npm NuGet v1.0.0 MIT

@metaengine/protobuf-fetch

Protobuf 3 → framework-agnostic TypeScript services and message types over the gRPC/Connect protocol on native Fetch. Zero dependencies, tree-shakeable, runs on Node, browsers, Vite, SvelteKit, and Next.js.

Protobuf 3.xMetaEngine IRTypeScript · Fetch
Install

Pick your registry

The same generator, published to every ecosystem we support. Install however your project expects.

npmPrimary@metaengine/protobuf-fetch
$npm install @metaengine/protobuf-fetch
v1.0.0
NuGetMetaEngine.TypeScript.Protobuf.Fetch
$dotnet add package MetaEngine.TypeScript.Protobuf.Fetch
v1.0.0
Usage

Drive it from the CLI or programmatically

npm ships a zero-config CLI. NuGet ships the same generator as a C# fluent API — same options, same output.

npm · npx · CI-friendly

After install, point the CLI at your OpenAPI spec. It writes the generated tree to your chosen output directory.

Basic syntax
terminal
npx @metaengine/protobuf-fetch <input> <output> [options]

Generates framework-agnostic TypeScript services and message types from Protobuf 3 .proto files, using gRPC/Connect over native Fetch.

Quick examples
Generate from a .proto file
npx @metaengine/protobuf-fetch service.proto ./src/api
With Vite, result pattern and middleware
npx @metaengine/protobuf-fetch service.proto ./src/api \
  --import-meta-env \
  --base-url-env VITE_API_URL \
  --result-pattern \
  --middleware \
  --documentation
Production setup with auth, timeout and headers
npx @metaengine/protobuf-fetch service.proto ./src/api \
  --bearer-auth API_TOKEN \
  --custom-header X-Tenant-ID=TENANT_ID \
  --timeout 30 \
  --error-handling
CLI options
Option
Description
--base-url-env <name>
Environment variable name for base URL [default: API_BASE_URL]
--service-suffix <suffix>
Service naming suffix [default: Service]
--options-threshold <n>
Parameter count to use options object [default: 4]
--documentation
Generate JSDoc comments
--import-meta-env
Use import.meta.env for env access (Vite, SvelteKit, Next.js 15+)
--result-pattern
Return ApiResult<T> instead of T for structured error handling
--middleware
Emit onRequest / onResponse / onError hooks in the generated client
--error-handling
Enable gRPC-native error handling keyed on gRPC status codes
--bearer-auth <env-var-name>
Bearer token from env var (adds Authorization header to all requests)
--basic-auth <userEnv:passEnv>
Basic auth from env vars. Format: <username-env>:<password-env> (e.g. API_USER:API_PASS)
--timeout <seconds>
Request timeout in seconds for all operations
--custom-header <header=envVarName>
Static header from env var. Repeatable (e.g. X-Tenant-ID=TENANT_ID)
--date-transformation
Convert google.protobuf.Timestamp fields in responses to JavaScript Date objects
--types-barrel
Emit an index.ts barrel per folder plus a root index.ts re-exporting everything
--type-mapping <mapping>
Override TS type for a protobuf type. Repeatable. Targets: string · number · Date · bigint · boolean (e.g. google.protobuf.Timestamp=string)
--clean
Clean output directory (remove files not in generation)
--verbose
Enable verbose logging
--help, -h
Show help message
Options reference

Every knob, documented

Every option is available on the C# fluent API as a method, and most are also exposed as CLI flags. Cross-cutting auth, headers, retries and timeouts apply across frameworks.

Fetch Options

5
  • WithBaseUrlEnvVar(string)Environment variable name for base URL (default: "API_BASE_URL"). Enables getDefaultClient() lazy singleton.
  • WithImportMetaEnv()Use import.meta.env instead of process.env (Vite, SvelteKit, Next.js 15+)
  • WithResultPattern()Return ApiResult<T> for structured error handling without exceptions
  • WithMiddleware()Emit onRequest / onResponse / onError hooks in the generated client
  • WithResponseDateTransformation()Convert google.protobuf.Timestamp fields in responses to Date objects

Auth · Headers · Resilience

9
  • WithErrorHandling()Enable gRPC-native error handling keyed on gRPC status codes (NOT_FOUND / PERMISSION_DENIED → null · INVALID_ARGUMENT / FAILED_PRECONDITION → error body · UNAUTHENTICATED / INTERNAL / UNAVAILABLE → throw)
  • WithErrorHandling(grpc => grpc...)Tune the gRPC taxonomy: ReturnNullForCodes(...) · ReturnErrorForCodes(...) · ThrowForCodes(...) · MapGrpcCode(code, behavior). Overrides merge on top of the defaults
  • WithBearerAuth()Bearer token from env var (default API_TOKEN) — adds Authorization header
  • WithBearerAuth(string)Bearer token from a specific env var name
  • WithBearerAuth(string, string)Bearer token with custom header name
  • WithBasicAuth(string, string)HTTP Basic auth from username + password env vars
  • WithCustomHeader(string, string)Static header from env var. Repeatable (e.g. X-Tenant-ID ← TENANT_ID)
  • WithTimeout(double)Request timeout in seconds, emitted as a grpc-timeout header on every call
  • WithTimeout(double?, double?, double?, double?)Granular timeout: connect · read · write · pool

Protobuf Options

5
  • WithDocumentation()Generate JSDoc comments from .proto field and service descriptions
  • WithTypeFilter(Func)Filter extracted proto types before registration — only types returning true are generated
  • WithTypeMapping(string, Type)Override the TS mapping for a protobuf well-known type by fully-qualified name (e.g. google.protobuf.Timestamp → string)
  • WithMethodNames(Func)Custom method naming rule
  • WithOptionsObjectThreshold(int)Parameter count for options object (default: 4)

TypeScript Output

1
  • WithTypesBarrel()Emit an index.ts barrel per folder plus a root index.ts re-exporting everything

Naming Transformations

3
  • Types(Func)Transform type names
  • Paths(Func)Transform output paths
  • FileNames(Func)Transform file names

File Management

5
  • CleanDestination()Clean output directory before generation
  • AlwaysOverwrite()Always overwrite existing files
  • OnlyWhenModelChanged()Update only when model changes
  • OnlyWhenNew()Write only new files, preserve existing
  • CleanDirectories(...)Clean specific subdirectories

Diagnostics

1
  • EnableVerboseLogging()Enable detailed logging
Features

Why this package is different

Deterministic output
Same spec + same options produce byte-identical files. Safe to commit, safe to diff in review, safe to cache in CI.
Tree-shakeable
One file per tag (or per operation) means bundlers drop unused code at build time. No runtime dispatch table.
Zero runtime
Validation and clients opt in. The default emit is pure types with no dependency surface beyond your HTTP lib.
Flexible naming
Case conventions configurable per role — types, properties, operations, enums. Idiomatic in the target by default.
Type resolution
Discriminated unions for oneOf, proper nullability, bigint when the spec mandates it, refs flattened only when safe.
Semver-honest
Spec diff drives the version bump. Additive changes = minor, removed ops = major. Never a surprise in your lockfile.