Reject Dokka aggregate root path collisions

README.md

@@ -159,8 +159,8 @@ Both module attributes are optional. `module_name` defaults to the target name.
 `module_path` defaults to the target's full Bazel package path, preserving
 nested project structure; a target in the root package falls back to its target
 name. Use either attribute to override its derived value. Module paths must be
-portable relative paths and unique within an aggregate. Only HTML `dokka`
-targets can be aggregated.
+portable relative paths, unique within an aggregate, and must not collide with
+Dokka's root assets or index files. Only HTML `dokka` targets can be aggregated.
 
 The aggregate rule uses the same precedence and consumes the selected
 configuration's `offline_mode`, `plugins`, and `plugins_configuration` settings.

dokka/private/multi_module.bzl

@@ -3,6 +3,15 @@
 load(":providers.bzl", "DokkaConfigInfo", "DokkaInfo")
 
 _DOKKA_TOOLCHAIN_TYPE = Label("//dokka:toolchain_type")
+_DOKKA_RESERVED_ROOT_ENTRIES = [
+    "images",
+    "index.html",
+    "navigation.html",
+    "package-list",
+    "scripts",
+    "styles",
+    "ui-kit",
+]
 _WINDOWS_INVALID_PATH_CHARACTERS = ["<", ">", ":", "\"", "|", "?", "*"]
 
 def _validate_module_path(module_path, label):
@@ -27,6 +36,15 @@ def _validate_module_path(module_path, label):
             ).format(label, module_path),
         )
 
+    root_entry = segments[0].lower()
+    if root_entry in _DOKKA_RESERVED_ROOT_ENTRIES:
+        fail(
+            (
+                "Dokka target {} has invalid module_path '{}': first segment '{}' is reserved " +
+                "by Dokka's aggregate output."
+            ).format(label, module_path, segments[0]),
+        )
+
 def _dokka_multi_module_impl(ctx):
     modules = []
     module_paths = {}

tests/rules/BUILD.bazel

@@ -108,6 +108,13 @@ dokka(
     tags = ["manual"],
 )
 
+dokka(
+    name = "reserved_module_path_fixture",
+    srcs = ["Fixture.kt"],
+    module_path = "scripts/api",
+    tags = ["manual"],
+)
+
 dokka_multi_module(
     name = "multi_module_fixture",
     config = ":shared_config",
@@ -135,6 +142,12 @@ dokka_multi_module(
     tags = ["manual"],
 )
 
+dokka_multi_module(
+    name = "reserved_path_aggregate_fixture",
+    modules = [":reserved_module_path_fixture"],
+    tags = ["manual"],
+)
+
 dokka_multi_module(
     name = "non_html_aggregate_fixture",
     modules = [":analysis_fixture"],

tests/rules/dokka_analysis_test.bzl

@@ -384,6 +384,11 @@ def _invalid_module_path_test_impl(ctx):
     asserts.expect_failure(env, "has invalid module_path '../invalid'")
     return analysistest.end(env)
 
+def _reserved_module_path_test_impl(ctx):
+    env = analysistest.begin(ctx)
+    asserts.expect_failure(env, "first segment 'scripts' is reserved")
+    return analysistest.end(env)
+
 def _non_html_module_test_impl(ctx):
     env = analysistest.begin(ctx)
     asserts.expect_failure(env, "only accepts HTML `dokka` targets")
@@ -405,6 +410,10 @@ _invalid_module_path_test = analysistest.make(
     _invalid_module_path_test_impl,
     expect_failure = True,
 )
+_reserved_module_path_test = analysistest.make(
+    _reserved_module_path_test_impl,
+    expect_failure = True,
+)
 _non_html_module_test = analysistest.make(
     _non_html_module_test_impl,
     expect_failure = True,
@@ -444,6 +453,10 @@ def dokka_analysis_test_suite(name):
         name = name + "_invalid_module_path",
         target_under_test = ":invalid_path_aggregate_fixture",
     )
+    _reserved_module_path_test(
+        name = name + "_reserved_module_path",
+        target_under_test = ":reserved_path_aggregate_fixture",
+    )
     _non_html_module_test(
         name = name + "_non_html_module",
         target_under_test = ":non_html_aggregate_fixture",
@@ -458,6 +471,7 @@ def dokka_analysis_test_suite(name):
             ":" + name + "_invalid_module_path",
             ":" + name + "_multi_module",
             ":" + name + "_non_html_module",
+            ":" + name + "_reserved_module_path",
             ":" + name + "_reusable_config",
         ],
     )