Add extra presets (#62)

* Add extra presets

* Add extra test for flags from dict

Author: hofbi

bazelrc-preset.bzl

@@ -53,6 +53,9 @@ def _verify_command_overrides(meta):
     if sets.length(unique_commands) != len(meta):
         fail("Multiple flag overrides use the same command. Make sure flag overrides use different command.")
 
+def _get_flags_from_extra_presets(extra_presets_json):
+    return {key: struct(**value) for key, value in json.decode(extra_presets_json).items()}
+
 def _generate_preset(ctx):
     content = ctx.actions.args().set_param_file_format("multiline")
     content.add_all([
@@ -61,7 +64,7 @@ def _generate_preset(ctx):
         "  bazel run {}.update".format(ctx.label),
     ], format_each = "# %s")
 
-    flags = FLAGS | (MIGRATIONS if ctx.attr.strict else {})
+    flags = FLAGS | (MIGRATIONS if ctx.attr.strict else {}) | _get_flags_from_extra_presets(ctx.attr.extra_presets)
     for flag, meta in flags.items():
         # Syntax sugar: allow a struct to stand in for a singleton list
         if type(meta) != type([]):
@@ -77,6 +80,11 @@ def _generate_preset(ctx):
 generate_preset = rule(
     implementation = _generate_preset,
     attrs = {
+        "extra_presets": attr.string(
+            doc = """\
+            A json encoded string of presets to add to the preset generation matching the format of the FLAGS dictionary.
+            """,
+        ),
         "out": attr.output(),
         "strict": attr.bool(
             default = False,
@@ -110,6 +118,7 @@ def bazelrc_preset(name, out_file = None, **kwargs):
             Label("//:strict.true"): True,
             "//conditions:default": False,
         })),
+        extra_presets = json.encode(kwargs.pop("extra_presets", {})),
         **kwargs
     )
     if not out_file:

tests/BUILD

@@ -1,5 +1,7 @@
+load("@aspect_bazel_lib//lib:testing.bzl", "assert_contains")
 load("@bazel_skylib//rules:native_binary.bzl", "native_test")
 load("//:bazelrc-preset.bzl", "bazelrc_preset")
+load(":extra_test_presets.bzl", "EXTRA_TEST_PRESETS")
 
 bazelrc_preset(
     name = "preset",
@@ -13,3 +15,29 @@ native_test(
     args = ["$(rootpath :preset)"],
     data = [":preset"],
 )
+
+bazelrc_preset(
+    name = "preset_with_extra_presets",
+    extra_presets = EXTRA_TEST_PRESETS | {
+        "extra_preset_as_dict": {
+            "command": "common:bar",
+            "default": True,
+            "description": """\
+            Extra preset that can be provided by the user.
+            """,
+        },
+    },
+    tags = ["manual"],
+)
+
+assert_contains(
+    name = "test_with_extra_presets_as_struct",
+    actual = ":preset_with_extra_presets",
+    expected = "common:foo --extra_preset_as_struct",
+)
+
+assert_contains(
+    name = "test_with_extra_presets_as_dict",
+    actual = ":preset_with_extra_presets",
+    expected = "common:bar --extra_preset_as_dict",
+)

tests/extra_test_presets.bzl

@@ -0,0 +1,12 @@
+"""Extra test presets for bazelrc-preset"""
+
+EXTRA_TEST_PRESETS = {
+    "extra_preset_as_struct": struct(
+        command = "common:foo",
+        default = True,
+        description = """\
+        Extra preset that can be provided by the user.
+        For instance to predefine https://github.com/aspect-build/toolchains_protoc?tab=readme-ov-file#ensure-protobuf-and-grpc-never-built.
+        """,
+    ),
+}