Govern task context and advance execution pointer

tools/web/check-scene-desktop.py

@@ -0,0 +1,54 @@
+#!/usr/bin/env python3
+import hashlib
+import json
+import os
+import pathlib
+import sys
+import tempfile
+
+import bpy
+
+
+def report():
+    scene = bpy.data.scenes.get("WebGapScene")
+    if scene is None:
+        raise RuntimeError("WebGapScene is missing")
+    return {
+        "id": "scene:" + scene.name,
+        "name": scene.name,
+        "frameCurrent": int(scene.frame_current),
+        "frameStart": int(scene.frame_start),
+        "frameEnd": int(scene.frame_end),
+        "fps": round(float(scene.render.fps), 6),
+        "fpsBase": round(float(scene.render.fps_base), 6),
+        "unitSystem": {"NONE": 0, "METRIC": 1, "IMPERIAL": 2}.get(scene.unit_settings.system, -1),
+        "unitScale": round(float(scene.unit_settings.scale_length), 6),
+        "renderEngine": scene.render.engine,
+    }
+
+
+def main():
+    arguments = sys.argv[sys.argv.index("--") + 1 :]
+    if len(arguments) != 2:
+        raise SystemExit("usage: blender -b --python check-scene-desktop.py -- FIXTURE REPORT")
+    fixture, output = (pathlib.Path(value).resolve() for value in arguments)
+    bpy.ops.wm.open_mainfile(filepath=str(fixture), load_ui=False)
+    before = report()
+    descriptor, temporary = tempfile.mkstemp(prefix="m16-scene-reopen-", suffix=".blend", dir=fixture.parent)
+    os.close(descriptor)
+    try:
+        bpy.ops.wm.save_as_mainfile(filepath=temporary, check_existing=False, compress=True)
+        bpy.ops.wm.open_mainfile(filepath=temporary, load_ui=False)
+        after = report()
+    finally:
+        pathlib.Path(temporary).unlink(missing_ok=True)
+    if before != after:
+        raise RuntimeError(f"scene save/reopen drift: {before} != {after}")
+    value = {"schemaVersion": 1, "task": "M16-GAP-00020", "operation": "SCENE_DATABLOCK_DESKTOP", "fixture": str(fixture), "fixtureSha256": hashlib.sha256(fixture.read_bytes()).hexdigest(), "scene": after, "saveReopen": "EXACT", "blenderVersion": bpy.app.version_string}
+    output.parent.mkdir(parents=True, exist_ok=True)
+    output.write_text(json.dumps(value, indent=2, sort_keys=True) + "\n", encoding="utf-8")
+    print(f"scene-desktop-ok id={after['id']} frames={after['frameStart']}-{after['frameEnd']} saveReopen=exact")
+
+
+if __name__ == "__main__":
+    main()