feat(conflict): Add a fake Tango server that reads targets from a git repository

Makefile

@@ -154,7 +154,7 @@ define assert_clean
 	fi
 endef
 
-.PHONY: build build-all-linux build-runway-linux build-submitqueue-gateway-client build-submitqueue-gateway-linux build-submitqueue-gateway-server build-submitqueue-orchestrator-linux build-stovepipe-linux build-stovepipe-linux-debug check-gazelle check-mocks check-tidy clean clean-proto demo-requests deps docs-build docs-serve e2e-test fmt gazelle integration-test integration-test-submitqueue-consumer integration-test-extensions integration-test-submitqueue-gateway integration-test-submitqueue-orchestrator integration-test-submitqueue-validator license-fix lint lint-binary lint-fmt lint-license local-init-runway-queue-schema local-init-stovepipe-schemas local-runway-start local-runway-stop local-submitqueue-stop local-submitqueue-clean local-submitqueue-gateway-start local-submitqueue-gateway-stop local-init-submitqueue-schemas local-submitqueue-logs local-submitqueue-orchestrator-start local-submitqueue-orchestrator-stop local-submitqueue-ps local-submitqueue-restart local-submitqueue-start local-stop local-stovepipe-debug-start local-stovepipe-logs local-stovepipe-start local-stovepipe-stop mocks proto query-deps query-targets run-client-runway run-client-submitqueue-gateway run-client-submitqueue-orchestrator run-client-stovepipe run-queue-admin test test-no-cache test-race tidy tidy-bazel tidy-go web-build web-check web-e2e-test web-image-load web-install web-proto help
+.PHONY: build build-all-linux build-runway-linux build-submitqueue-gateway-client build-submitqueue-gateway-linux build-submitqueue-gateway-server build-submitqueue-orchestrator-linux build-stovepipe-linux build-stovepipe-linux-debug build-tangofake-linux check-gazelle check-mocks check-tidy clean clean-proto demo-requests deps docs-build docs-serve e2e-test fmt gazelle integration-test integration-test-submitqueue-consumer integration-test-extensions integration-test-submitqueue-gateway integration-test-submitqueue-orchestrator integration-test-submitqueue-validator license-fix lint lint-binary lint-fmt lint-license local-init-runway-queue-schema local-init-stovepipe-schemas local-runway-start local-runway-stop local-submitqueue-stop local-submitqueue-clean local-submitqueue-gateway-start local-submitqueue-gateway-stop local-init-submitqueue-schemas local-submitqueue-logs local-submitqueue-orchestrator-start local-submitqueue-orchestrator-stop local-submitqueue-ps local-submitqueue-restart local-submitqueue-start local-stop local-stovepipe-debug-start local-stovepipe-logs local-stovepipe-start local-stovepipe-stop mocks proto query-deps query-targets run-client-runway run-client-submitqueue-gateway run-client-submitqueue-orchestrator run-client-stovepipe run-queue-admin test test-no-cache test-race tidy tidy-bazel tidy-go web-build web-check web-e2e-test web-image-load web-install web-proto help
 
 
 build: ## Build all services and examples
@@ -224,6 +224,14 @@ build-stovepipe-linux-debug: ## Build Stovepipe Linux debug binary for Docker/de
 	 cp -f bazel-bin/service/stovepipe/server/stovepipe .docker-bin/stovepipe-debug
 	@echo "Stovepipe Linux debug binary ready at .docker-bin/stovepipe-debug"
 
+build-tangofake-linux: ## Build the fake Tango server's Linux binary for Docker
+	@echo "Building the fake Tango server Linux binary for Docker..."
+	@$(BAZEL) build --platforms=@rules_go//go/toolchain:linux_amd64 //service/tangofake/server:server
+	@mkdir -p .docker-bin
+	@cp -f bazel-bin/service/tangofake/server/server_/server .docker-bin/tangofake 2>/dev/null || \
+	 cp -f bazel-bin/service/tangofake/server/server .docker-bin/tangofake
+	@echo "Fake Tango server Linux binary ready at .docker-bin/tangofake"
+
 check-gazelle: ## Check BUILD.bazel files are up to date
 	@echo "Running Gazelle to check BUILD files..."
 	@$(BAZEL) run //:gazelle

service/README.md

@@ -7,6 +7,7 @@ Each domain has its own subdirectory with a dedicated README:
 - [`submitqueue/`](submitqueue/README.md) — the multi-service SubmitQueue domain (Gateway + Orchestrator).
 - [`stovepipe/`](stovepipe/README.md) — the single-service Stovepipe domain (ingest → process → build → buildsignal → record).
 - [`runway/`](runway/README.md) — the single-service Runway merge execution service.
+- [`tangofake/`](tangofake/README.md) — a fake Tango server for running the Tango conflict analyzer without a build system.
 
 ## Services
 
@@ -16,6 +17,7 @@ Each domain has its own subdirectory with a dedicated README:
 | **SubmitQueue Orchestrator** | 8082 | `submitqueue` | `Ping` (+ consumes start, cancel, validate, merge-conflict-check-signal, batch, dependency-analysis, speculate, build, buildsignal, submitqueue-land, merge-signal, conclude, submitqueue-hook, and paired DLQ topics) | MySQL app + queue |
 | **Stovepipe** | 8083 | `stovepipe` | `Ping`, `Ingest` (+ consumes process, build, buildsignal, record, stovepipe-hook, and paired DLQ topics) | MySQL storage + queue |
 | **Runway** | 8086 | `runway` | `Ping` (+ consumes merge-conflict-check & runway-merge topics) | MySQL queue |
+| **Fake Tango** | free port, logged | none | Tango's `GetChangedTargets` | a git repository of `TARGET` files |
 
 Ports above are the `go run` defaults; under Docker Compose each server listens on `:8080` inside its container and is published on a random ephemeral host port. `make local-submitqueue-ps` is the only status target, and it prints the SubmitQueue mappings. `make local-stovepipe-start` and `make local-runway-start` print their ports when those stacks come up.
 
@@ -37,9 +39,11 @@ service/
 │   ├── docker-compose.debug.yml        # Debug variant with delve
 │   ├── server/                         # Stovepipe gRPC server + Dockerfile + compose
 │   └── client/                         # Stovepipe ping client
-└── runway/
-    ├── server/                         # Runway gRPC server + Dockerfile + compose
-    └── client/                         # Runway ping client
+├── runway/
+│   ├── server/                         # Runway gRPC server + Dockerfile + compose
+│   └── client/                         # Runway ping client
+└── tangofake/
+    └── server/                         # Fake Tango gRPC server + Dockerfile + compose
 ```
 
 ## Running

service/tangofake/BUILD.bazel

@@ -0,0 +1,37 @@
+load("@rules_go//go:def.bzl", "go_library", "go_test")
+
+go_library(
+    name = "go_default_library",
+    srcs = ["tangofake.go"],
+    importpath = "github.com/uber/submitqueue/service/tangofake",
+    visibility = [
+        "//service/tangofake:__subpackages__",
+        "//test:__subpackages__",
+    ],
+    deps = [
+        "//platform/extension/gitworkspace:go_default_library",
+        "@com_github_uber_tango//tangopb:go_default_library",
+    ],
+)
+
+go_test(
+    name = "go_default_test",
+    srcs = ["tangofake_test.go"],
+    # The pinned git, for building the repositories the tests read.
+    data = ["@git"],
+    embed = [":go_default_library"],
+    env = {
+        "SUBMITQUEUE_TEST_GIT": "$(location @git//:git)",
+    },
+    deps = [
+        "//platform/extension/gitworkspace/local:go_default_library",
+        "//platform/git/exectest:go_default_library",
+        "//submitqueue/extension/conflict/tango:go_default_library",
+        "//submitqueue/extension/conflict/tango/tangoclient:go_default_library",
+        "@com_github_stretchr_testify//assert:go_default_library",
+        "@com_github_stretchr_testify//require:go_default_library",
+        "@com_github_uber_tango//tangopb:go_default_library",
+        "@org_uber_go_yarpc//:go_default_library",
+        "@org_uber_go_yarpc//transport/grpc:go_default_library",
+    ],
+)

service/tangofake/README.md

@@ -0,0 +1,14 @@
+# Fake Tango server
+
+A runnable stand-in for a Tango server, for running the SubmitQueue Tango conflict analyzer without a build system. It serves Tango's real gRPC protocol and derives the changed targets from `TARGET` files in a git repository, so the analyzer exercises the same client path it uses against a real Tango. The target-file format and how a change maps to targets are described in the package doc of [`tangofake.go`](tangofake.go).
+
+## Running it
+
+It runs as a container like the other services here. Build the Linux binary with `make build-tangofake-linux`, then bring it up with [`server/docker-compose.yml`](server/docker-compose.yml), pointing `SQ_TANGOFAKE_REPO_DIR` at a git repository that holds the `TARGET` files. The server listens on port 8080 in the container.
+
+Outside a container, `bazel run //service/tangofake/server -- -repo <path>` serves the same repository on a free port, which it logs.
+
+## Flags
+
+- `-repo` is the path to the git repository holding the `TARGET` files. It is required, and the repository must contain every commit a change URI names.
+- `-address` is the gRPC listen address and defaults to `127.0.0.1:0`.

service/tangofake/server/BUILD.bazel

@@ -0,0 +1,21 @@
+load("@rules_go//go:def.bzl", "go_binary", "go_library")
+
+go_library(
+    name = "go_default_library",
+    srcs = ["main.go"],
+    importpath = "github.com/uber/submitqueue/service/tangofake/server",
+    visibility = ["//visibility:private"],
+    deps = [
+        "//platform/extension/gitworkspace/local:go_default_library",
+        "//service/tangofake:go_default_library",
+        "@com_github_uber_tango//tangopb:go_default_library",
+        "@org_uber_go_yarpc//:go_default_library",
+        "@org_uber_go_yarpc//transport/grpc:go_default_library",
+    ],
+)
+
+go_binary(
+    name = "server",
+    embed = [":go_default_library"],
+    visibility = ["//visibility:public"],
+)

service/tangofake/server/Dockerfile

@@ -0,0 +1,15 @@
+FROM debian:bookworm-slim
+
+# git is a runtime dependency: the fake reads targets out of a repository by
+# running it.
+RUN apt-get update && apt-get install -y ca-certificates git && rm -rf /var/lib/apt/lists/* \
+    && mkdir -p /app && chmod 0755 /app
+WORKDIR /app
+
+# Built via: make build-tangofake-linux
+COPY .docker-bin/tangofake ./tangofake
+RUN chmod 0555 ./tangofake
+
+EXPOSE 8080
+
+CMD ["/app/tangofake"]

service/tangofake/server/docker-compose.yml

@@ -0,0 +1,21 @@
+# Docker Compose for the fake Tango server on its own.
+#
+# IMPORTANT: Before running compose, build the Linux binary:
+#   make build-tangofake-linux
+#
+# Quick start, pointing it at a git repository that holds TARGET files:
+#   SQ_TANGOFAKE_REPO_DIR=/path/to/repo REPO_ROOT=$PWD \
+#     docker compose -f service/tangofake/server/docker-compose.yml up --build
+
+services:
+  tangofake-service:
+    image: ${SQ_DOCKER_IMAGE_PREFIX:-submitqueue}-tangofake-service:latest
+    build:
+      context: ${REPO_ROOT}
+      dockerfile: service/tangofake/server/Dockerfile
+    user: "${SQ_CONTAINER_USER:-0:0}"
+    command: ["/app/tangofake", "-repo", "/var/tangofake/repo", "-address", "0.0.0.0:8080"]
+    ports:
+      - "8080" # Random ephemeral port to avoid conflicts
+    volumes:
+      - ${SQ_TANGOFAKE_REPO_DIR:?set SQ_TANGOFAKE_REPO_DIR to the repository holding the TARGET files}:/var/tangofake/repo:ro

service/tangofake/server/main.go

@@ -0,0 +1,74 @@
+// Copyright (c) 2026 Uber Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Command server serves a Tango server over gRPC that derives changed
+// targets from the TARGET files of a git repository (see package tangofake),
+// for running the SubmitQueue demo without a build system.
+package main
+
+import (
+	"flag"
+	"fmt"
+	"log"
+	"net"
+	"os"
+	"os/signal"
+	"syscall"
+
+	"github.com/uber/tango/tangopb"
+	"go.uber.org/yarpc"
+	"go.uber.org/yarpc/transport/grpc"
+
+	"github.com/uber/submitqueue/platform/extension/gitworkspace/local"
+	"github.com/uber/submitqueue/service/tangofake"
+)
+
+func main() {
+	if err := run(); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func run() error {
+	repo := flag.String("repo", "", "path to the git repository holding the TARGET files")
+	address := flag.String("address", "127.0.0.1:0", "address to listen on for gRPC; port 0 picks a free port, which is logged")
+	flag.Parse()
+	if *repo == "" {
+		return fmt.Errorf("-repo is required")
+	}
+
+	listener, err := net.Listen("tcp", *address)
+	if err != nil {
+		return fmt.Errorf("failed to listen on %s: %w", *address, err)
+	}
+
+	transport := grpc.NewTransport()
+	dispatcher := yarpc.NewDispatcher(yarpc.Config{
+		Name:     "tango",
+		Inbounds: yarpc.Inbounds{transport.NewInbound(listener)},
+	})
+	dispatcher.Register(tangopb.BuildTangoYARPCProcedures(tangofake.New(tangofake.Params{
+		Workspaces: local.NewFactory(local.Params{Dir: *repo}),
+	})))
+	if err := dispatcher.Start(); err != nil {
+		return fmt.Errorf("failed to start the server: %w", err)
+	}
+	defer func() { _ = dispatcher.Stop() }()
+
+	log.Printf("fake tango serving %s on %s", *repo, listener.Addr())
+	stop := make(chan os.Signal, 1)
+	signal.Notify(stop, syscall.SIGINT, syscall.SIGTERM)
+	<-stop
+	return nil
+}