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pkg/gateway/problem/problem.go

Source​

Overview​

What: Helpers for emitting RFC 7807 Problem+JSON responses with gateway-specific fields (notably traceId).

Why: Standardizes error responses across handlers and middleware so clients see consistent shape and tracing metadata.

How: Defines a Response struct and a Write helper that encodes it as application/problem+json.

Contents​

Imports​

import block 1​

pkg/gateway/problem/problem.go#L6
import (
	"encoding/json"
	"net/http"
)

Types​

type block 1​

pkg/gateway/problem/problem.go#L12
type Response struct {
	Type     string `json:"type"`
	Title    string `json:"title"`
	Status   int    `json:"status"`
	Detail   string `json:"detail,omitempty"`
	Instance string `json:"instance,omitempty"`
	TraceID  string `json:"traceId,omitempty"`
}

Response​

What: JSON shape for the gateway's Problem+JSON responses.

Why: Provides a typed, consistent error payload including trace correlation (traceId) and instance path (instance).

How: Used by Write and referenced by code that wants to emit RFC 7807 style responses.

Functions and Methods​

Write​

What: Writes an RFC 7807 Problem+JSON response to an http.ResponseWriter.

Why: Centralizes content-type, status, and JSON structure so call sites stay small and consistent.

How: Builds a Response with type set to about:blank, sets headers, writes status code, and JSON-encodes the body.

pkg/gateway/problem/problem.go#L22
func Write(w http.ResponseWriter, status int, title, detail, traceID, instance string) {
	resp := Response{
		Type:     "about:blank",
		Title:    title,
		Status:   status,
		Detail:   detail,
		Instance: instance,
		TraceID:  traceID,
	}

	w.Header().Set("Content-Type", "application/problem+json")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(resp)
}

Walkthrough​

The list below documents the statements inside the function body, including nested blocks and inline closures.

  • L23: resp := Response{ Type: "about:blank", Title: title, Status: status, Detail: detail, Instance: instance, TraceID: traceID, }
    • What: Defines resp.
    • Why: Keeps intermediate state available for later steps in the function.
    • How: Evaluates the right-hand side expressions and stores results in the left-hand variables.
  • L32: w.Header().Set("Content-Type", "application/problem+json")
    • What: Calls w.Header().Set.
    • Why: Performs side effects or delegates work to a helper.
    • How: Executes the expression statement.
  • L33: w.WriteHeader(status)
    • What: Calls w.WriteHeader.
    • Why: Performs side effects or delegates work to a helper.
    • How: Executes the expression statement.
  • L34: _ = json.NewEncoder(w).Encode(resp)
    • What: Assigns _.
    • Why: Keeps intermediate state available for later steps in the function.
    • How: Evaluates the right-hand side expressions and stores results in the left-hand variables.

Reference​

Neighboring source​