1 files changed, 103 insertions, 0 deletions
diff --git a/llvm_tools/manifest_utils.py b/llvm_tools/manifest_utils.py
new file mode 100644
index 00000000..67eae4f3
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+++ b/llvm_tools/manifest_utils.py
@@ -0,0 +1,103 @@
+# Copyright 2023 The ChromiumOS Authors
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Provides utilities to read and edit the ChromiumOS Manifest entries.
+
+While this code reads and edits the internal manifest, it should only operate
+on toolchain projects (llvm-project, etc.) which are public.
+"""
+
+from pathlib import Path
+import shutil
+import subprocess
+from xml.etree import ElementTree
+
+import atomic_write_file
+
+
+LLVM_PROJECT_PATH = "src/third_party/llvm-project"
+
+
+class FormattingError(Exception):
+    """Error occurred when formatting the manifest."""
+
+    pass
+
+
+class UpdateManifestError(Exception):
+    """Error occurred when updating the manifest."""
+
+    pass
+
+
+def make_xmlparser():
+    """Return a new xmlparser with custom TreeBuilder."""
+    return ElementTree.XMLParser(
+        target=ElementTree.TreeBuilder(insert_comments=True)
+    )
+
+
+def update_chromeos_manifest(revision: str, src_tree: Path) -> Path:
+    """Replaces the manifest project revision with 'revision'.
+
+    Notably, this function reformats the manifest file to preserve
+    the formatting as specified by 'cros format'.
+
+    Args:
+        revision: Revision (git sha) to use in the manifest.
+        src_tree: Path to the root of the source tree checkout.
+
+    Returns:
+        The manifest path.
+
+    Post:
+        The llvm-project revision info in the chromeos repo manifest
+        is updated with 'revision'.
+
+    Raises:
+        UpdateManifestError: The manifest could not be changed.
+        FormattingError: The manifest could not be reformatted.
+    """
+    manifest_path = get_chromeos_manifest_path(src_tree)
+    parser = make_xmlparser()
+    xmltree = ElementTree.parse(manifest_path, parser)
+    update_chromeos_manifest_tree(revision, xmltree.getroot())
+    with atomic_write_file.atomic_write(manifest_path, mode="wb") as f:
+        xmltree.write(f, encoding="UTF-8")
+    format_manifest(manifest_path)
+    return manifest_path
+
+
+def get_chromeos_manifest_path(src_tree: Path) -> Path:
+    """Return the path to the toolchain manifest."""
+    return src_tree / "manifest-internal" / "_toolchain.xml"
+
+
+def update_chromeos_manifest_tree(revision: str, xmlroot: ElementTree.Element):
+    """Update the revision info for LLVM for a manifest XML root."""
+
+    # This exists mostly for testing.
+    def is_llvm_project(child):
+        return (
+            child.tag == "project" and child.attrib["path"] == LLVM_PROJECT_PATH
+        )
+
+    finder = (child for child in xmlroot if is_llvm_project(child))
+    llvm_project_elem = next(finder, None)
+    # Element objects can be falsy, so we need to explicitly check None.
+    if llvm_project_elem is not None:
+        # Update the llvm revision git sha
+        llvm_project_elem.attrib["revision"] = revision
+    else:
+        raise UpdateManifestError("xmltree did not have llvm-project")
+
+
+def format_manifest(repo_manifest: Path):
+    """Use cros format to format the given manifest."""
+    if not shutil.which("cros"):
+        raise FormattingError(
+            "unable to format manifest, 'cros'" " executable not in PATH"
+        )
+    cmd = ["cros", "format", repo_manifest]
+    subprocess.run(cmd, check=True)