build: override setuptools build backend

- Add custom build backend which overrides certain hooks
- Include custom build backend in sdists via `MANIFEST.in`
- Remove `build>=1.0.0` workaround from `build-and-sign.sh`
- Add build backend tests, update order of tests and coverage config

.codecov.yml

@@ -32,6 +32,7 @@ coverage:
       streamlink:
         threshold: 1
         paths:
+          - "build_backend/"
           - "src/streamlink/"
           - "!src/streamlink/plugins/"
       streamlink_cli:

MANIFEST.in

@@ -5,6 +5,7 @@ include LICENSE*
 include *requirements.txt
 include icon.svg
 
+recursive-include build_backend *
 recursive-include completions *
 recursive-include docs *
 recursive-include tests *

build_backend/__init__.py

@@ -0,0 +1,79 @@
+import shlex
+from typing import List, Optional, Tuple
+
+from setuptools import build_meta as _build_meta
+
+# re-export everything from `setuptools.build_meta`, so that we don't have to worry about any hooks which we don't override
+# https://peps.python.org/pep-0517/
+# https://peps.python.org/pep-0660/
+# noinspection PyUnresolvedReferences
+from setuptools.build_meta import *  # noqa: F403
+from setuptools.command.egg_info import egg_info as _egg_info
+
+
+# ----
+
+
+def get_requires_for_build_wheel(  # type: ignore[no-redef]
+    config_settings: Optional[dict] = None,
+) -> List[str]:  # pragma: no cover
+    # Streamlink publishes three wheels on PyPI: the generic "any" wheel, the "win32" wheel and the "win-amd64" wheel:
+    # The Windows-wheels are special, because they include a "gui_scripts" entry point, which is used by the `pip` frontend
+    # to generate the "streamlinkw" launcher, which doesn't open a terminal window when launching it from a GUI application.
+    #
+    # In order to build these special Windows-wheels, the `--plat-name=...` CLI argument needs to get passed
+    # to the `bdist_wheel` setuptools command (provided by the `wheel` package). With the introduction of PEP517 however,
+    # setuptools's CLI is not used directly anymore, and instead, we have to build the wheels using the `build` package
+    # and the `--wheel --config-setting=--build-option=...` args, which are then forwarded to setuptools via the PEP517 hooks.
+    #
+    # Since `build==1.0.0` though, the `--config-setting` data now gets passed to all build-backend hooks involved,
+    # even `get_requires_for_build_wheel()`. This results in the build failing, as it executes setuptools's `egg_info` command,
+    # which doesn't accept the `--plat-name` argument or any other `bdist_wheel` command options.
+    #
+    # As a consequence of this, we need to override the build-backend and the `get_requires_for_build_wheel()` hook, so that
+    # we can filter out arguments which are not relevant to the `egg_info` command.
+    _filter_cmd_option_args(config_settings, "--build-option", _egg_info.user_options)
+
+    return _build_meta.get_requires_for_build_wheel(config_settings)
+
+
+# ----
+
+
+def _filter_cmd_option_args(
+    config_settings: Optional[dict],
+    key: str,
+    options: List[Tuple[str, Optional[str], str]],
+) -> None:
+    """Filter out args which are not recognized by a specific command and its options"""
+
+    if not config_settings or not config_settings.get(key):
+        return
+
+    parsed = shlex.split(config_settings[key])
+
+    result = []
+    val_next = False
+    for item in parsed:
+        if val_next:
+            val_next = False
+            result.append(item)
+            continue
+        for full, shorthand, *_ in options:
+            is_boolean = full[-1] != "="
+            is_shorthand = shorthand is not None and item == f"-{shorthand}"
+            if not is_boolean and (is_shorthand or item == f"--{full[:-1]}"):
+                val_next = True
+                result.append(item)
+                break
+            if (
+                is_boolean and (is_shorthand or item == f"--{full}")
+                or not is_boolean and item.startswith(f"--{full}")
+            ):
+                result.append(item)
+                break
+
+    if result:
+        config_settings[key] = shlex.join(result)
+    else:
+        del config_settings[key]

build_backend/test_build_backend.py

@@ -0,0 +1,41 @@
+import pytest
+from setuptools.command.egg_info import egg_info
+
+from build_backend import _filter_cmd_option_args
+
+
+@pytest.mark.parametrize(("config_settings", "expected", "options"), [
+    pytest.param(
+        None,
+        None,
+        egg_info.user_options,
+        id="Empty config_settings",
+    ),
+    pytest.param(
+        {"foo": "bar"},
+        {"foo": "bar"},
+        egg_info.user_options,
+        id="No --build-option key",
+    ),
+    pytest.param(
+        {"--build-option": "--egg-base=foo/bar -e baz/qux --tag-build foo -b bar --tag-date --no-date -D"},
+        {"--build-option": "--egg-base=foo/bar -e baz/qux --tag-build foo -b bar --tag-date --no-date -D"},
+        egg_info.user_options,
+        id="All egg_info options",
+    ),
+    pytest.param(
+        {"--build-option": "--foo --bar --baz"},
+        {},
+        egg_info.user_options,
+        id="Options unknown to egg_info",
+    ),
+    pytest.param(
+        {"--build-option": "-p win32 --plat-name win32 --plat-name=win32"},
+        {},
+        egg_info.user_options,
+        id="bdist_wheel --plat-name option",
+    ),
+])
+def test_filter_cmd_option_args(config_settings: dict, expected: str, options: list):
+    _filter_cmd_option_args(config_settings, "--build-option", options)
+    assert config_settings == expected

dev-requirements.txt

@@ -22,6 +22,7 @@ lxml-stubs
 trio-typing
 types-freezegun
 types-requests
+types-setuptools
 types-urllib3
 
 # scripts

pyproject.toml

@@ -1,10 +1,13 @@
 [build-system]
-build-backend = "setuptools.build_meta"
 requires = [
   "setuptools >=64",
   "wheel",
   "versioningit >=2.0.0, <3",
 ]
+# setuptools build-backend override
+# https://setuptools.pypa.io/en/stable/build_meta.html
+backend-path = ["build_backend"]
+build-backend = "__init__"
 
 
 # https://peps.python.org/pep-0621/
@@ -110,6 +113,10 @@ build-file = "streamlink/_version.py"
 # https://docs.pytest.org/en/latest/reference/customize.html#configuration
 # https://docs.pytest.org/en/latest/reference/reference.html#ini-options-ref
 [tool.pytest.ini_options]
+testpaths = [
+  "build_backend",
+  "tests",
+]
 filterwarnings = [
   "always",
   "ignore:::pkg_resources",
@@ -121,6 +128,7 @@ filterwarnings = [
 [tool.coverage.run]
 branch = true
 source = [
+  "build_backend",
   "src",
   "tests",
 ]
@@ -142,7 +150,11 @@ exclude_lines = [
 
 # https://beta.ruff.rs/docs/configuration/
 [tool.ruff]
-src = ["src", "tests"]
+src = [
+  "build_backend",
+  "src",
+  "tests",
+]
 target-version = "py38"
 fix = false
 ignore-init-module-imports = true
@@ -233,6 +245,7 @@ show_error_context = true
 show_column_numbers = true
 warn_no_return = false
 files = [
+  "build_backend",
   "src/streamlink/",
   "src/streamlink_cli/",
   "tests/",

script/build-and-sign.sh

@@ -54,11 +54,10 @@ build() {
     log "Building Streamlink sdist and generic wheel"
     python -m build --outdir "${DIST}" --sdist --wheel
 
-    # TODO: switch from `--build-option` (transitional/"escape hatch") to a custom setuptools build-backend override
-    # Adding `bdist_wheel` in front of `--plat-name=...` is required since `build>=1.0.0` as a workaround
+    # see custom build-system override in pyproject.toml
     for platform in "${WHEEL_PLATFORMS[@]}"; do
         log "Building Streamlink platform-specific wheel for ${platform}"
-        python -m build --outdir "${DIST}" --wheel --config-setting="--build-option=bdist_wheel --plat-name=${platform}"
+        python -m build --outdir "${DIST}" --wheel --config-setting="--build-option=--plat-name=${platform}"
     done
 }
 

tests/conftest.py

@@ -15,6 +15,7 @@
 }
 
 _TEST_PRIORITIES = (
+    "build_backend/",
     "tests/testutils/",
     "tests/utils/",
     None,