Fix: Generate models for all JSON media types

As highlighted in #1168, we have some cases where JSON-compatible media
types aren't having their respective models generated, as we previously
only looked for `application/json`.

To resolve this, we can make sure that any media types that are
compatible with JSON (via our utility method) can have their types
generated.

This is a fix for #1168, which could also be deemed a feature. However,
as this has broken in the upgrade from v1.12.x to v1.13.x, this is being
treated as a feature.

Closes #1168.

internal/test/issues/issue-1168/doc.go

@@ -0,0 +1,3 @@
+package issue1168
+
+//go:generate go run github.com/deepmap/oapi-codegen/cmd/oapi-codegen --config=server.config.yaml spec.yaml

internal/test/issues/issue-1168/server.config.yaml

@@ -0,0 +1,5 @@
+package: issue1168
+output:
+  api.gen.go
+generate:
+  models: true

internal/test/issues/issue-1168/spec.yaml

@@ -0,0 +1,95 @@
+---
+# Copyright 2023 Coros, Corp. All Rights Reserved.
+#
+# Apache 2.0 Licensed; the portion included from
+# https://github.com/zalando/problem/ is MIT licensed
+#
+openapi: 3.0.3
+info:
+  version: 1.0.0
+  title: Test
+  description: Provides access to things
+  license:
+    name: Apache License 2.0
+    url: http://www.example.com/XXX
+
+servers:
+  - url: https://www.example.com/api
+    description: Production environment
+
+paths:
+  /v1/test:
+    get:
+      summary: Get it
+      responses:
+        '200':
+          description: Successful response
+          content:
+            text/plain:
+              type: string
+        '400':
+          $ref: '#/components/responses/Misc400Error'
+        '404':
+          $ref: '#/components/responses/Misc404Error'
+
+components:
+  responses:
+    Misc400Error:
+      description: Bad request
+      content:
+        application/problem+json:
+          schema:
+            $ref: '#/components/schemas/ProblemDetails'
+    Misc404Error:
+      description: Not found
+      content:
+        application/problem+json:
+          schema:
+            $ref: '#/components/schemas/ProblemDetails'
+
+  schemas:
+    # Fetched from https://opensource.zalando.com/problem/schema.yaml
+    # and slightly modified.
+    # Part of https://github.com/zalando/problem/; MIT License
+    ProblemDetails:
+      type: object
+      additionalProperties: true
+      properties:
+        type:
+          type: string
+          format: uri
+          description: >-
+            An absolute URI that identifies the problem type.  When dereferenced,
+            it SHOULD provide human-readable documentation for the problem type
+            (e.g., using HTML).
+          default: 'about:blank'
+          example: 'https://zalando.github.io/problem/constraint-violation'
+        title:
+          type: string
+          description: >-
+            A short, summary of the problem type. Written in english and readable
+            for engineers (usually not suited for non technical stakeholders and
+            not localized); example: Service Unavailable
+        status:
+          type: integer
+          format: int32
+          description: >-
+            The HTTP status code generated by the origin server for this occurrence
+            of the problem.
+          minimum: 100
+          maximum: 600
+          exclusiveMaximum: true
+          example: 503
+        detail:
+          type: string
+          description: >-
+            A human readable explanation specific to this occurrence of the
+            problem.
+          example: Connection to database timed out
+        instance:
+          type: string
+          format: uri
+          description: >-
+            An absolute URI that identifies the specific occurrence of the problem.
+            It may or may not yield further information if dereferenced.
+    # </MIT License>

pkg/codegen/codegen.go

@@ -28,6 +28,7 @@ import (
 	"strings"
 	"text/template"
 
+	"github.com/deepmap/oapi-codegen/pkg/util"
 	"github.com/getkin/kin-openapi/openapi3"
 	"golang.org/x/tools/imports"
 )
@@ -540,12 +541,15 @@ func GenerateTypesForResponses(t *template.Template, responses openapi3.Response
 		responseOrRef := responses[responseName]
 
 		// We have to generate the response object. We're only going to
-		// handle application/json media types here. Other responses should
+		// handle media types that conform to JSON. Other responses should
 		// simply be specified as strings or byte arrays.
 		response := responseOrRef.Value
-		jsonResponse, found := response.Content["application/json"]
-		if found {
-			goType, err := GenerateGoSchema(jsonResponse.Schema, []string{responseName})
+		for mediaType, response := range response.Content {
+			if !util.IsMediaTypeJson(mediaType) {
+				continue
+			}
+
+			goType, err := GenerateGoSchema(response.Schema, []string{responseName})
 			if err != nil {
 				return nil, fmt.Errorf("error generating Go type for schema in response %s: %w", responseName, err)
 			}
@@ -569,6 +573,7 @@ func GenerateTypesForResponses(t *template.Template, responses openapi3.Response
 				}
 				typeDef.TypeName = SchemaNameToTypeName(refType)
 			}
+
 			types = append(types, typeDef)
 		}
 	}
@@ -586,9 +591,12 @@ func GenerateTypesForRequestBodies(t *template.Template, bodies map[string]*open
 		// As for responses, we will only generate Go code for JSON bodies,
 		// the other body formats are up to the user.
 		response := requestBodyRef.Value
-		jsonBody, found := response.Content["application/json"]
-		if found {
-			goType, err := GenerateGoSchema(jsonBody.Schema, []string{requestBodyName})
+		for mediaType, body := range response.Content {
+			if !util.IsMediaTypeJson(mediaType) {
+				continue
+			}
+
+			goType, err := GenerateGoSchema(body.Schema, []string{requestBodyName})
 			if err != nil {
 				return nil, fmt.Errorf("error generating Go type for schema in body %s: %w", requestBodyName, err)
 			}
@@ -1048,9 +1056,12 @@ func GetRequestBodiesImports(bodies map[string]*openapi3.RequestBodyRef) (map[st
 	res := map[string]goImport{}
 	for _, r := range bodies {
 		response := r.Value
-		jsonBody, found := response.Content["application/json"]
-		if found {
-			imprts, err := GoSchemaImports(jsonBody.Schema)
+		for mediaType, body := range response.Content {
+			if !util.IsMediaTypeJson(mediaType) {
+				continue
+			}
+
+			imprts, err := GoSchemaImports(body.Schema)
 			if err != nil {
 				return nil, err
 			}
@@ -1064,9 +1075,12 @@ func GetResponsesImports(responses map[string]*openapi3.ResponseRef) (map[string
 	res := map[string]goImport{}
 	for _, r := range responses {
 		response := r.Value
-		jsonResponse, found := response.Content["application/json"]
-		if found {
-			imprts, err := GoSchemaImports(jsonResponse.Schema)
+		for mediaType, body := range response.Content {
+			if !util.IsMediaTypeJson(mediaType) {
+				continue
+			}
+
+			imprts, err := GoSchemaImports(body.Schema)
 			if err != nil {
 				return nil, err
 			}