Allow renaming generated Prost crate name (#3438)

## What?
Adds `crate_name` to `rust_prost_transform` which allows overriding the
generated crate name

## Why?
This allows the end user to control the name of the generated crates to
avoid conflicts.

Closes Prost Crate Naming Conventions #2889

Author: purkhusid

extensions/prost/private/prost.bzl

@@ -278,10 +278,18 @@ def _rust_prost_aspect_impl(target, ctx):
             transform_infos.append(data_target[ProstTransformInfo])
 
     rust_deps = runtime_deps + direct_deps
+    crate_name_overrides = []
     for transform_info in transform_infos:
         rust_deps.extend(transform_info.deps)
+        if transform_info.crate_name:
+            crate_name_overrides.append(transform_info.crate_name)
 
-    crate_name = ctx.label.name.replace("-", "_").replace("/", "_")
+    if len(crate_name_overrides) > 1:
+        fail("Multiple crate name overrides detected. Only one override is allowed. Please check your rust_prost_transform targets.")
+    elif len(crate_name_overrides) == 1:
+        crate_name = crate_name_overrides[0]
+    else:
+        crate_name = ctx.label.name.replace("-", "_").replace("/", "_")
 
     proto_info = target[ProtoInfo]
 

extensions/prost/private/prost_transform.bzl

@@ -6,6 +6,7 @@ load("@rules_rust//rust:defs.bzl", "rust_common")
 ProstTransformInfo = provider(
     doc = "Info about transformations to apply to Prost generated source code.",
     fields = {
+        "crate_name": "str: The name of crate generated by Prost.",
         "deps": "List[DepVariantInfo]: Additional dependencies to compile into the Prost target.",
         "prost_opts": "List[str]: Additional prost flags.",
         "srcs": "Depset[File]: Additional source files to include in generated Prost source code.",
@@ -27,6 +28,7 @@ def _rust_prost_transform_impl(ctx):
     # consumers of the `proto_library` target this rule is expected to be passed
     # to.
     return [ProstTransformInfo(
+        crate_name = ctx.attr.crate_name if ctx.attr.crate_name else None,
         deps = deps,
         prost_opts = ctx.attr.prost_opts,
         srcs = depset(ctx.files.srcs),
@@ -71,6 +73,10 @@ actions with minimal impact to other consumers.
 """,
     implementation = _rust_prost_transform_impl,
     attrs = {
+        "crate_name": attr.string(
+            doc = "The name of the crate generated by Prost. This is used to override the default name which is the name of the proto_library target.",
+            mandatory = False,
+        ),
         "deps": attr.label_list(
             doc = "Additional dependencies to add to the compiled crate.",
             providers = [[rust_common.crate_info], [rust_common.crate_group_info]],

extensions/prost/private/tests/same_proto_name/package1/BUILD.bazel

@@ -0,0 +1,29 @@
+load("@rules_proto//proto:defs.bzl", "proto_library")
+load("//:defs.bzl", "rust_prost_library", "rust_prost_transform")
+
+package(default_visibility = ["//private/tests:__subpackages__"])
+
+proto_library(
+    name = "models",
+    srcs = [
+        "models.proto",
+    ],
+    data = [
+        ":models_transform",
+    ],
+    strip_import_prefix = "/private/tests/same_proto_name",
+    deps = [
+        "//private/tests/same_proto_name/package2:models",
+        "//private/tests/same_proto_name/package3:models",
+    ],
+)
+
+rust_prost_transform(
+    name = "models_transform",
+    crate_name = "package1_models",
+)
+
+rust_prost_library(
+    name = "models_rs_proto",
+    proto = ":models",
+)

extensions/prost/private/tests/same_proto_name/package1/models.proto

@@ -0,0 +1,9 @@
+syntax = "proto3";
+
+package package1;
+import "package2/models.proto";
+import "package3/models.proto";
+
+message Model {
+    package2.Model model = 1;
+}

extensions/prost/private/tests/same_proto_name/package2/BUILD.bazel

@@ -0,0 +1,28 @@
+load("@rules_proto//proto:defs.bzl", "proto_library")
+load("//:defs.bzl", "rust_prost_library", "rust_prost_transform")
+
+package(default_visibility = ["//private/tests:__subpackages__"])
+
+proto_library(
+    name = "models",
+    srcs = [
+        "models.proto",
+    ],
+    data = [
+        ":models_transform",
+    ],
+    strip_import_prefix = "/private/tests/same_proto_name",
+    deps = [
+        "//private/tests/same_proto_name/package3:models",
+    ],
+)
+
+rust_prost_transform(
+    name = "models_transform",
+    crate_name = "package2_models",
+)
+
+rust_prost_library(
+    name = "models_rs_proto",
+    proto = ":models",
+)

extensions/prost/private/tests/same_proto_name/package2/models.proto

@@ -0,0 +1,8 @@
+syntax = "proto3";
+
+package package2;
+import "package3/models.proto";
+
+message Model {
+    package3.Model model = 1;
+}

extensions/prost/private/tests/same_proto_name/package3/BUILD.bazel

@@ -0,0 +1,25 @@
+load("@rules_proto//proto:defs.bzl", "proto_library")
+load("//:defs.bzl", "rust_prost_library", "rust_prost_transform")
+
+package(default_visibility = ["//private/tests:__subpackages__"])
+
+proto_library(
+    name = "models",
+    srcs = [
+        "models.proto",
+    ],
+    data = [
+        ":models_transform",
+    ],
+    strip_import_prefix = "/private/tests/same_proto_name",
+)
+
+rust_prost_transform(
+    name = "models_transform",
+    crate_name = "package3_models",
+)
+
+rust_prost_library(
+    name = "models_rs_proto",
+    proto = ":models",
+)

extensions/prost/private/tests/same_proto_name/package3/models.proto

@@ -0,0 +1,7 @@
+syntax = "proto3";
+
+package package3;
+
+message Model {
+    string stuff = 1;
+}