Store package build logs as circleci artifacts (#1646)

.circleci/config.yml

@@ -131,6 +131,9 @@ jobs:
       - store_artifacts:
           path: /root/repo/build/
 
+      - store_artifacts:
+          path: /root/repo/packages/build-logs
+
   test-core-firefox:
     <<: *defaults
     steps:

.gitignore

@@ -25,4 +25,5 @@ geckodriver.log
 node_modules
 packages/.artifacts
 packages/*/build.log
+packages/build-logs
 dist/

packages/Makefile

@@ -8,8 +8,10 @@ else
 endif
 
 all: .artifacts/bin/pyodide-build
+	mkdir -p build-logs
 	PYTHONPATH="$(PYODIDE_LIBRARIES)/lib/python:$(PYODIDE_ROOT)/pyodide-build/" pyodide-build buildall . ../build \
-		--target=$(TARGETPYTHONROOT) $(ONLY_PACKAGES) --install-dir $(PYODIDE_LIBRARIES) --n-jobs $${PYODIDE_JOBS:-4}
+		--target=$(TARGETPYTHONROOT) $(ONLY_PACKAGES) --install-dir $(PYODIDE_LIBRARIES) --n-jobs $${PYODIDE_JOBS:-4} \
+		--log-dir=build-logs
 
 .artifacts/bin/pyodide-build: ../pyodide-build/pyodide_build/**
 	mkdir -p $(PYODIDE_LIBRARIES)

pyodide-build/pyodide_build/buildall.py

@@ -81,7 +81,7 @@ class Package(BasePackage):
         self.dependents = set()
 
     def build(self, outputdir: Path, args) -> None:
-        with open(self.pkgdir / "build.log", "w") as f:
+        with open(self.pkgdir / "build.log.tmp", "w") as f:
             p = subprocess.run(
                 [
                     sys.executable,
@@ -105,6 +105,27 @@ class Package(BasePackage):
                 stderr=subprocess.STDOUT,
             )
 
+        # Don't overwrite build log if we didn't build the file.
+        # If the file didn't need to be rebuilt, the log will have exactly two lines.
+        rebuilt = True
+        with open(self.pkgdir / "build.log.tmp", "r") as f:
+            try:
+                next(f)
+                next(f)
+                next(f)
+            except StopIteration:
+                rebuilt = False
+
+        if rebuilt:
+            shutil.move(self.pkgdir / "build.log.tmp", self.pkgdir / "build.log")  # type: ignore
+        else:
+            (self.pkgdir / "build.log.tmp").unlink()
+
+        if args.log_dir:
+            shutil.copy(
+                self.pkgdir / "build.log", Path(args.log_dir) / f"{self.name}.log"
+            )
+
         try:
             p.check_returncode()
         except subprocess.CalledProcessError:
@@ -337,6 +358,14 @@ def make_parser(parser):
             "needed if you want to build other packages that depend on this one."
         ),
     )
+    parser.add_argument(
+        "--log-dir",
+        type=str,
+        dest="log_dir",
+        nargs="?",
+        default=None,
+        help=("Directory to place log files"),
+    )
     parser.add_argument(
         "--only",
         type=str,