Automatically clean up stale files on TS build error

.buildkite/windows/entrypoint.bat

@@ -8,7 +8,15 @@ if exist \bazel\node_modules (
 )
 
 call %BAZEL% test %BUILDARGS% ...
-IF %ERRORLEVEL% NEQ 0 exit /B 1
+IF %ERRORLEVEL% NEQ 0 (
+    echo checking ts build
+    call %BAZEL% build //ts/... || (
+        echo ts build failed, cleaning up build products
+        call %BAZEL% run tools:cleanup_js
+    )
+
+    exit /B 1
+)
 
 echo --- Cleanup
 move node_modules \bazel\node_modules

docs/windows.md

@@ -82,6 +82,15 @@ To run Anki in optimized mode, use:
 .\tools\runopt
 ```
 
+## Stale TS Files
+
+The build process may break when .ts files are removed or renamed on Windows. If you're
+tracking Anki's development and you run into a TS build error, try the following:
+
+```
+bazel run tools:cleanup_js
+```
+
 ## More
 
 For info on running tests, building wheels and so on, please see

tools/BUILD.bazel

@@ -5,3 +5,8 @@ py_binary(
     stamp = 1,
     visibility = ["//visibility:public"],
 )
+
+py_binary(
+    name = "cleanup_js",
+    srcs = ["cleanup_js.py"],
+)

tools/cleanup_js.py

@@ -0,0 +1,32 @@
+# Copyright: Ankitects Pty Ltd and contributors
+# License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
+
+# Because Bazel doesn't support building on a sandbox on Windows, our TypeScript
+# outputs are not getting properly tracked. When a ts file is renamed or removed,
+# the old build product is not automatically cleaned up, and that leads to a
+# build failure until the stale outputs are manually removed. This script runs
+# through the output folder, and removes all .ts/.js files to unbreak the build.
+
+import os
+from pathlib import Path
+from typing import Iterable
+import stat
+
+root = Path(os.environ["BUILD_WORKSPACE_DIRECTORY"])
+out_base = root / ".bazel" / "out"
+
+
+def dts_and_js_files(path: Path) -> Iterable[Path]:
+    for entry in path.iterdir():
+        if "runfiles" in entry.name:
+            continue
+        elif entry.is_dir():
+            yield from dts_and_js_files(entry.resolve())
+        elif entry.suffix in (".ts", ".js") and not entry.name.startswith("_"):
+            yield entry.resolve()
+
+
+for output_folder in out_base.glob("*windows*/bin/ts"):
+    for path in dts_and_js_files(output_folder):
+        path.chmod(stat.S_IWRITE)
+        path.unlink()