grpc-ecosystem/grpc-gateway

Support mapping request body to map type

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#765 opened on Oct 2, 2018

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Description

Is there a way tomap the message body to a keyed map? I.e. with a proto definition containing:

    rpc UpdateConfig (ServiceConfig) returns (OpResult) {
        option (google.api.http) = {
			post: "/v1/robotctl/services/configure"
			body: "config"
		};
    }

message ServiceConfig {
    ServicesReq services            = 1;
    map<string, string> config                   = 2;
}

The idea being that the body of the received message would map to a key in the, eg map<config, body_of_message>

Currently on compiling for grpc-gateway, the following error is thrown - which is odd given that there is no repeated element:

--grpc-gateway_out: repeated field not allowed in field path: config in config

Contributor guide

Tech stack
gogrpcrest api
Domain
backendapitooling
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
basic Goprotobuf familiaritygRPC concepts
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
The issue is about a protobuf map field in a gRPC HTTP annotation causing a compilation error 'repeated field not allowed in field path'. The error is likely from the code that validates field paths in the grpc gateway generator. Look for where this error message is defined (e.g., in protoc gen grpc gateway/internal/gengateway/template.go or similar). Understand how the generator processes field paths and why map fields are incorrectly treated as repeated. Check if there are any existing PRs or comments that discuss this. The fix would involve allowing map fields in body paths or properly distinguishing them from repeated fields.