pw_build: Allow cc_blob_library to handle relative paths

cc_blob_library currently sets every path to the absolute
path but for RBE all paths must come from the build root
and not absolute paths.  This change will allow for
everything to be based off the build root.

Bug: b/239560853
Test: Verified this generated the build files correct and built
      correctly with RBE and regular builds.
Change-Id: I224e60e3c68a6018de0dc747f2620a8897f78613
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/98441
Reviewed-by: Tom Turney <tturney@google.com>
Reviewed-by: Joe Brennan <jmbrenna@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
Pigweed-Auto-Submit: Joe Brennan <jmbrenna@google.com>
Reviewed-by: Armando Montanez <amontanez@google.com>

pw_build/cc_blob_library.cmake

@@ -134,7 +134,6 @@ function(pw_cc_blob_library NAME)
       python3
       "$ENV{PW_ROOT}/pw_build/py/pw_build/generate_cc_blob_library.py"
       --blob-file "${blob_json_file}"
-      --header-include "${arg_HEADER}"
       --out-header "${generated_header}"
       --out-source "${generated_source}"
       --namespace "${arg_NAMESPACE}"

pw_build/cc_blob_library.gni

@@ -53,9 +53,9 @@ template("pw_cc_blob_library") {
   foreach(blob, invoker.blobs) {
     assert(defined(blob.symbol_name), "Each 'blob' requires a 'symbol_name'")
     assert(defined(blob.file_path), "Each 'blob' requires a 'file_path'")
-    blob.file_path = rebase_path(blob.file_path)
-    _blobs += [ blob ]
     _blob_files += [ blob.file_path ]
+    blob.file_path = rebase_path(blob.file_path, root_build_dir)
+    _blobs += [ blob ]
   }
 
   _out_dir = "$target_gen_dir/$target_name"
@@ -78,7 +78,6 @@ template("pw_cc_blob_library") {
       "--blob-file",
       rebase_path(_blob_json_file, root_build_dir),
       "--namespace=${invoker.namespace}",
-      "--header-include=${invoker.out_header}",
       "--out-header",
       rebase_path(_header, root_build_dir),
       "--out-source",

pw_build/py/generate_cc_blob_library_test.py

@@ -40,7 +40,7 @@
 
 COMMON_SOURCE_START = COMMENT + """\
 
-#include "path/to/header.h"
+#include "header.h"
 
 #include <array>
 #include <cstddef>
@@ -166,7 +166,7 @@ def test_source_with_mixed_blobs(self):
         ]
 
         source = generate_cc_blob_library.source_from_blobs(
-            blobs, 'path/to/header.h')
+            blobs, 'path/to/header.h', 'path/to/source.cc')
         expected_source = (f'{COMMON_SOURCE_START}'
                            '\n'
                            '\n'
@@ -183,7 +183,7 @@ def test_source_with_namespace(self):
         blobs = [generate_cc_blob_library.Blob('fooBlob', foo_blob, None)]
 
         source = generate_cc_blob_library.source_from_blobs(
-            blobs, 'path/to/header.h', 'pw::foo')
+            blobs, 'path/to/header.h', 'path/to/source.cc', 'pw::foo')
         expected_source = (f'{COMMON_SOURCE_START}'
                            '\n'
                            'namespace pw::foo {\n'
@@ -206,7 +206,7 @@ def test_source_with_linker_sections(self):
         ]
 
         source = generate_cc_blob_library.source_from_blobs(
-            blobs, 'path/to/header.h')
+            blobs, 'path/to/header.h', 'path/to/source.cc')
         expected_source = (f'{COMMON_SOURCE_START}'
                            '\n'
                            '\n'
@@ -230,7 +230,7 @@ def test_source_with_alignas(self):
         ]
 
         source = generate_cc_blob_library.source_from_blobs(
-            blobs, 'path/to/header.h')
+            blobs, 'path/to/header.h', 'path/to/source.cc')
         expected_source = (f'{COMMON_SOURCE_START}'
                            '\n'
                            '\n'

pw_build/py/pw_build/generate_cc_blob_library.py

@@ -16,6 +16,7 @@
 import argparse
 import itertools
 import json
+import os
 from pathlib import Path
 from string import Template
 import textwrap
@@ -90,9 +91,6 @@ def parse_args() -> dict:
                         required=True,
                         help=('Path to json file containing the list of blobs '
                               'to generate.'))
-    parser.add_argument('--header-include',
-                        required=True,
-                        help='Path to use in #includes for the header')
     parser.add_argument('--out-source',
                         type=Path,
                         required=True,
@@ -147,7 +145,6 @@ def array_def_from_blob_data(blob: Blob, blob_data: bytes) -> str:
         section_attr = ''
 
     byte_strs = ['std::byte{{0x{:02X}}}'.format(b) for b in blob_data]
-
     lines = []
     for byte_strs_for_line in split_into_chunks(byte_strs, BYTES_PER_LINE):
         bytes_segment = ', '.join(byte_strs_for_line)
@@ -162,9 +159,13 @@ def array_def_from_blob_data(blob: Blob, blob_data: bytes) -> str:
 
 
 def source_from_blobs(blobs: Iterable[Blob],
-                      header_path: str,
+                      header_path: Path,
+                      source_path: Path,
                       namespace: Optional[str] = None) -> str:
     """Generate the contents of a C++ source file from blobs."""
+    header_path = Path(
+        os.path.relpath(header_path,
+                        os.path.commonprefix([header_path, source_path])))
     lines = [SOURCE_PREFIX_TEMPLATE.substitute(header_path=header_path)]
     if namespace:
         lines.append(NAMESPACE_OPEN_TEMPLATE.substitute(namespace=namespace))
@@ -183,17 +184,16 @@ def load_blobs(blob_file: Path) -> Sequence[Blob]:
 
 
 def main(blob_file: Path,
-         header_include: str,
          out_source: Path,
          out_header: Path,
          namespace: Optional[str] = None) -> None:
     blobs = load_blobs(blob_file)
 
     out_header.parent.mkdir(parents=True, exist_ok=True)
     out_header.write_text(header_from_blobs(blobs, namespace))
-
     out_source.parent.mkdir(parents=True, exist_ok=True)
-    out_source.write_text(source_from_blobs(blobs, header_include, namespace))
+    out_source.write_text(
+        source_from_blobs(blobs, out_header, out_source, namespace))
 
 
 if __name__ == '__main__':