marker/extras: port pypa conformance tables + uv-pep508 carets (rstudio/package-manager#19392)

NOTICE

@@ -173,3 +173,42 @@ pgregory.net/rapid is licensed under the Mozilla Public License, Version 2.0.
 It is a test-only dependency: internal/proptest contains only _test.go files,
 so rapid does not appear in this module's non-test import graph and is not
 built into any consumer that imports this library.
+
+The marker/ package's conformance tests port the marker evaluation and parse
+cases of pypa/packaging (https://github.com/pypa/packaging), Copyright (c)
+Donald Stufft and individual contributors, specifically tests/test_markers.py's
+classes TestOperatorEvaluation and TestMarker and its module-level and/or
+evaluation tests, pinned at commit 4eb0753dba8fcaaac8eb75463374e448f0931558
+(identical at release 26.3), licensed under the Apache License, Version 2.0.
+Translated from Python/pytest to Go table-driven tests, in
+marker/conformance_test.go. Upstream tests resting on implementation details
+with no counterpart here are not ported, and the reason is recorded in the
+file's header: TestNode, TestDefaultEnvironment (the live interpreter),
+__str__/__repr__/__hash__/__eq__, the operator-overload tests, every
+test_pickle_*, evaluate(context=...), and the set-valued "extras"/
+"dependency_groups" marker variables (PEP 685/735), which this package's
+grammar does not recognize at all. Where a Go expectation differs from
+upstream's literal assertion the divergence is annotated inline at its table.
+
+The extras/ package's conformance tests port the name-canonicalization cases
+of pypa/packaging (https://github.com/pypa/packaging), Copyright (c) Donald
+Stufft and individual contributors, specifically tests/test_utils.py's
+test_canonicalize_name and the non-validating half of
+test_canonicalize_name_invalid, pinned at commit
+4eb0753dba8fcaaac8eb75463374e448f0931558, licensed under the Apache License,
+Version 2.0. Translated from Python/pytest to Go table-driven tests, in
+extras/conformance_test.go.
+
+The internal/pep508 package's error-position conformance tests port input
+strings and caret span offsets - not message text - from Astral uv's
+uv-pep508 crate (https://github.com/astral-sh/uv), specifically
+crates/uv-pep508/src/lib.rs's `mod tests` error_* cases, pinned at commit
+01cb90c1a4f88af09906cb60de9766d2add4a062 (release 0.12.18). uv-pep508
+overrides uv's workspace license to Apache-2.0 OR BSD-2-Clause (Copyright (c)
+2023 konstin) and ships its own license files; this material is taken under
+the Apache-2.0 arm. Translated from Rust/insta snapshots to Go table-driven
+tests, in internal/pep508/error_position_test.go, asserting this package's own
+byte offsets and message text throughout - never uv's prose, and never any
+case behind uv's "non-pep508-extensions" cargo feature (unnamed
+direct-reference requirements, which this module's grammar has no
+counterpart for).

extras/conformance_test.go

@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+//
+// Portions of this file port test cases from pypa/packaging
+// (https://github.com/pypa/packaging), specifically tests/test_utils.py's
+// test_canonicalize_name, used under the Apache License, Version 2.0
+// (dual-licensed Apache-2.0 OR BSD-2-Clause; see NOTICE for full license and
+// copyright detail).
+// Changed: translated from Python/pytest to Go table-driven tests; see the
+// divergence notes below for cases where the Go expectation intentionally
+// differs from upstream's literal assertion.
+//
+// Of test_utils.py's 11 test functions, only this one maps cleanly onto this
+// module: 6 are parse_wheel_filename/parse_sdist_filename (wheelname/'s
+// concern, and parse_sdist_filename has no Go counterpart at all), and
+// test_canonicalize_version, test_is_normalized_name, and the validating half
+// of canonicalize_name(validate=True) have no Go implementation anywhere in
+// this module. Only extras.Normalize (canonicalize_name) is ported here.
+//
+// Upstream pinned at 4eb0753dba8fcaaac8eb75463374e448f0931558 (identical at
+// release 26.3: the only test_markers.py/test_utils.py change since is a type
+// annotation, not a case).
+
+package extras
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// Ported from pypa/packaging tests/test_utils.py, test_canonicalize_name.
+// Pinned: 4eb0753dba8fcaaac8eb75463374e448f0931558 (L23-L39 at that commit).
+// https://github.com/pypa/packaging/blob/4eb0753dba8fcaaac8eb75463374e448f0931558/tests/test_utils.py#L23-L39
+func TestConformance_CanonicalizeName(t *testing.T) {
+	tests := []struct {
+		name string
+		want string
+	}{
+		{"foo", "foo"},
+		{"Foo", "foo"},
+		{"fOo", "foo"},
+		{"foo.bar", "foo-bar"},
+		{"Foo.Bar", "foo-bar"},
+		{"Foo.....Bar", "foo-bar"},
+		{"foo_bar", "foo-bar"},
+		{"foo___bar", "foo-bar"},
+		{"foo-bar", "foo-bar"},
+		{"foo----bar", "foo-bar"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.want, Normalize(tt.name))
+		})
+	}
+}
+
+// Ported from pypa/packaging tests/test_utils.py,
+// test_canonicalize_name_invalid - the NON-VALIDATING half only
+// (`assert canonicalize_name(name) == expected`). The validating half
+// (`canonicalize_name(name, validate=True)` raising InvalidName) has no
+// counterpart: Normalize has no validate mode, and PEP 503/685 name-validity
+// checking is not implemented anywhere in this module. A half-port, not a
+// skip: the assertion this function still makes is real and ported as-is.
+// Pinned: 4eb0753dba8fcaaac8eb75463374e448f0931558 (L42-L57 at that commit).
+// https://github.com/pypa/packaging/blob/4eb0753dba8fcaaac8eb75463374e448f0931558/tests/test_utils.py#L42-L57
+func TestConformance_CanonicalizeNameInvalid_NonValidatingHalf(t *testing.T) {
+	tests := []struct {
+		name string
+		want string
+	}{
+		{"_not_legal", "-not-legal"},
+		{"hi\n", "hi\n"},
+		{"\nhi", "\nhi"},
+		{"h\ni", "h\ni"},
+		{"hi\r", "hi\r"},
+		{"\rhi", "\rhi"},
+		{"h\ri", "h\ri"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.want, Normalize(tt.name))
+		})
+	}
+}