make toolchain hermetic in case when secondary cache is used

Author: DoDoENT

bazel/emscripten_build_file.bzl

@@ -18,6 +18,13 @@ filegroup(
     ]),
 )
 
+filegroup(
+    name = "builtin_cache",
+    srcs = glob([
+        "emscripten/cache/**",
+    ]),
+)
+
 filegroup(
     name = "emcc_common",
     srcs = [

bazel/emscripten_cache.bzl

@@ -3,6 +3,21 @@ package(default_visibility = ['//visibility:public'])
 exports_files(['emscripten_config'])
 """
 
+BUILD_FILE_USE_BUILTIN_CACHE = """
+alias(
+    name = "emscripten_cache",
+    actual = "{}//:builtin_cache",
+)
+"""
+
+BUILD_FILE_USE_SECONDARY_CACHE = """
+filegroup(
+    name = "emscripten_cache",
+    srcs = glob(["cache/**"]),
+    visibility = ["//visibility:public"],
+)
+"""
+
 EMBUILDER_CONFIG_TEMPLATE = """
 CACHE = '{cache}'
 BINARYEN_ROOT = '{binaryen_root}'
@@ -29,6 +44,26 @@ def get_root_and_script_ext(repository_ctx):
     else:
         fail("Unsupported operating system")
 
+def get_bin_deps_repo_name(repository_ctx):
+    if repository_ctx.os.name.startswith("linux"):
+        if "amd64" in repository_ctx.os.arch or "x86_64" in repository_ctx.os.arch:
+            return "@emscripten_bin_linux"
+        elif "aarch64" in repository_ctx.os.arch:
+            return "@emscripten_bin_linux_arm64"
+        else:
+            fail("Unsupported architecture for Linux")
+    elif repository_ctx.os.name.startswith("mac"):
+        if "amd64" in repository_ctx.os.arch or "x86_64" in repository_ctx.os.arch:
+            return "@emscripten_bin_mac"
+        elif "aarch64" in repository_ctx.os.arch:
+            return "@emscripten_bin_mac_arm64"
+        else:
+            fail("Unsupported architecture for MacOS")
+    elif repository_ctx.os.name.startswith("windows"):
+        return "@emscripten_bin_win"
+    else:
+        fail("Unsupported operating system")
+
 def _emscripten_cache_repository_impl(repository_ctx):
     # Read the default emscripten configuration file
     default_config = repository_ctx.read(
@@ -38,6 +73,8 @@ def _emscripten_cache_repository_impl(repository_ctx):
     )
 
     repo_metadata = None
+    build_file_content = BUILD_FILE_CONTENT_TEMPLATE
+    use_builtin_cache = True
 
     if repository_ctx.attr.prebuilt_cache_url:
         repository_ctx.download_and_extract(
@@ -48,8 +85,7 @@ def _emscripten_cache_repository_impl(repository_ctx):
         )
 
         # Use the prebuilt cache
-        prebuilt_cache_path = repository_ctx.path("cache")
-        default_config += "CACHE = '{}'\n".format(prebuilt_cache_path)
+        use_builtin_cache = False
 
         repo_metadata = repository_ctx.repo_metadata(reproducible = True)
 
@@ -90,12 +126,17 @@ def _emscripten_cache_repository_impl(repository_ctx):
         if result.return_code != 0:
             fail("Embuilder exited with a non-zero return code")
 
-        # Override Emscripten's cache with the secondary cache
-        default_config += "CACHE = '{}'\n".format(cache)
+        use_builtin_cache = False
+
+    if use_builtin_cache:
+        build_file_content += BUILD_FILE_USE_BUILTIN_CACHE.format(get_bin_deps_repo_name(repository_ctx))
+    else:
+        default_config += 'CACHE = os.path.join(os.path.dirname(os.environ["EM_CONFIG_PATH"]), "cache")\n'
+        build_file_content += BUILD_FILE_USE_SECONDARY_CACHE
 
     # Create the configuration file for the toolchain and export
     repository_ctx.file("emscripten_config", default_config)
-    repository_ctx.file("BUILD.bazel", BUILD_FILE_CONTENT_TEMPLATE)
+    repository_ctx.file("BUILD.bazel", build_file_content)
 
     return repo_metadata
 

bazel/remote_emscripten_repository.bzl

@@ -59,6 +59,7 @@ def create_toolchains(name, repo_name, exec_compatible_with):
         name = common_files_name,
         srcs = [
             "@emscripten_cache//:emscripten_config",
+            "@emscripten_cache//:emscripten_cache",
             "@emsdk//emscripten_toolchain:env.sh",
             "@emsdk//emscripten_toolchain:env.bat",
             "@nodejs//:node_files",