main_v2: Created Script to Fetch Revision Info From Manifest

Summary:
West isn't able to retrieve the revision information
from the manifest before the repo has been updated.

In order to facilitate retrieving dependencies from
alternative locations we need to know the revision first.

This scrip can naively parse the manifest file and print
the requested project revision(s)

Reviewed By: garnermic

Differential Revision: D35794313

fbshipit-source-id: 3bf6a2ba4e5cb597b0f212e7b2210d76b311a44f

Author: GoldenBug

.gitignore

@@ -12,7 +12,7 @@ src/.config
 src/include/config.h
 src/tools/Kconfiglib/__pycache__/kconfiglib.cpython-38.pyc
 *.o
-build
+/build
 
 # Ignore Vim swap files
 *.swp

scripts/build/get_revision.py

@@ -0,0 +1,145 @@
+#!/usr/bin/env python3
+
+import argparse
+import sys
+import re
+
+
+def get_manifest(manifest_path) -> str:
+    """
+    This function reads in the manifest file give the path and checks to
+    see if it has the manifest keyword at the beginning of the line
+    somewhere in the file.
+
+    It then reads in the file as a single string.
+
+    :param manifest_path: The path to a west manifest yml file.
+    :type manifest_path: str
+    :return: String containing the raw file contents.
+    :rtype: str
+    """
+    try:
+        manifest_file = open(manifest_path, "r")
+    except FileNotFoundError:
+        print("Manifest file not found at: " + manifest_path)
+        sys.exit(255)
+    except Exception as e:
+        print("Error opening manifest file.")
+        print(e)
+        sys.exit(255)
+
+    try:
+        file_contents = manifest_file.read()
+    except Exception as e:
+        print("Error reading manifest File Contents.")
+        print(e)
+        sys.exit(255)
+
+    file_match = re.search("\nmanifest:", file_contents)
+    if file_match is None:
+        print("File does not appear to be a manifest file.")
+        print("Missing \"manifest\" key in file.")
+        sys.exit(255)
+
+    return file_contents
+
+
+def parse_revisions(manifest_contents) -> dict:
+    """
+    Parses the contents of the manifest file using a regex and then stores the
+    output of the matches in a dictionary using the project name as the key and
+    the returned revision as the value.
+
+    :param manifest_contents: Raw contents of the manifest file.
+    :type manifest_contents: str
+    :return: Dictionary containing project name and revision as key, values.
+    :rtype: dict
+    """
+    regex_pattern = r"- name:[ ]*([^ \n]*)[\s\S]*?revision:[ ]*([a-z,0-9,\.]*)"
+    matches = re.findall(regex_pattern, manifest_contents, re.M)
+
+    revisions = {}
+    for revision_pair in matches:
+        if revision_pair is not None and len(revision_pair) == 2:
+            revisions[revision_pair[0]] = revision_pair[1]
+
+    return revisions
+
+
+def print_all_revisions(revisions):
+    """
+    If no project name is supplied on the command line this function will be
+    used to print out all project revisions. It will print a single project and
+    it's revision per line.
+
+    :param revisions: A dictionary containing project name and revisions.
+    :type revisions: dict
+    """
+    if len(revisions) == 0:
+        print("No projects and revisions could be parsed from manifest.")
+        sys.exit(255)
+
+    for project, revision in revisions.items():
+        print(project + " " + revision)
+
+
+def print_revision(project, revisions):
+    """
+    Attempts to print the revision for the given project if it exists.
+
+    :param project: The project name to print.
+    :type project: str
+    :param revisions: A dictionary contain project names and revisions.
+    :type revisions: dict
+    """
+    if len(revisions) == 0:
+        print("No projects and revisions could be parsed from manifest.")
+        return
+
+    if project not in revisions:
+        print("Could not find project " + project + " in manifest.")
+        print("Possible projects in manifest with revisions:")
+        for project, revision in revisions.items():
+            print("- " + project)
+        sys.exit(255)
+
+    else:
+        print(revisions[project])
+
+
+def get_revision(project, manifest_path):
+    """
+    Main work function that takes the CLI input and loads the file, parses
+    the revisions, and prints the requested revision(s) if possible.
+
+    :param project: The project name to print, or None if none supplied.
+    :type project: str
+    :param manifest_path: The path to the manifest file to parse.
+    :type manifest_path: str
+    """
+    manifest_contents = get_manifest(manifest_path)
+    project_revisions = parse_revisions(manifest_contents)
+
+    if project is None:
+        print_all_revisions(project_revisions)
+    else:
+        print_revision(project, project_revisions)
+
+
+if __name__ == '__main__':
+    parser = argparse.ArgumentParser(
+        description='Get revision from the specified project')
+
+    parser.add_argument(
+        '-p',
+        '--project',
+        help="The name of the project to retrieve the revision for. "
+        "If this option is not used then all revisions "
+        "will be printed")
+    parser.add_argument(
+        '-m', '--manifest', required=True,
+        help="The path to the west manifest file to parse for the requested "
+        "revision")
+
+    args = parser.parse_args()
+    get_revision(args.project, args.manifest)