cli: Remove hand-rolled WHEEL parsing/mutation code

The PyPA Binary Distribution Format spec says the WHEEL metadata file is
"in the same basic key: value format" as the METADATA file.  METADATA in
turn is governed by the Core Metadata Specifications, which say: "In the
absence of a precise definition, the practical standard is set by what the
standard library email.parser module can parse using the compat32 policy."

wheel.bdist_wheel accordingly uses email.generator.BytesGenerator to
generate WHEEL, but the CLI `pack` and `tags` commands opt to
hand-implement WHEEL parsing and mutation.  Their mutation functions,
set_tags() and set_build_number(), append any new headers to the existing
WHEEL file.  Since WHEEL tends to have a trailing blank line (separating
the headers from the nonexistent body), the new headers end up in the
"body" and are ignored by any tool that parses WHEEL with email.parser.

In addition, both functions assume that WHEEL uses CRLF line endings,
while bdist_wheel (and email.generator with the compat32 policy)
specifically always writes LF line endings.  This turns out okay for
set_tags(), which rewrites the whole file, but set_build_number() ends up
appending a CRLF-terminated line to a file with LF-terminated lines.

Fix all this by removing the hand-written parsing/mutation functions in
favor of email.parser and email.generator.

docs/news.rst

@@ -3,6 +3,10 @@ Release Notes
 
 **UNRELEASED**
 
+- Fixed ``wheel pack`` and ``wheel tags`` writing updated ``WHEEL`` fields after a
+  blank line, causing other tools to ignore them
+- Fixed ``wheel pack`` and ``wheel tags`` writing ``WHEEL`` with CRLF line endings or
+  a mix of CRLF and LF
 - Allow removing build tag with ``wheel tags --build ""``
 - Fixed ``wheel pack --build-number ""`` not removing build tag from ``WHEEL``
   (above changes by Benjamin Gilbert)

src/wheel/cli/pack.py

@@ -1,13 +1,15 @@
 from __future__ import annotations
 
+import email.policy
 import os.path
 import re
+from email.generator import BytesGenerator
+from email.parser import BytesParser
 
 from wheel.cli import WheelError
 from wheel.wheelfile import WheelFile
 
 DIST_INFO_RE = re.compile(r"^(?P<namever>(?P<name>.+?)-(?P<ver>\d.*?))\.dist-info$")
-BUILD_NUM_RE = re.compile(rb"Build: (\d\w*)\r?\n")
 
 
 def pack(directory: str, dest_dir: str, build_number: str | None) -> None:
@@ -35,10 +37,11 @@ def pack(directory: str, dest_dir: str, build_number: str | None) -> None:
     name_version = DIST_INFO_RE.match(dist_info_dir).group("namever")
 
     # Read the tags and the existing build number from .dist-info/WHEEL
-    existing_build_number = None
     wheel_file_path = os.path.join(directory, dist_info_dir, "WHEEL")
     with open(wheel_file_path, "rb") as f:
-        tags, existing_build_number = read_tags(f.read())
+        info = BytesParser(policy=email.policy.compat32).parse(f)
+        tags: list[str] = info.get_all("Tag", [])
+        existing_build_number = info.get("Build")
 
         if not tags:
             raise WheelError(
@@ -49,17 +52,14 @@ def pack(directory: str, dest_dir: str, build_number: str | None) -> None:
     # Set the wheel file name and add/replace/remove the Build tag in .dist-info/WHEEL
     build_number = build_number if build_number is not None else existing_build_number
     if build_number is not None:
+        del info["Build"]
         if build_number:
+            info["Build"] = build_number
             name_version += "-" + build_number
 
         if build_number != existing_build_number:
-            with open(wheel_file_path, "rb+") as f:
-                wheel_file_content = f.read()
-                wheel_file_content = set_build_number(wheel_file_content, build_number)
-
-                f.seek(0)
-                f.truncate()
-                f.write(wheel_file_content)
+            with open(wheel_file_path, "wb") as f:
+                BytesGenerator(f, maxheaderlen=0).flatten(info)
 
     # Reassemble the tags for the wheel file
     tagline = compute_tagline(tags)
@@ -73,45 +73,6 @@ def pack(directory: str, dest_dir: str, build_number: str | None) -> None:
     print("OK")
 
 
-def read_tags(input_str: bytes) -> tuple[list[str], str | None]:
-    """Read tags from a string.
-
-    :param input_str: A string containing one or more tags, separated by spaces
-    :return: A list of tags and a list of build tags
-    """
-
-    tags = []
-    existing_build_number = None
-    for line in input_str.splitlines():
-        if line.startswith(b"Tag: "):
-            tags.append(line.split(b" ")[1].rstrip().decode("ascii"))
-        elif line.startswith(b"Build: "):
-            existing_build_number = line.split(b" ")[1].rstrip().decode("ascii")
-
-    return tags, existing_build_number
-
-
-def set_build_number(wheel_file_content: bytes, build_number: str | None) -> bytes:
-    """Compute a build tag and add/replace/remove as necessary.
-
-    :param wheel_file_content: The contents of .dist-info/WHEEL
-    :param build_number: The build tags present in .dist-info/WHEEL
-    :return: The (modified) contents of .dist-info/WHEEL
-    """
-    replacement = (
-        ("Build: %s\r\n" % build_number).encode("ascii") if build_number else b""
-    )
-
-    wheel_file_content, num_replaced = BUILD_NUM_RE.subn(
-        replacement, wheel_file_content
-    )
-
-    if not num_replaced:
-        wheel_file_content += replacement
-
-    return wheel_file_content
-
-
 def compute_tagline(tags: list[str]) -> str:
     """Compute a tagline from a list of tags.
 

src/wheel/cli/tags.py

@@ -1,11 +1,12 @@
 from __future__ import annotations
 
+import email.policy
 import itertools
 import os
 from collections.abc import Iterable
+from email.parser import BytesParser
 
 from ..wheelfile import WheelFile
-from .pack import read_tags, set_build_number
 
 
 def _compute_tags(original_tags: Iterable[str], new_tags: str | None) -> set[str]:
@@ -48,6 +49,7 @@ def tags(
         assert f.filename, f"{f.filename} must be available"
 
         wheel_info = f.read(f.dist_info_path + "/WHEEL")
+        info = BytesParser(policy=email.policy.compat32).parsebytes(wheel_info)
 
         original_wheel_name = os.path.basename(f.filename)
         namever = f.parsed_filename.group("namever")
@@ -56,7 +58,8 @@ def tags(
         original_abi_tags = f.parsed_filename.group("abi").split(".")
         original_plat_tags = f.parsed_filename.group("plat").split(".")
 
-    tags, existing_build_tag = read_tags(wheel_info)
+    tags: list[str] = info.get_all("Tag", [])
+    existing_build_tag = info.get("Build")
 
     impls = {tag.split("-")[0] for tag in tags}
     abivers = {tag.split("-")[1] for tag in tags}
@@ -103,12 +106,13 @@ def tags(
     final_wheel_name = "-".join(final_tags) + ".whl"
 
     if original_wheel_name != final_wheel_name:
-        tags = [
-            f"{a}-{b}-{c}"
-            for a, b, c in itertools.product(
-                final_python_tags, final_abi_tags, final_plat_tags
-            )
-        ]
+        del info["Tag"], info["Build"]
+        for a, b, c in itertools.product(
+            final_python_tags, final_abi_tags, final_plat_tags
+        ):
+            info["Tag"] = f"{a}-{b}-{c}"
+        if build:
+            info["Build"] = build
 
         original_wheel_path = os.path.join(
             os.path.dirname(f.filename), original_wheel_name
@@ -125,29 +129,11 @@ def tags(
                 if item.filename == f.dist_info_path + "/RECORD":
                     continue
                 if item.filename == f.dist_info_path + "/WHEEL":
-                    content = fin.read(item)
-                    content = set_tags(content, tags)
-                    content = set_build_number(content, build)
-                    fout.writestr(item, content)
+                    fout.writestr(item, info.as_bytes())
                 else:
                     fout.writestr(item, fin.read(item))
 
         if remove:
             os.remove(original_wheel_path)
 
     return final_wheel_name
-
-
-def set_tags(in_string: bytes, tags: Iterable[str]) -> bytes:
-    """Set the tags in the .dist-info/WHEEL file contents.
-
-    :param in_string: The string to modify.
-    :param tags: The tags to set.
-    """
-
-    lines = [line for line in in_string.splitlines() if not line.startswith(b"Tag:")]
-    for tag in tags:
-        lines.append(b"Tag: " + tag.encode("ascii"))
-    in_string = b"\r\n".join(lines) + b"\r\n"
-
-    return in_string

tests/cli/test_tags.py

@@ -39,8 +39,8 @@ def test_python_tags(wheelpath):
     with WheelFile(str(output_file)) as f:
         output = f.read(f.dist_info_path + "/WHEEL")
     assert (
-        output == b"Wheel-Version: 1.0\r\nGenerator: bdist_wheel (0.30.0)"
-        b"\r\nRoot-Is-Purelib: false\r\nTag: py3-none-any\r\n"
+        output == b"Wheel-Version: 1.0\nGenerator: bdist_wheel (0.30.0)"
+        b"\nRoot-Is-Purelib: false\nTag: py3-none-any\n\n"
     )
     output_file.unlink()
 
@@ -153,9 +153,9 @@ def test_multi_tags(wheelpath):
         output = f.read(f.dist_info_path + "/WHEEL")
     assert (
         output
-        == b"Wheel-Version: 1.0\r\nGenerator: bdist_wheel (0.30.0)\r\nRoot-Is-Purelib:"
-        b" false\r\nTag: py2-none-linux_x86_64\r\nTag: py3-none-linux_x86_64\r\nTag:"
-        b" py4-none-linux_x86_64\r\nBuild: 1\r\n"
+        == b"Wheel-Version: 1.0\nGenerator: bdist_wheel (0.30.0)\nRoot-Is-Purelib:"
+        b" false\nTag: py2-none-linux_x86_64\nTag: py3-none-linux_x86_64\nTag:"
+        b" py4-none-linux_x86_64\nBuild: 1\n\n"
     )
     output_file.unlink()