feature: navigate to Java files materialized from .proto files by damiankus-vl · Pull Request #8699 · scalameta/metals

damiankus-vl · 2026-07-20T14:24:41Z

Generate read-only Javas file from .proto files and materialize them under .metals/readonly, so go-to-definition on a proto-generated class (message, enum, gRPC stub) lands in the generated Java source alongside the .proto declaration. Route the materialized file to the proto's build target and feed the outlines through the turbine classpath so hover and completion resolve proto-generated types too.

DEMO

An example based on issue #8651 - https://github.com/buildfarm/buildfarm

go to persistentworkers/examples/src/test/java/adder/AdderTest.java
hover over waitAndRead in line 44
check the return type in the tooltip
go to the definition of waitAndRead
go to the definition of the return type (WorkResponse)

Before

The return value of waitAndRead is treated as Object
The definition of WorkResponse points to the .proto file
https://github.com/user-attachments/assets/386ddd4f-db38-40dd-8505-c3904d62612d

After

The return value of waitAndRead if a WorkResponse
The definition of WorkResponse points to both the .proto file and the generated Java file
https://github.com/user-attachments/assets/0853b964-c20b-4af9-a803-925dc6ff012f

coderabbitai · 2026-07-20T14:25:01Z

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tgodzik

Looks pretty great! An I can confirm it works. I have some overall suggestions, nothing blocking.

tgodzik · 2026-07-23T11:23:52Z

+   *   - `getFoo(+1).` -> `getFoo().`
+   *   - `setBar(+3).` -> `setBar().`
+   */
+  private def stripDisambiguators(symbol: String): String =


Do we need this? Shouldn't we find the correct definition anyway?

originally, stripDisambiguators was needed because there was no way to tell apart symbols related to overloaded methods (I think I've come across some case where a generated outline had two setters with the same names but different argument types)

I've added some logic to find the exact overload used by the caller based on the argument names and types, so we no longer need stripDisambiguators
f422d7a

I think the method order correspond to +1,+2 etc. We shouldn't need parameters:

Disambiguator is: Concatenation of a left parenthesis ((), a tag and a right parenthesis ()). If the definition is not overloaded, the tag is empty. Two definitions are overloaded if they have the same name and both require a disambiguator. If the definition is overloaded, the tag is computed from the order of appearance of overloads in the source code (see "Function declarations and definitions" below for an example): Empty string for the definition that appears first. +1 for the definition that appears second. +2 for the definition that appears third.

from https://scalameta.org/docs/semanticdb/specification#symbol-1

tgodzik · 2026-07-23T11:35:41Z

Also, looks like this fixes #8653 could you add a rename test as well?

Synthesize a Java outline from each .proto and materialize it as a read-only file under .metals/readonly, so go-to-definition on a proto-generated class (message, enum, gRPC stub) lands in the generated Java source alongside the .proto declaration. Route the materialized file to the proto's build target and feed the outlines through the turbine classpath so hover and completion resolve proto-generated types too. Works for every build tool with no build output and no configuration. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

The SemanticDB overload disambiguator carries no signature info and is computed independently at the call site (mtags-java) and when re-indexing the materialized outline (mtags), so it can disagree and the previous fix had to return every name-matching candidate instead of the one the user actually navigated to. Thread the call site's real resolved parameter names/types (MtagsIndexer.ParameterSignature) end-to-end through mtags-interfaces/mtags-shared/mtags-java into metals' DefinitionResult, and use them in DefinitionProviderProtobufSupport.findRange to narrow multiple name-matching candidates down to the one whose signature actually matches, comparing by dotted type-name suffix (the outline refers to sibling types by simple name, the call site always resolves fully qualified). Falls back to returning every name match, unchanged, whenever the new info is unavailable or ambiguous. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

The parser only recognized `syntax = "proto2"/"proto3";` at the top of a .proto file, so any file using Protobuf Editions (`edition = "2023";`) threw a ProtoError and failed to generate a Java outline entirely, breaking Java-file navigation for those files.

damiankus-vl · 2026-07-24T12:13:36Z

Also, looks like this fixes #8653 could you add a rename test as well?

addressed in a separate PR
#8730

damiankus-vl · 2026-07-24T13:08:43Z

-          syntax = Optional.of(parseSyntax());
+          syntax = Optional.of(parseSyntax("syntax"));
+          break;
+        case "edition":


in the Bazel project there's a proto file that uses the edition keyword
https://github.com/bazelbuild/bazel/blob/master/src/main/protobuf/execution_graph_writer.proto

It breaks Metals with the following error

2026-07-24 10:46:57.230 [info] 2026.07.24 10:46:57 WARN Failed to generate Java outline for proto /Users/dkus/Documents/Projects/bazel/src/main/protobuf/execution_graph_writer.proto scala.meta.internal.proto.diag.ProtoError: file:///Users/dkus/Documents/Projects/bazel/src/main/protobuf/execution_graph_writer.proto:15:1: Unexpected token: edition at scala.meta.internal.proto.parse.Parser.error(Parser.java:886) at scala.meta.internal.proto.parse.Parser.parseFile(Parser.java:92) at scala.meta.internal.proto.parse.Parser.parse(Parser.java:36)

Commit 2925ada should fix that

damiankus-vl force-pushed the improve-protobuf-support branch 2 times, most recently from b427446 to 6732291 Compare July 21, 2026 07:11

odisseus self-requested a review July 21, 2026 11:04

odisseus approved these changes Jul 22, 2026

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tgodzik requested changes Jul 23, 2026

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tgodzik mentioned this pull request Jul 23, 2026

Renaming Protobuf Type Leads to Exceptions #8653

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damiankus-vl force-pushed the improve-protobuf-support branch from 6732291 to c4562c0 Compare July 24, 2026 08:56

damiankus-vl and others added 2 commits July 24, 2026 13:50

damiankus-vl force-pushed the improve-protobuf-support branch from c4562c0 to 2925ada Compare July 24, 2026 11:51

damiankus-vl commented Jul 24, 2026

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feature: navigate to Java files materialized from .proto files#8699

feature: navigate to Java files materialized from .proto files#8699
damiankus-vl wants to merge 3 commits into
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damiankus-vl:improve-protobuf-support

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damiankus-vl commented Jul 20, 2026

DEMO

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