Replaceing the metadata parser from packaging.metadata by LalatenduMohanty · Pull Request #607 · python-wheel-build/fromager

LalatenduMohanty · 2025-05-16T06:01:32Z

Replaces the Python email library parser with packaging.metadata.Metadata for parsing wheel/package metadata.

Fixes #561

LalatenduMohanty · 2025-07-05T03:20:19Z

dhellmann

This looks good to me. How many places in the code do we do something similar to parse metadata? How useful would it be to have a function that takes a path and returns the metadata?

tiran · 2025-07-07T04:44:21Z

packaging.metadata.parse_email does not round trip and looses any field that it does not understand. Is this okay? Do we need a round trip-safe function?

LalatenduMohanty · 2025-07-07T13:47:53Z

How many places in the code do we do something similar to parse metadata? How useful would it be to have a function that takes a path and returns the metadata?

My bad. I should have checked all code to see if same pattern exists else where. I can see https://github.com/python-wheel-build/fromager/blob/main/src/fromager/candidate.py#L82 . I do not think we need a common function yet. PTAL and let me know.

LalatenduMohanty · 2025-07-07T13:56:04Z

packaging.metadata.parse_email does not round trip and looses any field that it does not understand. Is this okay? Do we need a round trip-safe function?

Let me get back to you on this.

LalatenduMohanty · 2025-07-07T19:59:04Z

@tiran Since fromager only reads metadata for dependency resolution and doesn't need to write it back, round trip safety isn't necessary. The benefits of type safety and validation from packaging.metadata outweigh the loss of unknown fields that aren't being used anyway.

rd4398

Looks good to me! I will wait for @tiran to approve since he had clarification questions

src/fromager/candidate.py

tiran · 2025-07-17T04:09:06Z

src/fromager/bootstrapper.py

+            raw_metadata, _ = parse_email(f.read())
+            metadata = Metadata.from_raw(raw_metadata)


Why are you using parse_email() + Metadata.from_raw() instead of Metadata.parse_email()? The Metadata.parse_email() combines parse_email(), Metadata.from_raw(), and additional validation.

This code should probably use fromager.dependencies.parse_metadata(metadata_filename).

src/fromager/candidate.py

src/fromager/dependencies.py

LalatenduMohanty · 2025-12-04T22:12:37Z

@tiran PTAL when you have a chance

src/fromager/dependencies.py

tests/test_dependencies.py

tiran · 2026-01-27T08:12:29Z

src/fromager/dependencies.py

+    wheel_name_parts = wheel_filename.stem.split("-")
+    dist_name = wheel_name_parts[0]
+    dist_version = wheel_name_parts[1]
+    predicted_dist_info = f"{dist_name}-{dist_version}.dist-info/METADATA"


Let's not invent our own wheel parsing algorithm. The function add_extra_metadata_to_wheels has some code to get the dist-info directory of a wheel file. Perhaps move the code into a common, shared helper?

Good catch. I am going to use parse_wheel_filename() i.e. the same underlying function from add_extra_metadata_to_wheels

tiran · 2026-01-27T08:12:36Z

src/fromager/bootstrapper.py

-            p = BytesParser()
-            metadata = p.parse(f, headersonly=True)
-        return Version(metadata["Version"])
+        metadata = dependencies.parse_metadata(metadata_filename)


parse_metadata validates the metadata by default. This will raise an exception if the metadata version does not match the metadata content, e.g. license-file field in Metadata < 2.4.

We should add validate=False here i.e. metadata = dependencies.parse_metadata(metadata_filename, validate=False)

src/fromager/dependencies.py

Replaces the Python email library parser with packaging.metadata.Metadata for parsing wheel/package metadata. Fixes: python-wheel-build#561 Co-Authored-By: Claude <claude@anthropic.com> Signed-off-by: Lalatendu Mohanty <lmohanty@redhat.com>

dhellmann

I'm happy with this version. @tiran had more detailed comments, so I will leave it open for him to approve.

LalatenduMohanty mentioned this pull request May 16, 2025

use packaging library to parse metadata instead of doing it ourselves #561

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LalatenduMohanty changed the title ~~[WIP] Replaceing the metadata parser from packaging.metadata~~ Replaceing the metadata parser from packaging.metadata Jul 4, 2025

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		raw_metadata, _ = parse_email(f.read())
		metadata = Metadata.from_raw(raw_metadata)

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LalatenduMohanty commented May 16, 2025 •

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