remote-execution-endpoint: fall back to remote-serve-endpoint

If only the `--remote-serve-endpoint` option is specified on the
command line, the `--remote-execution-endpoint` is also set to the
given value.

This makes the spawning and usage of just-execute consistent. When
just-serve is started, if no remote execution endpoint is provided,
the same process will also act as a just-execute instance. With the
current patch, the client can thus only write, on command line, the
remote serve address, avoiding the repetition of the same address for
two different options.

3 files changed, 27 insertions, 5 deletions

diff --git a/src/buildtool/main/main.cpp b/src/buildtool/main/main.cpp
index d6b06471..25458ef4 100644
--- a/src/buildtool/main/main.cpp
+++ b/src/buildtool/main/main.cpp
@@ -135,17 +135,32 @@ void SetupExecutionConfig(EndpointArguments const& eargs,
 }
 
 void SetupServeConfig(ServeArguments const& srvargs) {
-    using RemoteConfig = RemoteServeConfig;
     if (srvargs.remote_serve_address) {
-        if (not RemoteConfig::SetRemoteAddress(*srvargs.remote_serve_address)) {
+        if (not RemoteServeConfig::SetRemoteAddress(
+                *srvargs.remote_serve_address)) {
             Logger::Log(LogLevel::Error,
                         "setting serve service address '{}' failed.",
                         *srvargs.remote_serve_address);
             std::exit(kExitFailure);
         }
+        // if the user has not provided the --remote-execution-address, we fall
+        // back to the --remote-serve-address
+        if (auto client_remote_address = RemoteExecutionConfig::RemoteAddress();
+            !client_remote_address) {
+            if (!RemoteExecutionConfig::SetRemoteAddress(
+                    *srvargs.remote_serve_address)) {
+                Logger::Log(LogLevel::Error,
+                            "setting remote execution address '{}' failed.",
+                            *srvargs.remote_serve_address);
+                std::exit(kExitFailure);
+            }
+            Logger::Log(LogLevel::Info,
+                        "Using '{}' as the remote execution endpoint.",
+                        *srvargs.remote_serve_address);
+        }
     }
     if (not srvargs.repositories.empty() and
-        not RemoteConfig::SetKnownRepositories(srvargs.repositories)) {
+        not RemoteServeConfig::SetKnownRepositories(srvargs.repositories)) {
         Logger::Log(LogLevel::Error,
                     "setting serve service repositories failed.");
         std::exit(kExitFailure);
diff --git a/src/buildtool/serve_api/remote/configuration_client.cpp b/src/buildtool/serve_api/remote/configuration_client.cpp
index 25c38d79..f0615951 100644
--- a/src/buildtool/serve_api/remote/configuration_client.cpp
+++ b/src/buildtool/serve_api/remote/configuration_client.cpp
@@ -22,8 +22,8 @@ auto ConfigurationClient::CheckServeRemoteExecution() -> bool {
     auto client_remote_address = RemoteExecutionConfig::RemoteAddress();
     if (!client_remote_address) {
         logger_.Emit(LogLevel::Error,
-                     "In order to use just-serve, also the "
-                     "--remote-execution-address option must be given.");
+                     "Internal error: the remote execution endpoint should "
+                     "have been set.");
         return false;
     }
 
diff --git a/test/end-to-end/serve-service/serve_start_execute.sh b/test/end-to-end/serve-service/serve_start_execute.sh
index 6cc0448f..5cad0400 100644
--- a/test/end-to-end/serve-service/serve_start_execute.sh
+++ b/test/end-to-end/serve-service/serve_start_execute.sh
@@ -77,3 +77,10 @@ ENDTARGETS
 
 "${JUST}" install --local-build-root "${LBR}" -r localhost:${PORT} -o .
 grep 'just-serve-just-execute' out.txt
+
+# test that if we only pass --remote-serve-address it is also used as remote
+# execution endpoint
+
+rm -rf "${LBR}"
+"${JUST}" install --local-build-root "${LBR}" --remote-serve-address localhost:${PORT} -o .
+grep 'just-serve-just-execute' out.txt