ci: derive ToolchainFeatureSupport from conanfile.py via AST

Instead of duplicating the compiler version thresholds in
generate-job-matrix.py (e.g. std_format=version >= 13 for GCC),
parse _feature_compatibility directly from conanfile.py using the
ast module. This makes conanfile.py the single source of truth for
compiler feature support, and the CI matrix generator stays in sync
automatically whenever conanfile.py is updated.

Author: mpusz

.github/generate-job-matrix.py

@@ -1,20 +1,58 @@
 import argparse
+import ast
 import json
 import os
+import pathlib
 import random
 import typing
 from types import SimpleNamespace
 
+from job_matrix import ToolchainFeatureSupport  # used by _make_feature_support
 from job_matrix import (
     CombinationCollector,
     Compiler,
     ConanOptions,
     Configuration,
     Toolchain,
-    ToolchainFeatureSupport,
 )
 
 
+def _load_feature_compat() -> dict:
+    """Parse _feature_compatibility from conanfile.py via AST (no Conan import needed)."""
+    conanfile = pathlib.Path(__file__).parent.parent / "conanfile.py"
+    tree = ast.parse(conanfile.read_text())
+    for node in ast.walk(tree):
+        if (
+            isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef))
+            and node.name == "_feature_compatibility"
+        ):
+            for stmt in node.body:
+                if isinstance(stmt, ast.Return):
+                    return ast.literal_eval(stmt.value)
+    raise RuntimeError("Could not find _feature_compatibility in conanfile.py")
+
+
+_FEATURE_COMPAT = _load_feature_compat()
+
+
+def _make_feature_support(
+    conan_compiler: str, version: int, *, freestanding: bool = False
+) -> ToolchainFeatureSupport:
+    """Derive ToolchainFeatureSupport from conanfile.py's _feature_compatibility."""
+
+    def supports(feature: str) -> bool:
+        min_ver = _FEATURE_COMPAT[feature]["compiler"].get(conan_compiler)
+        return bool(min_ver and version >= int(min_ver))
+
+    return ToolchainFeatureSupport(
+        cxx_modules=supports("cxx_modules"),
+        std_format=supports("std_format"),
+        import_std=supports("import_std"),
+        explicit_this=supports("explicit_this"),
+        freestanding=freestanding,
+    )
+
+
 def make_gcc_config(version: int) -> Toolchain:
     return Toolchain(
         name=f"GCC-{version}",
@@ -25,11 +63,7 @@ def make_gcc_config(version: int) -> Toolchain:
             cc=f"gcc-{version}",
             cxx=f"g++-{version}",
         ),
-        feature_support=ToolchainFeatureSupport(
-            std_format=version >= 13,
-            explicit_this=version >= 14,
-            freestanding=True,
-        ),
+        feature_support=_make_feature_support("gcc", version, freestanding=True),
     )
 
 
@@ -43,13 +77,7 @@ def make_clang_config(
             version=version,
         ),
         lib="libc++",
-        feature_support=ToolchainFeatureSupport(
-            cxx_modules=version >= 17,
-            std_format=version >= 17,
-            import_std=version >= 18,
-            explicit_this=version >= 18,
-            freestanding=True,
-        ),
+        feature_support=_make_feature_support("clang", version, freestanding=True),
     )
     match architecture:
         case "x86-64":
@@ -79,10 +107,7 @@ def make_apple_clang_config(os: str, version: str) -> Toolchain:
             cc="clang",
             cxx="clang++",
         ),
-        feature_support=ToolchainFeatureSupport(
-            std_format=major_version >= 16,
-            explicit_this=major_version >= 17,
-        ),
+        feature_support=_make_feature_support("apple-clang", major_version),
     )
     return ret
 
@@ -97,10 +122,7 @@ def make_msvc_config(release: str, version: int) -> Toolchain:
             cc="",
             cxx="",
         ),
-        feature_support=ToolchainFeatureSupport(
-            std_format=version >= 194,
-            explicit_this=version >= 194,
-        ),
+        feature_support=_make_feature_support("msvc", version),
     )
     return ret