gRPC import scan is not picking up dependencies

[fatihcatalkaya]

Describe the bug

I would like to use the google.type.Decimal and google.rpc.Status message types within my message. Therefore, I have com.google.api.grpc:proto-google-common-protos:2.61.1 dependency in my project, as this dependency contains these grpc message definitions. In the gRPC code generation guide in the section "Proto files from dependencies" it says, that I need to put in the following line into my application.properties file, so that Quarkus is able to pick up the dependency:

quarkus.generate-code.grpc.scan-for-imports=com.google.api.grpc:proto-google-common-protos

However, when I run ./mvnw quarkus:generate-code, the compilation fails, because of missing type definition for the messages "Decimal" and "Status".

Expected behavior

The invocation of the gRPC protoc compiler finishes successfully.

Actual behavior

The invocation of the gRPC protoc compiler fails with the message:

[INFO] Scanning for projects...
[INFO] 
[INFO] ----------------------< dev.catalkaya:grpc-test >-----------------------
[INFO] Building grpc-test 1.0-SNAPSHOT
[INFO]   from pom.xml
[INFO] --------------------------------[ jar ]---------------------------------
[INFO] 
[INFO] --- quarkus:3.28.2:generate-code (default-cli) @ grpc-test ---
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  1.131 s
[INFO] Finished at: 2025-10-02T09:38:34+02:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal io.quarkus.platform:quarkus-maven-plugin:3.28.2:generate-code (default-cli) on project grpc-test: Quarkus code generation phase has failed: InvocationTargetException: Failed to generate Java classes from proto files: [/home/user/IdeaProjects/grpc-test/src/main/proto/my_message.proto] to /home/user/IdeaProjects/grpc-test/target/generated-sources/grpc with command /home/user/IdeaProjects/grpc-test/target/com.google.protobuf-protoc-linux-x86_64-exe -I=/home/user/IdeaProjects/grpc-test/src/main/proto -I=/home/user/IdeaProjects/grpc-test/target/protoc-dependencies/887869d68b3d4324376eb9ee6db4956483e8eaf8 --plugin=protoc-gen-grpc=/home/user/IdeaProjects/grpc-test/target/io.grpc-protoc-gen-grpc-java-linux-x86_64-exe --plugin=protoc-gen-q-grpc=/home/user/IdeaProjects/grpc-test/target/quarkus-grpc3713215682483653349.sh --q-grpc_out=/home/user/IdeaProjects/grpc-test/target/generated-sources/grpc --grpc_out=/home/user/IdeaProjects/grpc-test/target/generated-sources/grpc --java_out=/home/user/IdeaProjects/grpc-test/target/generated-sources/grpc /home/user/IdeaProjects/grpc-test/src/main/proto/my_message.proto: Process exited abnormally (pid 30270) with exit code 1 with error output:
[ERROR]  > google/type/decimal.proto: File not found.
[ERROR]  > my_message.proto:5:1: Import "google/type/decimal.proto" was not found or had errors.
[ERROR]  > my_message.proto:12:3: "google.type.Decimal" is not defined.
[ERROR] -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException

How to Reproduce?

I have created a dedicated GitHub repository to reproduce the error here: https://github.com/fatihcatalkaya/congenial-telegram

In the reproducer I have

• defined a message "MyMessage" which includes the "google.type.Decimal" type
• I have included the com.google.api.grpc:proto-google-common-protos in the pom.xml
• Added quarkus.generate-code.grpc.scan-for-imports=com.google.api.grpc:proto-google-common-protos to the application.properties
• Run ./mvnw quarkus:generate-code expecting it to build successfully (but fails)

Output of uname -a or ver

Linux MyDesktop 6.8.0-84-generic #84-Ubuntu SMP PREEMPT_DYNAMIC Fri Sep 5 22:36:38 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux

Output of java -version

openjdk version "21.0.8" 2025-07-15 OpenJDK Runtime Environment (build 21.0.8+9-Ubuntu-0ubuntu124.04.1) OpenJDK 64-Bit Server VM (build 21.0.8+9-Ubuntu-0ubuntu124.04.1, mixed mode, sharing)

Quarkus version or git rev

3.28.2

Build tool (ie. output of mvnw --version or gradlew --version)

Maven 3.9.11

Additional information

No response

[quarkus-bot]

/cc @alesj (grpc), @cescoffier (grpc)

[cescoffier]

Do you have the protoc command line that would compile your protos?

[fatihcatalkaya]

@cescoffier Not at hand, I'll try to provide one. It's also the first time that I am dealing with gRPC, I must admit 😅

I've looked a little bit closer into the compiler command that gets invoked, which is this one:

/home/fatih/IdeaProjects/grpc-test/target/com.google.protobuf-protoc-linux-x86_64-exe -I = /home/fatih/IdeaProjects/grpc-test/src/main/proto
-I = /home/fatih/IdeaProjects/grpc-test/target/protoc-dependencies/887869d68b3d4324376eb9ee6db4956483e8eaf8
--plugin = protoc-gen-grpc= /home/fatih/IdeaProjects/grpc-test/target/io.grpc-protoc-gen-grpc-java-linux-x86_64-exe
--plugin = protoc-gen-q-grpc= /home/fatih/IdeaProjects/grpc-test/target/quarkus-grpc12126182670880980580.sh
--q-grpc_out = /home/fatih/IdeaProjects/grpc-test/target/generated-sources/grpc
--grpc_out = /home/fatih/IdeaProjects/grpc-test/target/generated-sources/grpc
--java_out = /home/fatih/IdeaProjects/grpc-test/target/generated-sources/grpc /home/fatih/IdeaProjects/grpc-test/src/main/proto/my_message.proto

I also noticed, that the /home/fatih/IdeaProjects/grpc-test/target/protoc-dependencies/887869d68b3d4324376eb9ee6db4956483e8eaf8 directory contains the common grpc types:

> tree target/protoc-dependencies/887869d68b3d4324376eb9ee6db4956483e8eaf8
target/protoc-dependencies/887869d68b3d4324376eb9ee6db4956483e8eaf8
└── google
    └── protobuf
        ├── any.proto
        ├── api.proto
        ├── descriptor.proto
        ├── duration.proto
        ├── empty.proto
        ├── field_mask.proto
        ├── source_context.proto
        ├── struct.proto
        ├── timestamp.proto
        ├── type.proto
        └── wrappers.proto

3 directories, 11 files

So currently, I can not see where the compilation command references any of the com.google.api.grpc:proto-google-common-protos dependencies, which I configured for a scan.

[fatihcatalkaya]

@cescoffier So I managed to compile my protocol buffers. For the manual compilation to work I performed the following steps:

1. Extract the com.google.api.grpc:proto-google-common-protos jar file into target/protoc-dependencies
2. Include -I=/home/fatih/IdeaProjects/grpc-test/target/protoc-dependencies/proto-google-common-protos in compilation command.

The full command looks like this:

/home/fatih/IdeaProjects/grpc-test/target/com.google.protobuf-protoc-linux-x86_64-exe \
  -I=/home/fatih/IdeaProjects/grpc-test/src/main/proto \
  -I=/home/fatih/IdeaProjects/grpc-test/target/protoc-dependencies/887869d68b3d4324376eb9ee6db4956483e8eaf8 \
  -I=/home/fatih/IdeaProjects/grpc-test/target/protoc-dependencies/proto-google-common-protos  \
  --plugin=protoc-gen-grpc=/home/fatih/IdeaProjects/grpc-test/target/io.grpc-protoc-gen-grpc-java-linux-x86_64-exe \
  --plugin=protoc-gen-q-grpc=/home/fatih/IdeaProjects/grpc-test/target/quarkus-grpc3647687870778133554.sh \
  --q-grpc_out=/home/fatih/IdeaProjects/grpc-test/target/generated-sources/grpc \
  --grpc_out=/home/fatih/IdeaProjects/grpc-test/target/generated-sources/grpc \
  --java_out=/home/fatih/IdeaProjects/grpc-test/target/generated-sources/grpc /home/fatih/IdeaProjects/grpc-test/src/main/proto/my_message.proto

[fatihcatalkaya]

@cescoffier were you able to reproduce the issue using the reproducer?

[cescoffier]

Unfortunately, I didn't have the time to loo0k at it. I'm away this week - will try to have a look once back.