grpc-ecosystem/grpc-gateway · error

at least one input is required

Error message

at least one input is required

What it means

Argument-validation error at the top of Merge: the inputs slice is empty. Merge needs at least one OpenAPI 3.1 document to seed the merged output (first input's info/servers/externalDocs are kept); with zero inputs there is nothing to produce, so it refuses instead of emitting an empty document.

Source

Thrown at openapiv3-merge/internal/merge/merge.go:55

)

// Input is a single OpenAPI 3.1 JSON document to merge.
type Input struct {
	// Name identifies the document in error messages, typically the path
	// the document was loaded from.
	Name string
	// Data is the raw JSON content of the document.
	Data []byte
}

// Merge combines inputs into a single OpenAPI 3.1 JSON document and returns
// its pretty-printed bytes (two-space indent, matching protoc-gen-openapiv3).
//
// At least one input is required. The first input's `info`, `servers`, and
// `externalDocs` are kept in the merged document.
func Merge(inputs []Input) ([]byte, error) {
	if len(inputs) == 0 {
		return nil, errors.New("at least one input is required")
	}
	docs := make([]*document, len(inputs))
	for i, in := range inputs {
		d, err := parse(in)
		if err != nil {
			return nil, err
		}
		docs[i] = d
	}
	merged, err := mergeAll(docs)
	if err != nil {
		return nil, err
	}
	// Drop empty container fields so encoding/json's omitempty omits them.
	if merged.Paths.len() == 0 {
		merged.Paths = nil
	}
	if merged.Webhooks.len() == 0 {

View on GitHub (pinned to a58a4436a3)

Solutions

1. Pass at least one Input to Merge.
2. In the CLI, provide at least one FILE argument so run() builds a non-empty inputs slice.

When it happens

Trigger: Thrown at openapiv3-merge/internal/merge/merge.go:55 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of grpc-ecosystem/grpc-gateway@a58a4436a3 (2026-09-02). Data as JSON: /api/errors/604bde7972dc130e. Report an issue: GitHub.