Federation Support - Description of custom directives breaks make_federated_schema

[j-riebe]

I stumpled into a problem with the federation support while using custom directives.
It appears that make_federated_schema doesn't support custom directives if they have a description.

The culprit is following function:

ariadne/ariadne/contrib/federation/utils.py

Lines 54 to 61 in ceee00c

	def purge_schema_directives(joined_type_defs: str) -> str:
	"""Remove custom schema directives from federation."""
	joined_type_defs = _r_directive_definition.sub("", joined_type_defs)
	joined_type_defs = _r_directive.sub(
	lambda m: m.group(1) if m.group(2) in _allowed_directives else "",
	joined_type_defs,
	)
	return joined_type_defs

It purges the directives from the schema but keeps the description in place.
This may lead to a violation of the GraphQL Syntax depending on which type definition come next.

The solution would be to extend the regex used to capture the directive definition so that it includes block-strings and single-line-strings.

ariadne/ariadne/contrib/federation/utils.py

Lines 17 to 32 in ceee00c

	_i_token_delimiter = r"(?:^|[\s\r\n]+|$)"
	_i_token_name = "[_A-Za-z][_0-9A-Za-z]*"
	_i_token_arguments = r"\([^)]*\)"
	_i_token_location = "[_A-Za-z][_0-9A-Za-z]*"
	_r_directive_definition = re.compile(
	"("
	f"{_i_token_delimiter}directive"
	f"(?:{_i_token_delimiter})?@({_i_token_name})"
	f"(?:(?:{_i_token_delimiter})?{_i_token_arguments})?"
	f"{_i_token_delimiter}on"
	f"{_i_token_delimiter}(?:[|]{_i_token_delimiter})?{_i_token_location}"
	f"(?:{_i_token_delimiter}[|]{_i_token_delimiter}{_i_token_location})*"
	")"
	f"(?={_i_token_delimiter})",
	)

[j-riebe]

Thx @rafalp

[vikramsubramanian]

It feels like this Regex change would make parsing comments take forever (exponential?)

[j-riebe]

What do you mean by would and it feels?

Are you experiencing "forever"? 😄

[vikramsubramanian]

Hey, sorry for the vagueness.
Every """...""" comment block seems to exponentially grow the time it takes to parse a Graphql block. Simply removing all my comments compiled my code instantly whereas with ~10 comments, the script took >30 mins and ~30s with 1 comment block

[j-riebe]

I'd suggest to open a new issue, that targets the performance issue (as this issue is closed).

Some closing thoughts:
Keep in mind that the original problem is rooted in the use of purge_schema_directives which is reused in make_federated_schema

ariadne/ariadne/contrib/federation/utils.py

Lines 58 to 65 in f37df14

	def purge_schema_directives(joined_type_defs: str) -> str:
	"""Remove custom schema directives from federation."""
	joined_type_defs = _r_directive_definition.sub("", joined_type_defs)
	joined_type_defs = _r_directive.sub(
	lambda m: m.group(1) if m.group(2) in _allowed_directives else "",
	joined_type_defs,
	)
	return joined_type_defs

ariadne/ariadne/contrib/federation/schema.py

Lines 64 to 68 in f37df14

	# Remove custom schema directives (to avoid apollo-gateway crashes).
	# NOTE: This does NOT interfere with ariadne's directives support.
	sdl = purge_schema_directives(type_defs)
	type_token = "extend type" if has_query_type(sdl) else "type"
	federation_service_type = federation_service_type_defs.format(type_token=type_token)

Maybe the true solution lies in removing purge_schema_directives entirely, as its only usage comes with a hacky comment:

(to avoid apollo-gateway crashes)

If one finds another way to avoid apollo-gateway crashes, we don't need that regex.

That being said, #736 also mentions this specific function. Maybe you can find some help there.