.gov.uk>
Date: Tue, 20 Aug 2024 02:11:29 +0100
Subject: [PATCH 03/16] wip

---
 lib/iris/mesh/components.py           | 40 +++++++++++++++------------
 lib/iris/tests/unit/cube/test_Cube.py |  4 +++
 2 files changed, 27 insertions(+), 17 deletions(-)

diff --git a/lib/iris/mesh/components.py b/lib/iris/mesh/components.py
index 2e7a39b95c..149d241596 100644
--- a/lib/iris/mesh/components.py
+++ b/lib/iris/mesh/components.py
@@ -30,6 +30,7 @@
 from ..exceptions import ConnectivityNotFoundError, CoordinateNotFoundError
 from ..util import array_equal, clip_string, guess_coord_axis
 from ..warnings import IrisVagueMetadataWarning
+from datetime import datetime
 
 # Configure the logger.
 logger = get_logger(__name__, propagate=True, handler=False)
@@ -1140,7 +1141,8 @@ def all_connectivities(self):
 
     @property
     def timestamp(self):
-        return MAX(self._coord_manager.timestamp, self._connectivity_manager.timestamp)
+        """The most recent time and date that the mesh was edited."""
+        return max(self._coord_manager.timestamp, self._connectivity_manager.timestamp)
 
     @property
     def all_coords(self):
@@ -2005,6 +2007,8 @@ def __init__(self, node_x, node_y, edge_x=None, edge_y=None):
         # optional coordinates
         self.edge_x = edge_x
         self.edge_y = edge_y
+        # makes a note of when the mesh coordinates were last edited, for use in
+        # ensuring MeshCoords are up to date
         self.timestamp = datetime.now()
 
     def __eq__(self, other):
@@ -2385,6 +2389,8 @@ def __init__(self, *connectivities):
         self.ALL = self.REQUIRED + self.OPTIONAL
         self._members = {member: None for member in self.ALL}
         self.add(*connectivities)
+        # makes a note of when the mesh connectivities were last edited, for use in
+        # ensuring MeshCoords are up to date
         self.timestamp = datetime.now()
 
     def __eq__(self, other):
@@ -2735,7 +2741,8 @@ def __init__(
             raise ValueError(msg)
         # Held in metadata, readable as self.axis, but cannot set it.
         self._metadata_manager.axis = axis
-        self._load_points_and_bounds()
+        points, bounds = self._load_points_and_bounds()
+        super().__init__(points, bounds=bounds, **use_metadict)
 
     # Define accessors for MeshCoord-specific properties mesh/location/axis.
     # These are all read-only.
@@ -2755,25 +2762,25 @@ def axis(self):
     @property
     def points(self):
         """The coordinate points values as a NumPy array."""
-        if self.timestamp < self._mesh.timestamp or self.timestamp is None:
-            self._load_points_and_bounds()
-        return self._values
+        if self.timestamp < self.mesh.timestamp or self.timestamp is None:
+            self._values, _, _ = self._load_points_and_bounds()
+        return super._values
 
     @points.setter
     def points(self, value):
-        if value:
+        if len(value) > 0:
             msg = "Cannot set 'points' on a MeshCoord."
             raise ValueError(msg)
 
     @property
     def bounds(self):
         if self.timestamp < self._mesh.timestamp or self.timestamp is None:
-            self._load_points_and_bounds()
-        return self.bounds
+            _, self.bounds, _ = self._load_points_and_bounds()
+        return super.bounds
 
     @bounds.setter
     def bounds(self, value):
-        if value:
+        if len(value) > 0 and self.bounds:
             msg = "Cannot set 'bounds' on a MeshCoord."
             raise ValueError(msg)
 
@@ -2995,20 +3002,19 @@ def _load_points_and_bounds(self):
             raise ValueError(msg)
 
         # Get the 'coord identity' metadata from the relevant node-coordinate.
-        node_coord = self.mesh.coord(include_nodes=True, axis=self.axis)
+        node_coord = self.mesh.coord(location="node", axis=self.axis)
         node_metadict = node_coord.metadata._asdict()
         # Use node metadata, unless location is face/edge.
         use_metadict = node_metadict.copy()
-        if location != "node":
+        if self.location != "node":
             # Location is either "edge" or "face" - get the relevant coord.
-            kwargs = {f"include_{location}s": True, "axis": axis}
-            location_coord = self.mesh.coord(**kwargs)
+            location_coord = self.mesh.coord(location=location, axis=self.axis)
 
             # Take the MeshCoord metadata from the 'location' coord.
             use_metadict = location_coord.metadata._asdict()
             unit_unknown = Unit(None)
 
-            # N.B. at present, coords in a Mesh are stored+accessed by 'axis', which
+            # N.B. at present, coords in a MeshXY are stored+accessed by 'axis', which
             # means they must have a standard_name.  So ...
             # (a) the 'location' (face/edge) coord *always* has a usable phenomenon
             #     identity.
@@ -3042,13 +3048,13 @@ def fix_repr(val):
                     ]
                     msg = (
                         f"Node coordinate {node_coord!r} disagrees with the "
-                        f"{location} coordinate {location_coord!r}, "
+                        f"{self.location} coordinate {location_coord!r}, "
                         f'in having a "{key}" value of {nodes_value} '
                         f"instead of {bounds_value}."
                     )
                     raise ValueError(msg)
-            super().__init__(points, bounds=bounds, **use_metadict)
-            self.timestamp = self._mesh.timestamp
+            self.timestamp = self.mesh.timestamp
+            return points, bounds, use_metadict
 
     def _construct_access_arrays(self):
         """Build lazy points and bounds arrays.
diff --git a/lib/iris/tests/unit/cube/test_Cube.py b/lib/iris/tests/unit/cube/test_Cube.py
index 878a793448..64d8e8f24c 100644
--- a/lib/iris/tests/unit/cube/test_Cube.py
+++ b/lib/iris/tests/unit/cube/test_Cube.py
@@ -2058,6 +2058,10 @@ def test_mesh(self):
         result = self.cube.mesh
         self.assertIs(result, self.mesh)
 
+    def test_mesh_timestamp(self):
+        result = self.cube.mesh.timestamp
+
+
     def test_no_mesh(self):
         # Replace standard setUp cube with a no-mesh version.
         _add_test_meshcube(self, nomesh=True)

From 9abb8e2fa997a3f30c5f682103aaeafb2c429a59 Mon Sep 17 00:00:00 2001
From: Elias Sadek <elias.sadek@metoffice.gov.uk>
Date: Tue, 20 Aug 2024 02:17:52 +0100
Subject: [PATCH 04/16] wip

---
 lib/iris/tests/unit/cube/test_Cube.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/iris/tests/unit/cube/test_Cube.py b/lib/iris/tests/unit/cube/test_Cube.py
index 64d8e8f24c..207fe8555f 100644
--- a/lib/iris/tests/unit/cube/test_Cube.py
+++ b/lib/iris/tests/unit/cube/test_Cube.py
@@ -2060,7 +2060,7 @@ def test_mesh(self):
 
     def test_mesh_timestamp(self):
         result = self.cube.mesh.timestamp
-
+        self.assertNotNone(result)
 
     def test_no_mesh(self):
         # Replace standard setUp cube with a no-mesh version.

From 75a471f74452c9931f69ca56b97850778c3b31b9 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Tue, 20 Aug 2024 01:18:49 +0000
Subject: [PATCH 05/16] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 lib/iris/mesh/components.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/iris/mesh/components.py b/lib/iris/mesh/components.py
index 7d201d02fd..887702d813 100644
--- a/lib/iris/mesh/components.py
+++ b/lib/iris/mesh/components.py
@@ -13,6 +13,7 @@
 from collections import namedtuple
 from collections.abc import Container
 from contextlib import contextmanager
+from datetime import datetime
 from typing import Iterable
 import warnings
 
@@ -30,7 +31,6 @@
 from ..exceptions import ConnectivityNotFoundError, CoordinateNotFoundError
 from ..util import array_equal, clip_string, guess_coord_axis
 from ..warnings import IrisVagueMetadataWarning
-from datetime import datetime
 
 # Configure the logger.
 logger = get_logger(__name__, propagate=True, handler=False)

From 378e6428aa6a3afbdd1eb6cc60451908d74166ec Mon Sep 17 00:00:00 2001
From: Elias Sadek <elias.sadek@metoffice.gov.uk>
Date: Tue, 20 Aug 2024 09:42:14 +0100
Subject: [PATCH 06/16] a couple of small changes

---
 lib/iris/mesh/components.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/lib/iris/mesh/components.py b/lib/iris/mesh/components.py
index 7d201d02fd..8e120ad01a 100644
--- a/lib/iris/mesh/components.py
+++ b/lib/iris/mesh/components.py
@@ -2741,7 +2741,7 @@ def __init__(
             raise ValueError(msg)
         # Held in metadata, readable as self.axis, but cannot set it.
         self._metadata_manager.axis = axis
-        points, bounds = self._load_points_and_bounds()
+        points, bounds, use_metadict = self._load_points_and_bounds()
         super().__init__(points, bounds=bounds, **use_metadict)
 
     # Define accessors for MeshCoord-specific properties mesh/location/axis.
@@ -2763,7 +2763,7 @@ def axis(self):
     def points(self):
         """The coordinate points values as a NumPy array."""
         if self.timestamp < self.mesh.timestamp or self.timestamp is None:
-            self._values, _, _ = self._load_points_and_bounds()
+            self.points, self.bounds, _ = self._load_points_and_bounds()
         return super._values
 
     @points.setter
@@ -2775,7 +2775,7 @@ def points(self, value):
     @property
     def bounds(self):
         if self.timestamp < self._mesh.timestamp or self.timestamp is None:
-            _, self.bounds, _ = self._load_points_and_bounds()
+            self.points, self.bounds, _ = self._load_points_and_bounds()
         return super.bounds
 
     @bounds.setter
@@ -3008,7 +3008,7 @@ def _load_points_and_bounds(self):
         use_metadict = node_metadict.copy()
         if self.location != "node":
             # Location is either "edge" or "face" - get the relevant coord.
-            location_coord = self.mesh.coord(location=location, axis=self.axis)
+            location_coord = self.mesh.coord(location=self.location, axis=self.axis)
 
             # Take the MeshCoord metadata from the 'location' coord.
             use_metadict = location_coord.metadata._asdict()

From 56f994cf399d46359e2c891a5a67da3bc0b34e16 Mon Sep 17 00:00:00 2001
From: Elias Sadek <elias.sadek@metoffice.gov.uk>
Date: Tue, 20 Aug 2024 10:04:42 +0100
Subject: [PATCH 07/16] fixed super calls

---
 lib/iris/mesh/components.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/iris/mesh/components.py b/lib/iris/mesh/components.py
index 614b838a51..2c9fd37407 100644
--- a/lib/iris/mesh/components.py
+++ b/lib/iris/mesh/components.py
@@ -2764,7 +2764,7 @@ def points(self):
         """The coordinate points values as a NumPy array."""
         if self.timestamp < self.mesh.timestamp or self.timestamp is None:
             self.points, self.bounds, _ = self._load_points_and_bounds()
-        return super._values
+        return super().points
 
     @points.setter
     def points(self, value):
@@ -2776,7 +2776,7 @@ def points(self, value):
     def bounds(self):
         if self.timestamp < self._mesh.timestamp or self.timestamp is None:
             self.points, self.bounds, _ = self._load_points_and_bounds()
-        return super.bounds
+        return super().bounds
 
     @bounds.setter
     def bounds(self, value):

From 092e3548b245745bd31e0a0e5331612777e839ac Mon Sep 17 00:00:00 2001
From: Elias Sadek <elias.sadek@metoffice.gov.uk>
Date: Tue, 20 Aug 2024 11:21:00 +0100
Subject: [PATCH 08/16] easy review comments

---
 lib/iris/mesh/components.py | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/lib/iris/mesh/components.py b/lib/iris/mesh/components.py
index 2c9fd37407..ec43b70437 100644
--- a/lib/iris/mesh/components.py
+++ b/lib/iris/mesh/components.py
@@ -1141,7 +1141,8 @@ def all_connectivities(self):
 
     @property
     def timestamp(self):
-        """The most recent time and date that the mesh was edited."""
+        """The most recent time and date that the mesh coordinates and or connecitivities
+        were edited."""
         return max(self._coord_manager.timestamp, self._connectivity_manager.timestamp)
 
     @property
@@ -2742,6 +2743,11 @@ def __init__(
         # Held in metadata, readable as self.axis, but cannot set it.
         self._metadata_manager.axis = axis
         points, bounds, use_metadict = self._load_points_and_bounds()
+        # Don't use 'coord_system' as a constructor arg, since for
+        # MeshCoords it is deduced from the mesh.
+        # (Otherwise a non-None coord_system breaks the 'copy' operation)
+        use_metadict.pop("coord_system")
+
         super().__init__(points, bounds=bounds, **use_metadict)
 
     # Define accessors for MeshCoord-specific properties mesh/location/axis.
@@ -2774,7 +2780,7 @@ def points(self, value):
 
     @property
     def bounds(self):
-        if self.timestamp < self._mesh.timestamp or self.timestamp is None:
+        if self.timestamp < self.mesh.timestamp or self.timestamp is None:
             self.points, self.bounds, _ = self._load_points_and_bounds()
         return super().bounds
 

From 3cbe9c07b6ee386489757b93fe625416dc2d129d Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Tue, 20 Aug 2024 10:21:43 +0000
Subject: [PATCH 09/16] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 lib/iris/mesh/components.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/iris/mesh/components.py b/lib/iris/mesh/components.py
index ec43b70437..3aa7ccab7a 100644
--- a/lib/iris/mesh/components.py
+++ b/lib/iris/mesh/components.py
@@ -1142,7 +1142,8 @@ def all_connectivities(self):
     @property
     def timestamp(self):
         """The most recent time and date that the mesh coordinates and or connecitivities
-        were edited."""
+        were edited.
+        """
         return max(self._coord_manager.timestamp, self._connectivity_manager.timestamp)
 
     @property

From 0fc009937cca24332ab07e2c391615f3729ad79a Mon Sep 17 00:00:00 2001
From: Elias Sadek <elias.sadek@metoffice.gov.uk>
Date: Tue, 20 Aug 2024 15:18:47 +0100
Subject: [PATCH 10/16] Implemented metadata property. Currently fails on
 circular

---
 lib/iris/mesh/components.py | 67 ++++++++++++++++++++++++++++++++-----
 1 file changed, 58 insertions(+), 9 deletions(-)

diff --git a/lib/iris/mesh/components.py b/lib/iris/mesh/components.py
index 3aa7ccab7a..c4d289523c 100644
--- a/lib/iris/mesh/components.py
+++ b/lib/iris/mesh/components.py
@@ -2001,7 +2001,7 @@ class _Mesh1DCoordinateManager:
     def __init__(self, node_x, node_y, edge_x=None, edge_y=None):
         # initialise all the coordinates
         self.ALL = self.REQUIRED + self.OPTIONAL
-        self._members = {member: None for member in self.ALL}
+        self._members_dict = {member: None for member in self.ALL}
 
         # required coordinates
         self.node_x = node_x
@@ -2023,6 +2023,7 @@ def __getstate__(self):
     def __iter__(self):
         for item in self._members.items():
             yield item
+            # ELIASISCOOL
 
     def __ne__(self, other):
         result = self.__eq__(other)
@@ -2106,9 +2107,20 @@ def _edge_shape(self):
     def _node_shape(self):
         return self._shape(element="node")
 
+    @property
+    def _members(self):
+        self.timestamp = datetime.now()
+        return self._members_dict
+
+    @_members.setter
+    def _members(self, value):
+        self.timestamp = datetime.now()
+        self._members_dict = value
+
     @property
     def all_members(self):
         return Mesh1DCoords(**self._members)
+    # ELIASISCOOL
 
     @property
     def edge_coords(self):
@@ -2118,6 +2130,8 @@ def edge_coords(self):
     def edge_x(self):
         return self._members["edge_x"]
 
+    # ELIASISCOOL
+
     @edge_x.setter
     def edge_x(self, coord):
         self._setter(element="edge", axis="x", coord=coord, shape=self._edge_shape)
@@ -2126,6 +2140,8 @@ def edge_x(self, coord):
     def edge_y(self):
         return self._members["edge_y"]
 
+    # ELIASISCOOL
+
     @edge_y.setter
     def edge_y(self, coord):
         self._setter(element="edge", axis="y", coord=coord, shape=self._edge_shape)
@@ -2138,6 +2154,8 @@ def node_coords(self):
     def node_x(self):
         return self._members["node_x"]
 
+    # ELIASISCOOL
+
     @node_x.setter
     def node_x(self, coord):
         self._setter(element="node", axis="x", coord=coord, shape=self._node_shape)
@@ -2389,7 +2407,7 @@ def __init__(self, *connectivities):
                 raise ValueError(message)
 
         self.ALL = self.REQUIRED + self.OPTIONAL
-        self._members = {member: None for member in self.ALL}
+        self._members_dict = {member: None for member in self.ALL}
         self.add(*connectivities)
         # makes a note of when the mesh connectivities were last edited, for use in
         # ensuring MeshCoords are up to date
@@ -2434,6 +2452,16 @@ def __str__(self):
     def all_members(self):
         return NotImplemented
 
+    @property
+    def _members(self):
+        self.timestamp = datetime.now()
+        return self._members_dict
+
+    @_members.setter
+    def _members(self, value):
+        self.timestamp = datetime.now()
+        self._members_dict = value
+
     def add(self, *connectivities):
         # Since Connectivity classes include their cf_role, no setters will be
         # provided, just a means to add one or more connectivities to the
@@ -2711,7 +2739,7 @@ def __init__(
         axis,
     ):
         # Setup the metadata.
-        self._metadata_manager = metadata_manager_factory(MeshCoordMetadata)
+        self._metadata_manager_temp = metadata_manager_factory(MeshCoordMetadata)
 
         # Validate and record the class-specific constructor args.
         if not isinstance(mesh, MeshXY):
@@ -2743,7 +2771,8 @@ def __init__(
             raise ValueError(msg)
         # Held in metadata, readable as self.axis, but cannot set it.
         self._metadata_manager.axis = axis
-        points, bounds, use_metadict = self._load_points_and_bounds()
+        points, bounds = self._load_points_and_bounds()
+        use_metadict = self._load_metadata()
         # Don't use 'coord_system' as a constructor arg, since for
         # MeshCoords it is deduced from the mesh.
         # (Otherwise a non-None coord_system breaks the 'copy' operation)
@@ -2770,7 +2799,9 @@ def axis(self):
     def points(self):
         """The coordinate points values as a NumPy array."""
         if self.timestamp < self.mesh.timestamp or self.timestamp is None:
-            self.points, self.bounds, _ = self._load_points_and_bounds()
+            points, bounds = self._load_points_and_bounds()
+            super(MeshCoord, self.__class__).points.fset(self, points)
+            super(MeshCoord, self.__class__).bounds.fset(self, bounds)
         return super().points
 
     @points.setter
@@ -2782,7 +2813,9 @@ def points(self, value):
     @property
     def bounds(self):
         if self.timestamp < self.mesh.timestamp or self.timestamp is None:
-            self.points, self.bounds, _ = self._load_points_and_bounds()
+            points, bounds = self._load_points_and_bounds()
+            super(MeshCoord, self.__class__).points.fset(self, points)
+            super(MeshCoord, self.__class__).bounds.fset(self, bounds)
         return super().bounds
 
     @bounds.setter
@@ -2790,6 +2823,20 @@ def bounds(self, value):
         if len(value) > 0 and self.bounds:
             msg = "Cannot set 'bounds' on a MeshCoord."
             raise ValueError(msg)
+        else:
+            super(MeshCoord, self.__class__).bounds.fset(self, value)
+
+    @property
+    def _metadata_manager(self):
+        # An explanatory comment.
+        use_metadict = self._load_metadata()
+        self._metadata_manager_temp.standard_name = something
+        # Etcetera for all standard coord metadata
+        # THIS INCLUDES DETERMINING THE CORRECT VALUE, AS IN
+        #  THE CURRENT BLOCK WITHIN _load_points_and_bounds
+
+        return self._metadata_manager_temp
+
 
     # Provide overrides to mimic the Coord-specific properties that are not
     # supported by MeshCoord, i.e. "coord_system" and "climatological".
@@ -3007,7 +3054,10 @@ def _load_points_and_bounds(self):
             #  extra work to refactor the parent classes.
             msg = "Cannot yet create a MeshCoord without points."
             raise ValueError(msg)
+            self.timestamp = self.mesh.timestamp
+            return points, bounds
 
+    def _load_metadata(self):
         # Get the 'coord identity' metadata from the relevant node-coordinate.
         node_coord = self.mesh.coord(location="node", axis=self.axis)
         node_metadict = node_coord.metadata._asdict()
@@ -3034,7 +3084,7 @@ def _load_points_and_bounds(self):
                 bounds_value = use_metadict[key]
                 nodes_value = node_metadict[key]
                 if key == "units" and (
-                    bounds_value == unit_unknown or nodes_value == unit_unknown
+                        bounds_value == unit_unknown or nodes_value == unit_unknown
                 ):
                     # Allow "any" unit to match no-units (for now)
                     continue
@@ -3060,8 +3110,7 @@ def fix_repr(val):
                         f"instead of {bounds_value}."
                     )
                     raise ValueError(msg)
-            self.timestamp = self.mesh.timestamp
-            return points, bounds, use_metadict
+            return use_metadict
 
     def _construct_access_arrays(self):
         """Build lazy points and bounds arrays.

From 67c9ed0017c9ff8f0bd8009d413f20d25b1b5345 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Tue, 20 Aug 2024 14:21:29 +0000
Subject: [PATCH 11/16] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 lib/iris/mesh/components.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/iris/mesh/components.py b/lib/iris/mesh/components.py
index c4d289523c..8c9984d59f 100644
--- a/lib/iris/mesh/components.py
+++ b/lib/iris/mesh/components.py
@@ -2120,6 +2120,7 @@ def _members(self, value):
     @property
     def all_members(self):
         return Mesh1DCoords(**self._members)
+
     # ELIASISCOOL
 
     @property
@@ -2837,7 +2838,6 @@ def _metadata_manager(self):
 
         return self._metadata_manager_temp
 
-
     # Provide overrides to mimic the Coord-specific properties that are not
     # supported by MeshCoord, i.e. "coord_system" and "climatological".
     # These mimic the Coord properties, but always return fixed 'null' values.
@@ -3084,7 +3084,7 @@ def _load_metadata(self):
                 bounds_value = use_metadict[key]
                 nodes_value = node_metadict[key]
                 if key == "units" and (
-                        bounds_value == unit_unknown or nodes_value == unit_unknown
+                    bounds_value == unit_unknown or nodes_value == unit_unknown
                 ):
                     # Allow "any" unit to match no-units (for now)
                     continue

From d8ad4dd5f4cdf25871e56e45e7f7ecbbf8decf68 Mon Sep 17 00:00:00 2001
From: Elias Sadek <elias.sadek@metoffice.gov.uk>
Date: Thu, 22 Aug 2024 15:24:23 +0100
Subject: [PATCH 12/16] bounds are circular looping

---
 lib/iris/mesh/components.py | 34 +++++++++++++++++++---------------
 1 file changed, 19 insertions(+), 15 deletions(-)

diff --git a/lib/iris/mesh/components.py b/lib/iris/mesh/components.py
index c4d289523c..f64edefcbf 100644
--- a/lib/iris/mesh/components.py
+++ b/lib/iris/mesh/components.py
@@ -2760,7 +2760,7 @@ def __init__(
             )
             raise ValueError(msg)
         # Held in metadata, readable as self.location, but cannot set it.
-        self._metadata_manager.location = location
+        self._metadata_manager_temp.location = location
 
         if axis not in MeshXY.AXES:
             # The valid axes are defined by the MeshXY class.
@@ -2770,7 +2770,7 @@ def __init__(
             )
             raise ValueError(msg)
         # Held in metadata, readable as self.axis, but cannot set it.
-        self._metadata_manager.axis = axis
+        self._metadata_manager_temp.axis = axis
         points, bounds = self._load_points_and_bounds()
         use_metadict = self._load_metadata()
         # Don't use 'coord_system' as a constructor arg, since for
@@ -2806,7 +2806,7 @@ def points(self):
 
     @points.setter
     def points(self, value):
-        if len(value) > 0:
+        if len(value) != 0 or not(value is None):
             msg = "Cannot set 'points' on a MeshCoord."
             raise ValueError(msg)
 
@@ -2820,7 +2820,7 @@ def bounds(self):
 
     @bounds.setter
     def bounds(self, value):
-        if len(value) > 0 and self.bounds:
+        if len(value) != 0 or not(value is None) and self.bounds:
             msg = "Cannot set 'bounds' on a MeshCoord."
             raise ValueError(msg)
         else:
@@ -2830,11 +2830,13 @@ def bounds(self, value):
     def _metadata_manager(self):
         # An explanatory comment.
         use_metadict = self._load_metadata()
-        self._metadata_manager_temp.standard_name = something
-        # Etcetera for all standard coord metadata
-        # THIS INCLUDES DETERMINING THE CORRECT VALUE, AS IN
-        #  THE CURRENT BLOCK WITHIN _load_points_and_bounds
-
+        self._metadata_manager_temp.standard_name = use_metadict["standard_name"]
+        self._metadata_manager_temp.long_name = use_metadict["long_name"]
+        self._metadata_manager_temp.var_name = use_metadict["var_name"]
+        self._metadata_manager_temp.units = use_metadict["units"]
+        self._metadata_manager_temp.attributes = use_metadict["attributes"]
+        self._metadata_manager_temp.coord_system = use_metadict["coord_system"]
+        self._metadata_manager_temp.climatological = use_metadict["climatological"]
         return self._metadata_manager_temp
 
 
@@ -3054,18 +3056,20 @@ def _load_points_and_bounds(self):
             #  extra work to refactor the parent classes.
             msg = "Cannot yet create a MeshCoord without points."
             raise ValueError(msg)
-            self.timestamp = self.mesh.timestamp
-            return points, bounds
+        self.timestamp = self.mesh.timestamp
+        return points, bounds
 
     def _load_metadata(self):
+        axis = self._metadata_manager_temp.axis
+        location = self._metadata_manager_temp.location
         # Get the 'coord identity' metadata from the relevant node-coordinate.
-        node_coord = self.mesh.coord(location="node", axis=self.axis)
+        node_coord = self.mesh.coord(location="node", axis=axis)
         node_metadict = node_coord.metadata._asdict()
         # Use node metadata, unless location is face/edge.
         use_metadict = node_metadict.copy()
-        if self.location != "node":
+        if location != "node":
             # Location is either "edge" or "face" - get the relevant coord.
-            location_coord = self.mesh.coord(location=self.location, axis=self.axis)
+            location_coord = self.mesh.coord(location=location, axis=axis)
 
             # Take the MeshCoord metadata from the 'location' coord.
             use_metadict = location_coord.metadata._asdict()
@@ -3105,7 +3109,7 @@ def fix_repr(val):
                     ]
                     msg = (
                         f"Node coordinate {node_coord!r} disagrees with the "
-                        f"{self.location} coordinate {location_coord!r}, "
+                        f"{location} coordinate {location_coord!r}, "
                         f'in having a "{key}" value of {nodes_value} '
                         f"instead of {bounds_value}."
                     )

From 050d47bb2f9bad74fd6319e4cc8bfe3fbe81ad85 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Thu, 22 Aug 2024 14:25:39 +0000
Subject: [PATCH 13/16] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 lib/iris/mesh/components.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/iris/mesh/components.py b/lib/iris/mesh/components.py
index 4dda67b3e7..24fd00689d 100644
--- a/lib/iris/mesh/components.py
+++ b/lib/iris/mesh/components.py
@@ -2807,7 +2807,7 @@ def points(self):
 
     @points.setter
     def points(self, value):
-        if len(value) != 0 or not(value is None):
+        if len(value) != 0 or not (value is None):
             msg = "Cannot set 'points' on a MeshCoord."
             raise ValueError(msg)
 
@@ -2821,7 +2821,7 @@ def bounds(self):
 
     @bounds.setter
     def bounds(self, value):
-        if len(value) != 0 or not(value is None) and self.bounds:
+        if len(value) != 0 or not (value is None) and self.bounds:
             msg = "Cannot set 'bounds' on a MeshCoord."
             raise ValueError(msg)
         else:

From 9c0b61da28ed87e17abb69c98a0f181fdb27017c Mon Sep 17 00:00:00 2001
From: Elias Sadek <elias.sadek@metoffice.gov.uk>
Date: Thu, 3 Oct 2024 16:44:16 +0100
Subject: [PATCH 14/16] fixed bounds issue

---
 lib/iris/mesh/components.py           | 36 +++++++++++++++++++--------
 lib/iris/tests/unit/cube/test_Cube.py |  2 +-
 2 files changed, 27 insertions(+), 11 deletions(-)

diff --git a/lib/iris/mesh/components.py b/lib/iris/mesh/components.py
index 4dda67b3e7..7ad5585d59 100644
--- a/lib/iris/mesh/components.py
+++ b/lib/iris/mesh/components.py
@@ -2739,6 +2739,7 @@ def __init__(
         location,
         axis,
     ):
+        self._read_only_points_and_bounds = True
         # Setup the metadata.
         self._metadata_manager_temp = metadata_manager_factory(MeshCoordMetadata)
 
@@ -2778,8 +2779,8 @@ def __init__(
         # MeshCoords it is deduced from the mesh.
         # (Otherwise a non-None coord_system breaks the 'copy' operation)
         use_metadict.pop("coord_system")
-
-        super().__init__(points, bounds=bounds, **use_metadict)
+        with self._writable_points_and_bounds():
+            super().__init__(points, bounds=bounds, **use_metadict)
 
     # Define accessors for MeshCoord-specific properties mesh/location/axis.
     # These are all read-only.
@@ -2796,6 +2797,19 @@ def location(self):
     def axis(self):
         return self._metadata_manager.axis
 
+    @contextmanager
+    def _writable_points_and_bounds(self):
+        """
+        Context manager to allow bounds and points to be set during __init__.
+        `points` currently doesn't encounter any issues without this manager, but
+        is included here for future proofing.
+        """
+        try:
+            self._read_only_points_and_bounds = False
+            yield
+        finally:
+            self._read_only_points_and_bounds = True
+
     @property
     def points(self):
         """The coordinate points values as a NumPy array."""
@@ -2807,9 +2821,10 @@ def points(self):
 
     @points.setter
     def points(self, value):
-        if len(value) != 0 or not(value is None):
-            msg = "Cannot set 'points' on a MeshCoord."
-            raise ValueError(msg)
+        if self._read_only_points_and_bounds:
+            if len(value) != 0 or not(value is None):
+                msg = "Cannot set 'points' on a MeshCoord."
+                raise ValueError(msg)
 
     @property
     def bounds(self):
@@ -2821,11 +2836,12 @@ def bounds(self):
 
     @bounds.setter
     def bounds(self, value):
-        if len(value) != 0 or not(value is None) and self.bounds:
-            msg = "Cannot set 'bounds' on a MeshCoord."
-            raise ValueError(msg)
-        else:
-            super(MeshCoord, self.__class__).bounds.fset(self, value)
+        if self._read_only_points_and_bounds:
+            if len(value) != 0: #or not(value is None) and self.bounds:
+                msg = "Cannot set 'bounds' on a MeshCoord."
+                raise ValueError(msg)
+            else:
+                super(MeshCoord, self.__class__).bounds.fset(self, value)
 
     @property
     def _metadata_manager(self):
diff --git a/lib/iris/tests/unit/cube/test_Cube.py b/lib/iris/tests/unit/cube/test_Cube.py
index 207fe8555f..37736e82d7 100644
--- a/lib/iris/tests/unit/cube/test_Cube.py
+++ b/lib/iris/tests/unit/cube/test_Cube.py
@@ -2060,7 +2060,7 @@ def test_mesh(self):
 
     def test_mesh_timestamp(self):
         result = self.cube.mesh.timestamp
-        self.assertNotNone(result)
+        self.assertIsNotNone(result)
 
     def test_no_mesh(self):
         # Replace standard setUp cube with a no-mesh version.

From 99c995ad7fb4d4a870ea1f19443674bd6dc89305 Mon Sep 17 00:00:00 2001
From: Elias Sadek <elias.sadek@metoffice.gov.uk>
Date: Thu, 3 Oct 2024 16:53:57 +0100
Subject: [PATCH 15/16] merge conflicts

---
 lib/iris/mesh/components.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/iris/mesh/components.py b/lib/iris/mesh/components.py
index 7ad5585d59..a3c2d7b941 100644
--- a/lib/iris/mesh/components.py
+++ b/lib/iris/mesh/components.py
@@ -14,7 +14,7 @@
 from collections.abc import Container
 from contextlib import contextmanager
 from datetime import datetime
-from typing import Iterable
+from typing import Iterable, Literal
 import warnings
 
 from cf_units import Unit

From adbb97b339662a4f70c3e3618afa747827e3cee6 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Thu, 3 Oct 2024 15:57:27 +0000
Subject: [PATCH 16/16] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 lib/iris/mesh/components.py | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/lib/iris/mesh/components.py b/lib/iris/mesh/components.py
index 9440bdb833..702bcbe510 100644
--- a/lib/iris/mesh/components.py
+++ b/lib/iris/mesh/components.py
@@ -2802,8 +2802,7 @@ def axis(self):
 
     @contextmanager
     def _writable_points_and_bounds(self):
-        """
-        Context manager to allow bounds and points to be set during __init__.
+        """Context manager to allow bounds and points to be set during __init__.
         `points` currently doesn't encounter any issues without this manager, but
         is included here for future proofing.
         """
@@ -2825,7 +2824,7 @@ def points(self):
     @points.setter
     def points(self, value):
         if self._read_only_points_and_bounds:
-            if len(value) != 0 or not(value is None):
+            if len(value) != 0 or not (value is None):
                 msg = "Cannot set 'points' on a MeshCoord."
                 raise ValueError(msg)
 
@@ -2840,7 +2839,7 @@ def bounds(self):
     @bounds.setter
     def bounds(self, value):
         if self._read_only_points_and_bounds:
-            if len(value) != 0: #or not(value is None) and self.bounds:
+            if len(value) != 0:  # or not(value is None) and self.bounds:
                 msg = "Cannot set 'bounds' on a MeshCoord."
                 raise ValueError(msg)
             else: