[tools] Add cmake_configure_files (plural) macro

This is important when configuring multiple files with the same
bag of definitions, so `strict = True` mode still makes sense.

Improve the diagnostic output to show *all* missing definitions, not
just the first one. This helps a lot during Local development.

tools/workspace/cmake_configure_file.bzl

@@ -5,12 +5,13 @@ load(
 
 # Defines the implementation actions to cmake_configure_file.
 def _cmake_configure_file_impl(ctx):
-    arguments = [
-        "--input",
-        ctx.file.src.path,
-        "--output",
-        ctx.outputs.out.path,
-    ]
+    if len(ctx.files.srcs) != len(ctx.outputs.outs):
+        fail("The number of srcs and outs must be congruent")
+    arguments = []
+    for src in ctx.files.srcs:
+        arguments += ["--input", src.path]
+    for out in ctx.outputs.outs:
+        arguments += ["--output", out.path]
     for item in ctx.attr.defines:
         arguments += ["-D" + item]
     for item in ctx.attr.undefines:
@@ -20,8 +21,8 @@ def _cmake_configure_file_impl(ctx):
     if ctx.attr.strict:
         arguments += ["--strict"]
     ctx.actions.run(
-        inputs = [ctx.file.src] + ctx.files.cmakelists,
-        outputs = [ctx.outputs.out],
+        inputs = ctx.files.srcs + ctx.files.cmakelists,
+        outputs = ctx.outputs.outs,
         arguments = arguments,
         env = ctx.attr.env,
         executable = ctx.executable.cmake_configure_file_py,
@@ -31,11 +32,8 @@ def _cmake_configure_file_impl(ctx):
 # Defines the rule to cmake_configure_file.
 _cmake_configure_file_gen = rule(
     attrs = {
-        "src": attr.label(
-            allow_single_file = True,
-            mandatory = True,
-        ),
-        "out": attr.output(mandatory = True),
+        "srcs": attr.label_list(allow_files = True, mandatory = True),
+        "outs": attr.output_list(mandatory = True),
         "defines": attr.string_list(),
         "undefines": attr.string_list(),
         "cmakelists": attr.label_list(allow_files = True),
@@ -90,8 +88,35 @@ def cmake_configure_file(
     """
     _cmake_configure_file_gen(
         name = name,
-        src = src,
-        out = out,
+        srcs = [src],
+        outs = [out],
+        defines = defines,
+        undefines = undefines,
+        cmakelists = cmakelists,
+        strict = strict,
+        env = hermetic_python_env(),
+        **kwargs
+    )
+
+def cmake_configure_files(
+        name,
+        srcs = None,
+        outs = None,
+        defines = None,
+        undefines = None,
+        cmakelists = None,
+        strict = None,
+        **kwargs):
+    """Like cmake_configure_file(), but with itemwise pairs of srcs => outs,
+    instead of just one pair of src => out.
+
+    When in strict mode, the defines / undefines must be used by *at least one*
+    of the srcs; only a definition that is unused by all srcs is an error.
+    """
+    _cmake_configure_file_gen(
+        name = name,
+        srcs = srcs,
+        outs = outs,
         defines = defines,
         undefines = undefines,
         cmakelists = cmakelists,

tools/workspace/cmake_configure_file.py

@@ -53,8 +53,7 @@ def _transform(*, line, definitions, strict):
         if var not in definitions:
             defined = False
             if strict:
-                raise KeyError(f"Missing define or undefine decision for {var}"
-                               " when running in strict=True mode")
+                raise KeyError(var)
         else:
             defined = definitions[var] is not None
             used_vars.add(var)
@@ -85,7 +84,7 @@ def _transform(*, line, definitions, strict):
         assert len(var) > 0
 
         if var not in definitions:
-            raise KeyError('Missing definition for ' + var)
+            raise KeyError(var)
         used_vars.add(var)
         value = definitions.get(var)
         if value is None:
@@ -147,8 +146,8 @@ def _setup_definitions(args):
 
 def main():
     parser = argparse.ArgumentParser()
-    parser.add_argument('--input', metavar='FILE')
-    parser.add_argument('--output', metavar='FILE')
+    parser.add_argument('--input', metavar='FILE', action='append')
+    parser.add_argument('--output', metavar='FILE', action='append')
     parser.add_argument(
         '-D', metavar='NAME', dest='defines', action='append', default=[])
     parser.add_argument(
@@ -158,27 +157,37 @@ def main():
     parser.add_argument(
         '--strict', action='store_true')
     args = parser.parse_args()
-    if args.input is None or args.output is None:
+    if not (len(args.input) == len(args.output)
+            and len(args.input) > 0):
         parser.print_usage()
         sys.exit(1)
     definitions, cmakelist_keys = _setup_definitions(args)
 
     total_used_vars = set()
-    with open(args.input, 'r') as input_file:
-        with open(args.output + '.tmp', 'w') as output_file:
-            for input_line in input_file.readlines():
-                output_line, used_vars = _transform(
-                    line=input_line,
-                    definitions=definitions,
-                    strict=args.strict)
-                output_file.write(output_line)
-                total_used_vars |= used_vars
+    missing_vars = set()
+    for input_path, output_path in zip(args.input, args.output):
+        with open(input_path, 'r') as input_file:
+            with open(output_path + '.tmp', 'w') as output_file:
+                for input_line in input_file.readlines():
+                    try:
+                        output_line, used_vars = _transform(
+                            line=input_line,
+                            definitions=definitions,
+                            strict=args.strict)
+                        output_file.write(output_line)
+                        total_used_vars |= used_vars
+                    except KeyError as e:
+                        missing_vars.add(e.args[0])
+    if missing_vars:
+        raise RuntimeError(f"The definitions of {sorted(missing_vars)} were"
+                           " required, but missing.")
     unused_vars = definitions.keys() - cmakelist_keys - total_used_vars
     if unused_vars:
         raise RuntimeError(f"The definitions of {sorted(unused_vars)} were"
                            " ignored and therefore seem like dead code;"
                            " remove them from defines= or undefines=.")
-    os.rename(args.output + '.tmp', args.output)
+    for output_path in args.output:
+        os.rename(output_path + '.tmp', output_path)
 
 
 if __name__ == '__main__':