fbcode_builder: per-package --extra-cmake-defines for GHA generator

Summary:
Add --package-extra-cmake-defines PACKAGE=JSON to generate-github-actions
so a generated workflow can pin defines to a single dependency's build
step (e.g. THRIFT_SERIALIZATION_ONLY=ON only for fbthrift) without
applying them to every other dep. Multiple uses accumulate; the value
must be a JSON object.

Also reorder the cmake builder so caller-supplied extra_cmake_defines
apply *after* the --shared-libs defaults. Without this, a per-package
override cannot turn BUILD_SHARED_LIBS back off for a specific
dependency in a mostly-shared build, which is the main reason the
per-package flag exists.

Reviewed By: bigfootjon

Differential Revision: D103767906

fbshipit-source-id: da61d3c30b8e6f7111c75de9fc48d975b1e954c9

Author: r-barnes

build/fbcode_builder/getdeps.py

@@ -1252,12 +1252,16 @@ def write_job_for_platform(self, platform, args):  # noqa: C901
                 out.write('        version: "v0.14.0"\n')
                 extra_cmake_defines["CMAKE_CXX_COMPILER_LAUNCHER"] = "sccache"
 
-            if extra_cmake_defines:
-                extra_cmake_arg = (
-                    " --extra-cmake-defines '" + json.dumps(extra_cmake_defines) + "'"
-                )
-            else:
-                extra_cmake_arg = ""
+            per_package_defines = _parse_per_package_defines(
+                getattr(args, "package_extra_cmake_defines", []) or []
+            )
+
+            def cmake_arg_for(name):
+                merged = dict(extra_cmake_defines)
+                merged.update(per_package_defines.get(name, {}))
+                if merged:
+                    return " --extra-cmake-defines '" + json.dumps(merged) + "'"
+                return ""
 
             build_type_arg = ""
             if override_build_type:
@@ -1396,7 +1400,7 @@ def write_job_for_platform(self, platform, args):  # noqa: C901
                             f"      if: ${{{{ steps.paths.outputs.{m.name}_SOURCE }}}}\n"
                         )
                 out.write(
-                    f"      run: {getdepscmd}{allow_sys_arg} build {build_type_arg}{src_dir_arg}{free_up_disk}--no-tests {m.name}{extra_cmake_arg}\n"
+                    f"      run: {getdepscmd}{allow_sys_arg} build {build_type_arg}{src_dir_arg}{free_up_disk}--no-tests {m.name}{cmake_arg_for(m.name)}\n"
                 )
 
                 if args.use_build_cache and not src_dir_arg:
@@ -1437,7 +1441,7 @@ def write_job_for_platform(self, platform, args):  # noqa: C901
                 no_deps_arg = "--no-deps "
 
             out.write(
-                f"      run: {getdepscmd}{allow_sys_arg} build {build_type_arg}{tests_arg}{no_deps_arg}--src-dir=. {manifest.name}{project_prefix}{extra_cmake_arg}\n"
+                f"      run: {getdepscmd}{allow_sys_arg} build {build_type_arg}{tests_arg}{no_deps_arg}--src-dir=. {manifest.name}{project_prefix}{cmake_arg_for(manifest.name)}\n"
             )
 
             if use_sccache:
@@ -1569,6 +1573,45 @@ def setup_project_cmd_parser(self, parser):
             dest="use_build_cache",
             help="Do not attempt to use the build cache.",
         )
+        parser.add_argument(
+            "--package-extra-cmake-defines",
+            action="append",
+            default=[],
+            metavar="PACKAGE=JSON",
+            help=(
+                "Add cmake defines that apply only to the named package's "
+                "build step in the generated workflow. Example: "
+                "--package-extra-cmake-defines "
+                '\'fbthrift={"THRIFT_SERIALIZATION_ONLY":"ON"}\'. May be '
+                "passed multiple times."
+            ),
+        )
+
+
+def _parse_per_package_defines(values):
+    """Parse a list of `package=json` strings into a dict of dicts."""
+    result = {}
+    for entry in values or []:
+        if "=" not in entry:
+            raise SystemExit(
+                f"--package-extra-cmake-defines value {entry!r} must be of the "
+                "form PACKAGE=JSON"
+            )
+        package, raw = entry.split("=", 1)
+        try:
+            parsed = json.loads(raw)
+        except json.JSONDecodeError as e:
+            raise SystemExit(
+                f"--package-extra-cmake-defines for {package!r} is not valid "
+                f"JSON: {e}"
+            )
+        if not isinstance(parsed, dict):
+            raise SystemExit(
+                f"--package-extra-cmake-defines for {package!r} must be a JSON "
+                "object"
+            )
+        result.setdefault(package, {}).update(parsed)
+    return result
 
 
 def get_arg_var_name(args):

build/fbcode_builder/getdeps/builder.py

@@ -782,8 +782,6 @@ def __init__(
             final_install_prefix=final_install_prefix,
         )
         self.defines: dict[str, str] = defines or {}
-        if extra_cmake_defines:
-            self.defines.update(extra_cmake_defines)
         self.cmake_targets: list[str] = cmake_targets or ["install"]
 
         if build_opts.is_windows():
@@ -799,6 +797,14 @@ def __init__(
             self.defines["BUILD_SHARED_LIBS"] = "ON"
             self.defines["BOOST_LINK_STATIC"] = "OFF"
 
+        # Apply caller-supplied extra defines last so a per-package
+        # --extra-cmake-defines can override defaults (notably
+        # BUILD_SHARED_LIBS=ON set by --shared-libs above), letting a
+        # single workflow build most projects shared while pinning a
+        # specific dependency to static.
+        if extra_cmake_defines:
+            self.defines.update(extra_cmake_defines)
+
     def _invalidate_cache(self) -> None:
         for name in [
             "CMakeCache.txt",