pw_package: Forbid some packages in downstream

Some packages are only installed as packages in upstream Pigweed because
upstream Pigweed doesn't have submodules. Projects using Pigweed should
be using submodules to include these packages. Make it a little harder
to use these packages in downstream projects.

Bug: b/249829950
Change-Id: I6eda3dbfb7488bd277df96bd73a00e466bbfe7d3
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/117834
Pigweed-Auto-Submit: Rob Mohr <[email protected]>
Reviewed-by: Alexei Frolov <[email protected]>
Commit-Queue: Auto-Submit <[email protected]>

pw_package/docs.rst

@@ -21,7 +21,8 @@ In general, these should not be used by projects using Pigweed. Pigweed uses
 these packages to avoid using submodules so downstream projects don't have
 multiple copies of a given repository in their source tree. Projects using
 Pigweed should use submodules instead of packages because submodules are
-supported by much more mature tooling: git.
+supported by much more mature tooling: git. To install these packages anyway,
+use ``--force`` on the command line or ``force=True`` in Python code.
 
 -----
 Usage

pw_package/py/pw_package/git_repo.py

@@ -58,6 +58,7 @@ def __init__(
         self._commit = commit
         self._tag = tag
         self._sparse_list = sparse_list
+        self._allow_use_in_downstream = False
 
     def status(self, path: pathlib.Path) -> bool:
         # TODO(tonymd): Check the correct SHA is checked out here.

pw_package/py/pw_package/package_manager.py

@@ -32,11 +32,16 @@ class Package:
 
     def __init__(self, name):
         self._name = name
+        self._allow_use_in_downstream = True
 
     @property
     def name(self):
         return self._name
 
+    @property
+    def allow_use_in_downstream(self):
+        return self._allow_use_in_downstream
+
     def install(
         self, path: pathlib.Path
     ) -> None:  # pylint: disable=no-self-use
@@ -83,6 +88,14 @@ class Packages:
     available: Tuple[str, ...]
 
 
+class UpstreamOnlyPackageError(Exception):
+    def __init__(self, pkg_name):
+        super().__init__(
+            f'Package {pkg_name} is an upstream-only package--it should be '
+            'imported as a submodule and not a package'
+        )
+
+
 class PackageManager:
     """Install and remove optional packages."""
 
@@ -91,7 +104,23 @@ def __init__(self, root: pathlib.Path):
         os.makedirs(root, exist_ok=True)
 
     def install(self, package: str, force: bool = False) -> None:
+        """Install the named package.
+
+        Args:
+            package: The name of the package to install.
+            force: Install the package regardless of whether it's already
+                installed or if it's not "allowed" to be installed on this
+                project.
+        """
+
         pkg = _PACKAGES[package]
+        if not pkg.allow_use_in_downstream:
+            if os.environ.get('PW_ROOT') != os.environ.get('PW_PROJECT_ROOT'):
+                if force:
+                    _LOG.warning(str(UpstreamOnlyPackageError(pkg.name)))
+                else:
+                    raise UpstreamOnlyPackageError(pkg.name)
+
         if force:
             self.remove(package)
         pkg.install(self._pkg_root / pkg.name)

pw_package/py/pw_package/packages/boringssl.py

@@ -40,6 +40,7 @@ def __init__(self, *args, **kwargs):
             ),
             commit='9f55d972854d0b34dae39c7cd3679d6ada3dfd5b',
         )
+        self._allow_use_in_downstream = False
 
     def status(self, path: pathlib.Path) -> bool:
         if not self._boringssl.status(boringssl_repo_path(path)):

pw_presubmit/py/pw_presubmit/build.py

@@ -103,7 +103,9 @@ def bazel(ctx: PresubmitContext, cmd: str, *args: str) -> None:
         raise exc
 
 
-def install_package(ctx: PresubmitContext, name: str) -> None:
+def install_package(
+    ctx: PresubmitContext, name: str, force: bool = False
+) -> None:
     """Install package with given name in given path."""
     root = ctx.package_root
     mgr = package_manager.PackageManager(root)
@@ -114,8 +116,8 @@ def install_package(ctx: PresubmitContext, name: str) -> None:
             'configuration module'
         )
 
-    if not mgr.status(name):
-        mgr.install(name)
+    if not mgr.status(name) or force:
+        mgr.install(name, force=force)
 
 
 def _gn_value(value) -> str: