fix: state and check the 3.12 build floor

README.md

@@ -131,7 +131,7 @@ python scripts/verify.py --emulator flycast
 python scripts/verify.py --platform retroarch --verbose  # emulator ground truth
 ```
 
-Only dependency: Python 3 + `pyyaml`.
+Requires Python 3.12 and `pyyaml`. The one-line installer alone runs on Python 3.8.
 
 ## Documentation site
 

scripts/generate_readme.py

@@ -581,7 +581,7 @@ def generate_readme(db: dict, platforms_dir: str) -> str:
             "python scripts/verify.py --platform retroarch --verbose  # emulator ground truth",
             "```",
             "",
-            "Only dependency: Python 3 + `pyyaml`.",
+            "Requires Python 3.12 and `pyyaml`. The one-line installer alone runs on Python 3.8.",
             "",
             "## Documentation site",
             "",

scripts/pipeline.py

@@ -33,6 +33,12 @@ import sys
 import time
 from pathlib import Path
 
+# The build scripts use syntax CPython 3.12 introduced (generate_readme's
+# f-strings, generate_pack's parenthesized context managers). On an older
+# interpreter the run got through the packs and failed hours in, at step 7.
+if sys.version_info < (3, 12):
+    sys.exit(f"pipeline.py needs Python 3.12 or newer, this is {sys.version.split()[0]}")
+
 sys.path.insert(0, str(Path(__file__).parent))
 from common import ArtifactLockBusy, artifact_lock, hold_artifact_lock
 

tests/test_audit_regressions.py

@@ -76,6 +76,39 @@ class ReadmeRegressions(unittest.TestCase):
         unknown = advertised - supported
         self.assertEqual(unknown, set(), f"README advertises unknown flags: {unknown}")
 
+    def test_the_build_version_is_the_one_the_pipeline_requires(self):
+        """"Python 3 + pyyaml" sent a 3.8 user to a SyntaxError in
+        generate_pack, and a 3.10 one through six steps to fail at step 7."""
+        floor = re.search(
+            r"sys\.version_info < \((\d+), (\d+)\)",
+            (ROOT / "scripts" / "pipeline.py").read_text(encoding="utf-8"),
+        )
+        self.assertIsNotNone(floor, "pipeline.py checks no interpreter version")
+        version = f"Python {floor.group(1)}.{floor.group(2)}"
+        for page in ("README.md", "wiki/tools.md", "wiki/testing-guide.md"):
+            with self.subTest(page=page):
+                self.assertIn(version, (ROOT / page).read_text(encoding="utf-8"))
+        self.assertIn(
+            version, (ROOT / "scripts" / "generate_readme.py").read_text(encoding="utf-8")
+        )
+
+    def test_an_older_interpreter_is_refused_before_the_first_step(self):
+        import shutil  # noqa: PLC0415
+
+        python38 = shutil.which("python3.8")
+        if python38 is None:
+            if os.environ.get("CI"):
+                self.fail("CI must provide python3.8")
+            self.skipTest("no python3.8 on PATH")
+        # --help: without the guard the run must stop at argparse, not
+        # rebuild database.json under an interpreter missing pyyaml.
+        proc = subprocess.run(
+            [python38, "-I", "scripts/pipeline.py", "--help"],
+            cwd=ROOT, capture_output=True, text=True, timeout=60, check=False,
+        )
+        self.assertEqual(proc.returncode, 1)
+        self.assertIn("needs Python 3.12", proc.stderr)
+
 
 class ReleaseSigningRegressions(unittest.TestCase):
     """A checksum list published beside its own artifacts proves nothing.

wiki/testing-guide.md

@@ -38,7 +38,7 @@ python -m unittest tests.test_site_exports -v
 python -m unittest tests.test_site_validation -v
 ```
 
-Running the build needs `pyyaml` alone, and so does most of the suite. The
+Running the build needs Python 3.12 and `pyyaml` alone, and so does most of the suite. The
 schema contract tests also need `jsonschema[format-nongpl]`, which the CI
 installs: without it they are reported as skipped, so install it before a pull
 request that touches a profile, a platform file or a schema

wiki/tools.md

@@ -1,7 +1,8 @@
 # Tools - RetroBIOS
 
-All tools are Python scripts in `scripts/`. They depend on `pyyaml`; only
-`validate_schemas.py` also needs `jsonschema[format-nongpl]`.
+All tools are Python scripts in `scripts/`. They need Python 3.12 and `pyyaml`;
+only `validate_schemas.py` also needs `jsonschema[format-nongpl]`. `install.py`
+alone runs on Python 3.8.
 
 ## Pipeline