Add kt_jvm_proto_helper as individual rule. (#396)

* Add kt_jvm_proto_helper as individual rule.

This allows the BUILD file to have separate java proto and kt proto
rules in case there is a mix of java and proto projects in the same
repo, and there are stricter requirement to the output (e.g. leaner
dependency chains, smaller binaries for pure-java outputs etc.).

This also bypasses an issue in the other rules where the
kt_jvm_*_library would compile the whole dependency chain to kotlin, and
if the bazel repo is large with many proto dependencies, an can easily
end up caching all of these when containing the same classes. If only
some of these are refreshed / synced on changes you can easily end up
with an IDE claiming your new fields still dont' exist, or removed
classes are still there etc.

* Also make rule for gRPC part.

Which makes btth kr_proto and kt_grpc helper functions.

* Alternate approach to support java targets

* Fix error introduced during merge

---------

Co-authored-by: James Ward <james@jamesward.com>
Co-authored-by: aragos <aragos@gmail.com>

kt_jvm_grpc.bzl

@@ -160,6 +160,74 @@ def kt_jvm_grpc_library(
         features = features,
     )
 
+def kt_jvm_grpc_no_java_library(
+        name,
+        srcs = None,
+        deps = None,
+        java_grpc_dep = None,
+        tags = None,
+        testonly = None,  # None to not override Bazel's default
+        compatible_with = None,
+        restricted_to = None,
+        visibility = None,
+        deprecation = None,
+        features = []):
+    """This rule compiles Kotlin APIs for gRPC services from the proto_library in srcs.
+
+    Unlike kt_jvm_grpc_library, this rule will not generate a java_grpc_library target
+    implicitly but instead expects one as an input to java_grpc_dep.
+
+    For standard attributes, see:
+      https://docs.bazel.build/versions/master/be/common-definitions.html#common-attributes
+
+    Args:
+      name: A name for the target
+      srcs: Exactly one proto_library target to generate Kotlin APIs for
+      deps: Exactly one java_proto_library target for srcs[0]
+      java_grpc_dep: java_grpc_library target for the java_proto_library in deps
+      tags: A list of string tags passed to generated targets.
+      testonly: Whether this target is intended only for tests.
+      compatible_with: Standard attribute
+      restricted_to: Standard attribute
+      visibility: A list of targets allowed to depend on this rule.
+      deprecation: Standard attribute
+      features: Features enabled.
+    """
+    srcs = srcs or []
+    deps = deps or []
+
+    if len(srcs) != 1:
+        fail("Expected exactly one src", "srcs")
+    if len(deps) != 1:
+        fail("Expected exactly one dep", "deps")
+    if not java_grpc_dep:
+        fail("A java_grpc_dep is required", "java_grpc_dep")
+
+    kt_grpc_label = ":%s_DO_NOT_DEPEND_kt_grpc" % name
+    kt_grpc_name = kt_grpc_label[1:]
+
+    _kt_grpc_generate_code(
+        name = kt_grpc_name,
+        srcs = srcs,
+        deps = deps,
+    )
+
+    kt_jvm_library(
+        name = name,
+        srcs = [kt_grpc_label],
+        deps = [
+            java_grpc_dep,
+            "@com_github_grpc_grpc_kotlin//stub/src/main/java/io/grpc/kotlin:stub",
+            "@com_github_grpc_grpc_kotlin//stub/src/main/java/io/grpc/kotlin:context",
+        ],
+        compatible_with = compatible_with,
+        restricted_to = restricted_to,
+        testonly = testonly,
+        visibility = visibility,
+        deprecation = deprecation,
+        features = features,
+    )
+
 def _get_real_short_path(file):
     """Returns the correct short path file name to be used by protoc."""
     short_path = file.short_path
@@ -200,7 +268,6 @@ def _kt_jvm_proto_library_helper_impl(ctx):
         outputs = [gen_src_dir],
         executable = ctx.executable._protoc,
         arguments = [protoc_args],
-        mnemonic = "KtProtoGenerator",
         progress_message = "Generating kotlin proto extensions for " +
                            ", ".join([
                                str(dep.label)
@@ -252,6 +319,7 @@ _kt_jvm_proto_library_helper = rule(
 def kt_jvm_proto_library(
         name,
         deps = None,
+        java_deps = None,
         tags = None,
         testonly = None,
         compatible_with = None,
@@ -267,15 +335,17 @@ def kt_jvm_proto_library(
     See also https://developers.google.com/protocol-buffers/docs/kotlintutorial for how to interact
     with the generated Kotlin representation.
 
-    Note that the rule will also export the java version of the same protos as Kotlin protos depend
-    on the java version under the hood.
+    If "java_deps" are set, they must be exactly the java_proto_library targets for "deps". If
+    "java_deps" are not set, this rule will generate and export the java protos for all "deps",
+    using "flavor" to determine their type.
 
     For standard attributes, see:
       https://docs.bazel.build/versions/master/be/common-definitions.html#common-attributes
 
     Args:
       name: A name for the target
       deps: One or more proto_library targets to turn into Kotlin.
+      java_deps: (optional) java_proto_library targets corresponding to deps
       tags: Standard attribute
       testonly: Standard attribute
       compatible_with: Standard attribute
@@ -286,40 +356,43 @@ def kt_jvm_proto_library(
       deprecation: Standard attribute
       features: Standard attribute
     """
-    java_proto_target = ":%s_DO_NOT_DEPEND_java_proto" % name
-    helper_target = ":%s_DO_NOT_DEPEND_kt_proto" % name
-
-    if flavor == "lite":
-        native.java_lite_proto_library(
-            name = java_proto_target[1:],
-            deps = deps,
-            testonly = testonly,
-            compatible_with = compatible_with,
-            visibility = ["//visibility:private"],
-            restricted_to = restricted_to,
-            tags = tags,
-            deprecation = deprecation,
-            features = features,
-        )
+    if (java_deps != None and len(java_deps) > 0):
+        java_protos = java_deps
+        java_exports = []
     else:
-        native.java_proto_library(
-            name = java_proto_target[1:],
-            deps = deps,
-            testonly = testonly,
-            compatible_with = compatible_with,
-            visibility = ["//visibility:private"],
-            restricted_to = restricted_to,
-            tags = tags,
-            deprecation = deprecation,
-            features = features,
-        )
+        java_proto_target = ":%s_DO_NOT_DEPEND_java_proto" % name
+        if flavor == "lite":
+            native.java_lite_proto_library(
+                name = java_proto_target[1:],
+                deps = deps,
+                testonly = testonly,
+                compatible_with = compatible_with,
+                visibility = ["//visibility:private"],
+                restricted_to = restricted_to,
+                tags = tags,
+                deprecation = deprecation,
+                features = features,
+            )
+        else:
+            native.java_proto_library(
+                name = java_proto_target[1:],
+                deps = deps,
+                testonly = testonly,
+                compatible_with = compatible_with,
+                visibility = ["//visibility:private"],
+                restricted_to = restricted_to,
+                tags = tags,
+                deprecation = deprecation,
+                features = features,
+            )
+        java_protos = [java_proto_target]
+        java_exports = [java_proto_target]
 
+    helper_target = ":%s_DO_NOT_DEPEND_kt_proto" % name
     _kt_jvm_proto_library_helper(
         name = helper_target[1:],
         proto_deps = deps,
-        deps = [
-            java_proto_target,
-        ],
+        deps = java_protos,
         testonly = testonly,
         compatible_with = compatible_with,
         visibility = ["//visibility:private"],
@@ -334,11 +407,8 @@ def kt_jvm_proto_library(
         srcs = [helper_target + ".srcjar"],
         deps = [
             "@maven//:com_google_protobuf_protobuf_kotlin",
-            java_proto_target,
-        ],
-        exports = [
-            java_proto_target,
-        ],
+        ] + java_protos,
+        exports = java_exports,
         testonly = testonly,
         compatible_with = compatible_with,
         visibility = visibility,