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xacro:loop macro #291

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xacro:loop macro #291

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0f05f1a
Generic loop examples
rhaschke Oct 2, 2021
b15de6a
Allow default arguments for block arguments
rhaschke Sep 9, 2021
26c55ea
Try late evaluation of inserted blocks
rhaschke Sep 9, 2021
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20 changes: 20 additions & 0 deletions examples/loop.xacro
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Original file line number Diff line number Diff line change
@@ -0,0 +1,20 @@
<?xml version="1.0"?>
<macro_library xmlns:xacro="http://www.ros.org/wiki/xacro">
<xacro:macro name="loop" params="items **body:=^">
<xacro:if value="${items}">
<!-- pop first item from list -->
<xacro:property name="item" value="${items[0]}"/>
<xacro:insert_block name="body" />
<!-- recursively call myself -->
<xacro:loop items="${items[1:]}"/>
</xacro:if>
</xacro:macro>

<xacro:property name="items" value="${python.range(5)}" />

<xacro:loop items="${items}">
<body>
<item>item: ${item}</item>
</body>
</xacro:loop>
</macro_library>
61 changes: 34 additions & 27 deletions src/xacro/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -589,6 +589,8 @@ def parse_macro_arg(s):
param, forward, default, rest = m.groups()
if not default:
default = None
elif param[0] == '*':
raise XacroException("Invalid default '{}' for block argument '{}'".format(default, param), macro=m)
return param, (param if forward else None, default), rest
else:
# there is no default specified at all
Expand Down Expand Up @@ -658,8 +660,8 @@ def grab_property(elt, table):
return

if value is None:
name = '**' + name
value = elt # debug
name = '*' + name
value = first_child_element(elt)

replace_node(elt, by=None)

Expand Down Expand Up @@ -799,34 +801,33 @@ def handle_macro_call(node, macros, symbols):
scoped_symbols._setitem(name, eval_text(value, symbols), unevaluated=False)
node.setAttribute(name, "") # suppress second evaluation in eval_all()

# Evaluate block parameters in node
eval_all(node, macros, symbols)

# Fetch block parameters, in order
# Fetch block parameters (in order) or/and defaults for remaining arguments
block = first_child_element(node)
for param in params[:]:
if param[0] == '*':
if not block:
# get potential default
name, default = m.defaultmap.get(param, (None, None))
have_default = name is not None or default is not None

if param[0] == '*': # block argument expected
if block:
params.remove(param)
scoped_symbols[param] = block
block = next_sibling_element(block)
elif have_default:
default = eval_default_arg(name, default, symbols, m)
assert(isinstance(default, xml.dom.minidom.Element))
scoped_symbols._setitem(param, default, unevaluated=False)
params.remove(param)
else:
raise XacroException("Not enough blocks", macro=m)
elif have_default: # a default was specified
default = eval_default_arg(name, default, symbols, m)
scoped_symbols._setitem(param, default, unevaluated=False)
params.remove(param)
scoped_symbols[param] = block
block = next_sibling_element(block)

if block is not None:
raise XacroException("Unused block \"%s\"" % block.tagName, macro=m)

# Try to load defaults for any remaining non-block parameters
for param in params[:]:
# block parameters are not supported for defaults
if param[0] == '*':
continue

# get default
name, default = m.defaultmap.get(param, (None, None))
if name is not None or default is not None:
scoped_symbols._setitem(param, eval_default_arg(name, default, symbols, m), unevaluated=False)
params.remove(param)

if params:
raise XacroException("Undefined parameters [%s]" % ",".join(params), macro=m)

Expand Down Expand Up @@ -894,6 +895,14 @@ def remove_previous_comments(node):
return


def wrap_node(node):
impl = xml.dom.minidom.getDOMImplementation()
doc = impl.createDocument(None, "wrapper", None)
root = doc.documentElement
root.appendChild(node.cloneNode(deep=True))
return root


def eval_all(node, macros, symbols):
"""Recursively evaluate node, expanding macros, replacing properties, and evaluating expressions"""
# evaluate the attributes
Expand Down Expand Up @@ -928,11 +937,9 @@ def eval_all(node, macros, symbols):
else:
raise XacroException("Undefined block \"%s\"" % name)

# cloning block allows to insert the same block multiple times
block = block.cloneNode(deep=True)
# recursively evaluate block
eval_all(block, macros, symbols)
replace_node(node, by=block, content_only=content_only)
wrapper = wrap_node(block) # wrap block into a dummy node
eval_all(wrapper, macros, symbols) # to allow evaluation of the block itself
replace_node(node, by=first_child_element(wrapper), content_only=content_only)

elif node.tagName == 'xacro:include':
process_include(node, macros, symbols, eval_all)
Expand Down