Add conformance tests for the 'match_args' parameter to dataclass.

The spec lists 'match_args' as a dataclass parameter that static
type checkers must honor, so it would be good to have tests for it.

Author: rchen152

conformance/results/mypy/dataclasses_match_args.toml

@@ -0,0 +1,7 @@
+conformant = "Pass"
+conformance_automated = "Pass"
+errors_diff = """
+"""
+output = """
+dataclasses_match_args.py:42: error: "type[DC4]" has no attribute "__match_args__"  [attr-defined]
+"""

conformance/results/mypy/version.toml

@@ -1,2 +1,2 @@
 version = "mypy 1.17.0"
-test_duration = 2.7
+test_duration = 2.8

conformance/results/pyre/dataclasses_match_args.toml

@@ -0,0 +1,12 @@
+conformant = "Partial"
+notes = """
+Adds kw-only fields to __match_args__.
+"""
+conformance_automated = "Fail"
+errors_diff = """
+Line 18: Unexpected errors ["dataclasses_match_args.py:18:0 Assert type [70]: Expected `Tuple[typing_extensions.Literal['x']]` but got `Tuple[typing_extensions.Literal['x'], typing_extensions.Literal['*'], typing_extensions.Literal['y']]`."]
+"""
+output = """
+dataclasses_match_args.py:18:0 Assert type [70]: Expected `Tuple[typing_extensions.Literal['x']]` but got `Tuple[typing_extensions.Literal['x'], typing_extensions.Literal['*'], typing_extensions.Literal['y']]`.
+dataclasses_match_args.py:42:0 Undefined attribute [16]: `DC4` has no attribute `__match_args__`.
+"""

conformance/results/pyright/dataclasses_match_args.toml

@@ -0,0 +1,10 @@
+conformant = "Partial"
+notes = """
+Generates __match_args__ when match_args=False.
+"""
+conformance_automated = "Fail"
+errors_diff = """
+Line 42: Expected 1 errors
+"""
+output = """
+"""

conformance/results/pyright/version.toml

@@ -1,2 +1,2 @@
 version = "pyright 1.1.403"
-test_duration = 5.6
+test_duration = 5.7

conformance/results/results.html

@@ -159,10 +159,10 @@ <h3>Python Type System Conformance Test Results</h3>
         <div class="table_container"><table><tbody>
 <tr><th class="col1">&nbsp;</th>
 <th class='tc-header'><div class='tc-name'>mypy 1.17.0</div>
-<div class='tc-time'>2.7sec</div>
+<div class='tc-time'>2.8sec</div>
 </th>
 <th class='tc-header'><div class='tc-name'>pyright 1.1.403</div>
-<div class='tc-time'>5.6sec</div>
+<div class='tc-time'>5.7sec</div>
 </th>
 <th class='tc-header'><div class='tc-name'>pyre 0.9.25</div>
 <div class='tc-time'>3.9sec</div>
@@ -652,6 +652,11 @@ <h3>Python Type System Conformance Test Results</h3>
 <th class="column col2 conformant">Pass</th>
 <th class="column col2 partially-conformant"><div class="hover-text">Partial<span class="tooltip-text" id="bottom"><p>Rejects legitimate use of dataclass field with `kw_only=True`.</p></span></div></th>
 </tr>
+<tr><th class="column col1">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;dataclasses_match_args</th>
+<th class="column col2 conformant">Pass</th>
+<th class="column col2 partially-conformant"><div class="hover-text">Partial<span class="tooltip-text" id="bottom"><p>Generates __match_args__ when match_args=False.</p></span></div></th>
+<th class="column col2 partially-conformant"><div class="hover-text">Partial<span class="tooltip-text" id="bottom"><p>Adds kw-only fields to __match_args__.</p></span></div></th>
+</tr>
 <tr><th class="column col1">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;dataclasses_order</th>
 <th class="column col2 conformant">Pass</th>
 <th class="column col2 conformant">Pass</th>

conformance/tests/dataclasses_match_args.py

@@ -0,0 +1,49 @@
+"""
+Tests the match_args feature of dataclass added in Python 3.10.
+"""
+
+# Specification: https://docs.python.org/3/library/dataclasses.html#module-contents
+
+from dataclasses import dataclass, KW_ONLY
+from typing import assert_type, Literal
+
+# If true, the __match_args__ tuple will be created from the list of non keyword-only parameters to the generated __init__() method
+
+@dataclass(match_args=True)
+class DC1:
+    x: int
+    _: KW_ONLY
+    y: str
+
+assert_type(DC1.__match_args__, tuple[Literal['x']])
+
+# The match_args default is True
+
+@dataclass
+class DC2:
+    x: int
+
+assert_type(DC2.__match_args__, tuple[Literal['x']])
+
+# __match_args__ is created even if __init__() is not generated
+
+@dataclass(match_args=True, init=False)
+class DC3:
+    x: int = 0
+
+assert_type(DC3.__match_args__, tuple[Literal['x']])
+
+# If false, or if __match_args__ is already defined in the class, then __match_args__ will not be generated.
+
+@dataclass(match_args=False)
+class DC4:
+    x: int
+
+DC4.__match_args__  # E
+
+@dataclass(match_args=True)
+class DC5:
+    __match_args__ = ()
+    x: int
+
+assert_type(DC5.__match_args__, tuple[()])