pw_env_setup: Add relative_pigweed_root to pigweed.json

Bug: b/300632028
Change-Id: Ib3ba7b98fbbdb05d10dac4611ae30fa5b27eab57
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/171218
Reviewed-by: Ted Pudlik <[email protected]>
Commit-Queue: Auto-Submit <[email protected]>
Pigweed-Auto-Submit: Rob Mohr <[email protected]>
Presubmit-Verified: CQ Bot Account <[email protected]>

pigweed.json

@@ -55,6 +55,7 @@
     },
     "pw_env_setup": {
       "root_variable": "PW_ROOT",
+      "relative_pigweed_root": ".",
       "rosetta": "allow",
       "gni_file": "build_overrides/pigweed_environment.gni",
       "cipd_package_files": [

pw_env_setup/docs.rst

@@ -217,6 +217,11 @@ here.
   use ``PW_PROJECT_ROOT`` instead. (That variable will be set regardless of
   whether this is provided.)
 
+``pw.pw_env_setup.relative_pigweed_root``
+  Location of the Pigweed submodule within the source tree. Optional—environment
+  setup will work correctly without this. If present, will confirm that it's
+  correct. May be used by other tooling.
+
 ``pw.pw_env_setup.cipd_package_files``
   CIPD package file. JSON file consisting of a list of additional CIPD package
   files to import and a list of dictionaries with "path", "platforms", "subdir",

pw_env_setup/py/pw_env_setup/env_setup.py

@@ -295,6 +295,20 @@ def _parse_config_file(self, config_file):
 
         self._root_variable = config.pop('root_variable', None)
 
+        # This variable is not used by env setup since we already have it.
+        # However, other tools may use it, so we double-check that it's correct.
+        pigweed_root = os.path.join(
+            self._project_root,
+            config.pop('relative_pigweed_root', self._pw_root),
+        )
+        if os.path.abspath(self._pw_root) != os.path.abspath(pigweed_root):
+            raise ValueError(
+                'expected Pigweed root {!r} in config but found {!r}'.format(
+                    os.path.relpath(self._pw_root, self._project_root),
+                    os.path.relpath(pigweed_root, self._project_root),
+                )
+            )
+
         rosetta = config.pop('rosetta', 'allow')
         if rosetta not in ('never', 'allow', 'force'):
             raise ValueError(rosetta)