Several fixes to WHEEL metadata handling (#588)

* cli: Add missing return type annotations

* bdist_wheel: Remove dead code for postprocessing WHEEL line endings

The default policies of Message and BytesGenerator always produce LF
line endings, so there's never a CRLF to match.  If there were, the
existing code would have incorrectly replaced CRLF with CR, and then
test_wheelfile_line_endings() would have failed.

* cli: Fix removing build tag with `wheel pack --build-number ""`

There's an existing test for this case, which verifies that the original
build tag is removed from the wheel filename and is *not* removed from
the WHEEL metadata.  Presumably this is not what was intended.

BUILD_NUM_RE assumed that it would only match at end of file, but there's
at least a newline in the way.  Fix it, and the test.

* cli: Allow removing build tag with `wheel tags --build ""`

For symmetry with `wheel pack`.  The functionality works already; we just
need to fix the command-line validation.

* test: Restructure test_pack() around email.message.Message

We're about to change pack() to emit WHEEL metadata with LF-terminated
lines and a trailing blank line.  In some test_pack() parameterizations
we expect to see the original WHEEL file from the test fixture, and in
some, a modified one.  Handle the difference by comparing WHEEL contents
parsed with email.parser, instead of byte strings.

* 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

@@ -1,6 +1,16 @@
 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)
+
 **0.41.3 (2023-10-30)**
 
 - Updated vendored ``packaging`` to 23.2

src/wheel/bdist_wheel.py

@@ -17,7 +17,6 @@
 from email.generator import BytesGenerator, Generator
 from email.policy import EmailPolicy
 from glob import iglob
-from io import BytesIO
 from shutil import rmtree
 from zipfile import ZIP_DEFLATED, ZIP_STORED
 
@@ -468,10 +467,8 @@ def write_wheelfile(
 
         wheelfile_path = os.path.join(wheelfile_base, "WHEEL")
         log.info(f"creating {wheelfile_path}")
-        buffer = BytesIO()
-        BytesGenerator(buffer, maxheaderlen=0).flatten(msg)
         with open(wheelfile_path, "wb") as f:
-            f.write(buffer.getvalue().replace(b"\r\n", b"\r"))
+            BytesGenerator(f, maxheaderlen=0).flatten(msg)
 
     def _ensure_relative(self, path):
         # copied from dir_util, deleted

src/wheel/cli/__init__.py

@@ -58,7 +58,7 @@ def version_f(args):
 
 
 def parse_build_tag(build_tag: str) -> str:
-    if not build_tag[0].isdigit():
+    if build_tag and not build_tag[0].isdigit():
         raise ArgumentTypeError("build tag must begin with a digit")
     elif "-" in build_tag:
         raise ArgumentTypeError("invalid character ('-') in build tag")

src/wheel/cli/convert.py

@@ -42,7 +42,7 @@ def get_tag(self):
             return bdist_wheel.get_tag(self)
 
 
-def egg2wheel(egg_path: str, dest_dir: str):
+def egg2wheel(egg_path: str, dest_dir: str) -> None:
     filename = os.path.basename(egg_path)
     match = egg_info_re.match(filename)
     if not match:

src/wheel/cli/pack.py

@@ -1,16 +1,18 @@
 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$")
-BUILD_NUM_RE = re.compile(rb"Build: (\d\w*)$")
 
 
-def pack(directory: str, dest_dir: str, build_number: str | None):
+def pack(directory: str, dest_dir: str, build_number: str | None) -> None:
     """Repack a previously unpacked wheel directory into a new wheel file.
 
     The .dist-info/WHEEL file must contain one or more tags so that the target
@@ -35,10 +37,11 @@ def pack(directory: str, dest_dir: str, build_number: str | 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):
     # 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):
     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_pack.py

@@ -1,7 +1,9 @@
 from __future__ import annotations
 
+import email.policy
 import os
-from textwrap import dedent
+from email.message import Message
+from email.parser import BytesParser
 from zipfile import ZipFile
 
 import pytest
@@ -55,22 +57,25 @@ def test_pack(tmp_path_factory, tmp_path, build_tag_arg, existing_build_tag, fil
             if line and not line.startswith(b"test-1.0.dist-info/WHEEL,")
         )
 
-        new_wheel_file_content = zf.read("test-1.0.dist-info/WHEEL")
+        parser = BytesParser(policy=email.policy.compat32)
+        new_wheel_file_content = parser.parsebytes(zf.read("test-1.0.dist-info/WHEEL"))
 
     assert new_record_lines == old_record_lines
 
-    expected_build_num = build_tag_arg or existing_build_tag
-    expected_wheel_content = dedent(
-        """\
-        Wheel-Version: 1.0
-        Generator: bdist_wheel (0.30.0)
-        Root-Is-Purelib: false
-        Tag: py2-none-any
-        Tag: py3-none-any
-    """.replace("\n", "\r\n")
+    # Line endings and trailing blank line will depend on whether WHEEL
+    # was modified.  Circumvent this by comparing parsed key/value pairs.
+    expected_wheel_content = Message()
+    expected_wheel_content["Wheel-Version"] = "1.0"
+    expected_wheel_content["Generator"] = "bdist_wheel (0.30.0)"
+    expected_wheel_content["Root-Is-Purelib"] = "false"
+    expected_wheel_content["Tag"] = "py2-none-any"
+    expected_wheel_content["Tag"] = "py3-none-any"
+    expected_build_num = (
+        build_tag_arg if build_tag_arg is not None else existing_build_tag
     )
     if expected_build_num:
-        expected_wheel_content += "Build: %s\r\n" % expected_build_num
+        expected_wheel_content["Build"] = expected_build_num
 
-    expected_wheel_content = expected_wheel_content.encode("ascii")
-    assert new_wheel_file_content == expected_wheel_content
+    assert sorted(new_wheel_file_content.items()) == sorted(
+        expected_wheel_content.items()
+    )

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()
 
@@ -116,6 +116,8 @@ def test_build_tag(wheelpath):
     assert TESTWHEEL_NAME.replace("-py2", "-1bah-py2") == newname
     output_file = wheelpath.parent / newname
     assert output_file.exists()
+    newname = tags(str(wheelpath), build_tag="")
+    assert TESTWHEEL_NAME == newname
     output_file.unlink()
 
 
@@ -151,9 +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()