Automatically rebuild packages if any patches or extra files change

Makefile

@@ -221,8 +221,10 @@ $(CLAPACK): $(CPYTHONLIB)
 	make -C CLAPACK
 
 
-build/packages.json: $(CPYTHONLIB) $(CLAPACK)
+build/packages.json: FORCE
 	make -C packages
 
 emsdk/emsdk/.complete:
 	make -C emsdk
+
+FORCE:

pyodide_build/buildall.py

@@ -19,9 +19,7 @@ def build_package(pkgname, dependencies, packagesdir, outputdir, args):
     # Make sure all of the package's requirements are built first
     for req in reqs:
         build_package(req, dependencies, packagesdir, outputdir, args)
-    if not (packagesdir / pkgname / 'build' / '.packaged').is_file():
-        print("BUILDING PACKAGE: " + pkgname)
-        buildpkg.build_package(packagesdir / pkgname / 'meta.yaml', args)
+    buildpkg.build_package(packagesdir / pkgname / 'meta.yaml', args)
     shutil.copyfile(
         packagesdir / pkgname / 'build' / (pkgname + '.data'),
         outputdir / (pkgname + '.data'))

pyodide_build/buildpkg.py

@@ -147,16 +147,41 @@ def package_files(buildpath, srcpath, pkg, args):
         fd.write(b'\n')
 
 
+def needs_rebuild(pkg, path, buildpath):
+    """
+    Determines if a package needs a rebuild because its meta.yaml, patches, or
+    sources are newer than the `.packaged` thunk.
+    """
+    packaged_token = buildpath / '.packaged'
+    if not packaged_token.is_file():
+        return True
+
+    package_time = packaged_token.stat().st_mtime
+
+    def source_files():
+        yield path
+        yield from pkg.get('source', {}).get('patches', [])
+        yield from (x[0] for x in pkg.get('source', {}).get('extras', []))
+
+    for source_file in source_files():
+        source_file = Path(source_file)
+        if source_file.stat().st_mtime > package_time:
+            return True
+
+
 def build_package(path, args):
     pkg = common.parse_package(path)
     packagedir = pkg['package']['name'] + '-' + pkg['package']['version']
     dirpath = path.parent
     orig_path = Path.cwd()
     os.chdir(dirpath)
+    buildpath = dirpath / 'build'
     try:
-        buildpath = dirpath / 'build'
-        if not buildpath.resolve().is_dir():
-            os.makedirs(buildpath)
+        if not needs_rebuild(pkg, path, buildpath):
+            return
+        if buildpath.resolve().is_dir():
+            shutil.rmtree(buildpath)
+        os.makedirs(buildpath)
         srcpath = download_and_extract(buildpath, packagedir, pkg, args)
         patch(path, srcpath, pkg, args)
         compile(path, srcpath, pkg, args)