More thorough compile_commands.json generation

build.py

@@ -86,6 +86,25 @@ def expand_json_file(sourcefile, outputfile, config):
     expanded = expand_json(data, vars(config))
     Path(outputfile).write_text(json.dumps(expanded, indent=4))
 
+#
+# Extracting a generated module file.
+#
+
+def cpp_files_included_by(module):
+    """
+    Given the name of a Module.XYZ.cpp file generated by unreal
+    build tool, scan the module for include directives that include
+    another C++ file.  Produce a list of these C++ files.
+    """
+    result = []
+    for line in Path(module).read_text().splitlines():
+        if line.startswith("#include "):
+            file = line[9:].strip().strip('"')
+            if file.endswith(".cpp"):
+                result.append(file)
+    return result
+
+
 #
 # Applying patches to files with DOS line endings.
 #
@@ -293,6 +312,9 @@ def build_intellisense_database_for_clangd():
         cpp = rsp.removesuffix(".o.rsp")
         args = [clang, "@"+rsp]
         ccjson.append({ "file" : cpp, "arguments":args, "directory":ccdir })
+        for subfile in cpp_files_included_by(cpp):
+            abs = os.path.join(f"{UNREALENGINE}/Engine", subfile)
+            ccjson.append({ "file" : abs, "arguments":args, "directory":ccdir })
     Path(f"{INTEGRATION}/.vscode/compile_commands.json").write_text(json.dumps(ccjson, indent=2))