scala_doc: Add support for building docs without transitive dependencies (#1331)

* scala_doc: Add support for building docs without transitive dependencies

* Apply lint fixes

* scala-doc: Use aspect instead of a flag to build docs without transitive dependencies

* Address nits

* scala_doc: Add comment to explain why we are exporting make_scala_doc_rule

* scala_doc: Lint fixes

* scala_doc: Use exec instead of host

Author: rahuliyer95

scala/private/rules/scala_doc.bzl

@@ -8,16 +8,26 @@ _ScaladocAspectInfo = provider(fields = [
     "plugins",
 ])
 
-def _scaladoc_aspect_impl(target, ctx):
+def _scaladoc_intransitive_aspect_impl(target, ctx):
+    """Build scaladocs only for the provided targets."""
+    return _scaladoc_aspect_impl(target, ctx, transitive = False)
+
+def _scaladoc_aspect_impl(target, ctx, transitive = True):
     """Collect source files and compile_jars from JavaInfo-returning deps."""
 
     # We really only care about visited targets with srcs, so only look at those.
     if hasattr(ctx.rule.attr, "srcs"):
         # Collect only Java and Scala sources enumerated in visited targets, including src_files in deps.
-        src_files = depset(
-            direct = [file for file in ctx.rule.files.srcs if file.extension.lower() in ["java", "scala"]],
-            transitive = [dep[_ScaladocAspectInfo].src_files for dep in ctx.rule.attr.deps if _ScaladocAspectInfo in dep],
-        )
+        direct_deps = [file for file in ctx.rule.files.srcs if file.extension.lower() in ["java", "scala"]]
+
+        # Sometimes we only want to generate scaladocs for a single target and not all of its
+        # dependencies
+        if transitive:
+            transitive_deps = [dep[_ScaladocAspectInfo].src_files for dep in ctx.rule.attr.deps if _ScaladocAspectInfo in dep]
+        else:
+            transitive_deps = []
+
+        src_files = depset(direct = direct_deps, transitive = transitive_deps)
 
         # Collect compile_jars from visited targets' deps.
         compile_jars = depset(
@@ -40,14 +50,22 @@ def _scaladoc_aspect_impl(target, ctx):
     else:
         return []
 
-_scaladoc_aspect = aspect(
+_scaladoc_transitive_aspect = aspect(
     implementation = _scaladoc_aspect_impl,
     attr_aspects = ["deps"],
     required_aspect_providers = [
         [JavaInfo],
     ],
 )
 
+scaladoc_intransitive_aspect = aspect(
+    implementation = _scaladoc_intransitive_aspect_impl,
+    attr_aspects = ["deps"],
+    required_aspect_providers = [
+        [JavaInfo],
+    ],
+)
+
 def _scala_doc_impl(ctx):
     # scaladoc warns if you don't have the output directory already created, which is annoying.
     output_path = ctx.actions.declare_directory("{}.html".format(ctx.attr.name))
@@ -85,19 +103,20 @@ def _scala_doc_impl(ctx):
 
     return [DefaultInfo(files = depset(direct = [output_path]))]
 
-scala_doc = rule(
-    attrs = {
-        "deps": attr.label_list(
-            aspects = [_scaladoc_aspect],
-            providers = [JavaInfo],
-        ),
-        "scalacopts": attr.string_list(),
-        "_scaladoc": attr.label(
-            cfg = "host",
-            executable = True,
-            default = Label("//src/scala/io/bazel/rules_scala/scaladoc_support:scaladoc_generator"),
-        ),
-    },
-    doc = "Generate Scaladoc HTML documentation for source files in from the given dependencies.",
-    implementation = _scala_doc_impl,
-)
+def make_scala_doc_rule(aspect = _scaladoc_transitive_aspect):
+    return rule(
+        attrs = {
+            "deps": attr.label_list(
+                aspects = [aspect],
+                providers = [JavaInfo],
+            ),
+            "scalacopts": attr.string_list(),
+            "_scaladoc": attr.label(
+                cfg = "exec",
+                executable = True,
+                default = Label("//src/scala/io/bazel/rules_scala/scaladoc_support:scaladoc_generator"),
+            ),
+        },
+        doc = "Generate Scaladoc HTML documentation for source files in from the given dependencies.",
+        implementation = _scala_doc_impl,
+    )

scala/scala.bzl

@@ -12,7 +12,8 @@ load(
 )
 load(
     "@io_bazel_rules_scala//scala/private:rules/scala_doc.bzl",
-    _scala_doc = "scala_doc",
+    _make_scala_doc_rule = "make_scala_doc_rule",
+    _scaladoc_intransitive_aspect = "scaladoc_intransitive_aspect",
 )
 load(
     "@io_bazel_rules_scala//scala/private:rules/scala_junit_test.bzl",
@@ -50,7 +51,11 @@ def scala_specs2_junit_test(name, **kwargs):
 
 # Re-export private rules for public consumption
 scala_binary = _scala_binary
-scala_doc = _scala_doc
+
+# These are exported for enabling users to build scaladocs without transitive dependencies.
+make_scala_doc_rule = _make_scala_doc_rule
+scaladoc_intransitive_aspect = _scaladoc_intransitive_aspect
+scala_doc = _make_scala_doc_rule()
 scala_junit_test = _scala_junit_test
 scala_library = _scala_library
 scala_library_for_plugin_bootstrapping = _scala_library_for_plugin_bootstrapping