Use early overrides to allow converting unsupported types.

example/override/.swaggo

@@ -0,0 +1,2 @@
+replace sql.NullString string
+replace sql.NullInt64 int64

example/override/docs/docs.go

@@ -0,0 +1,89 @@
+// Package docs GENERATED BY SWAG; DO NOT EDIT
+// This file was generated by swaggo/swag
+package docs
+
+import "github.com/swaggo/swag"
+
+const docTemplate = `{
+    "schemes": {{ marshal .Schemes }},
+    "swagger": "2.0",
+    "info": {
+        "description": "{{escape .Description}}",
+        "title": "{{.Title}}",
+        "termsOfService": "http://swagger.io/terms/",
+        "contact": {
+            "name": "API Support",
+            "url": "http://www.swagger.io/support",
+            "email": "support@swagger.io"
+        },
+        "license": {
+            "name": "Apache 2.0",
+            "url": "http://www.apache.org/licenses/LICENSE-2.0.html"
+        },
+        "version": "{{.Version}}"
+    },
+    "host": "{{.Host}}",
+    "basePath": "{{.BasePath}}",
+    "paths": {
+        "/testapi/update-product/{product_id}": {
+            "post": {
+                "consumes": [
+                    "application/json"
+                ],
+                "summary": "Update product attributes",
+                "operationId": "update-product",
+                "parameters": [
+                    {
+                        "type": "integer",
+                        "description": "Product ID",
+                        "name": "product_id",
+                        "in": "path",
+                        "required": true
+                    },
+                    {
+                        "description": " ",
+                        "name": "_",
+                        "in": "body",
+                        "required": true,
+                        "schema": {
+                            "$ref": "#/definitions/main.ProductUpdates"
+                        }
+                    }
+                ],
+                "responses": {}
+            }
+        }
+    },
+    "definitions": {
+        "main.ProductUpdates": {
+            "type": "object",
+            "properties": {
+                "description": {
+                    "type": "string"
+                },
+                "stock": {
+                    "type": "integer"
+                },
+                "type": {
+                    "type": "string"
+                }
+            }
+        }
+    }
+}`
+
+// SwaggerInfo holds exported Swagger Info so clients can modify it
+var SwaggerInfo = &swag.Spec{
+	Version:          "1.0",
+	Host:             "product_info.swagger.io",
+	BasePath:         "/v2",
+	Schemes:          []string{},
+	Title:            "Swagger Example API",
+	Description:      "This is a sample server for updating product information.",
+	InfoInstanceName: "swagger",
+	SwaggerTemplate:  docTemplate,
+}
+
+func init() {
+	swag.Register(SwaggerInfo.InstanceName(), SwaggerInfo)
+}

example/override/docs/swagger.json

@@ -0,0 +1,66 @@
+{
+    "swagger": "2.0",
+    "info": {
+        "description": "This is a sample server for updating product information.",
+        "title": "Swagger Example API",
+        "termsOfService": "http://swagger.io/terms/",
+        "contact": {
+            "name": "API Support",
+            "url": "http://www.swagger.io/support",
+            "email": "support@swagger.io"
+        },
+        "license": {
+            "name": "Apache 2.0",
+            "url": "http://www.apache.org/licenses/LICENSE-2.0.html"
+        },
+        "version": "1.0"
+    },
+    "host": "product_info.swagger.io",
+    "basePath": "/v2",
+    "paths": {
+        "/testapi/update-product/{product_id}": {
+            "post": {
+                "consumes": [
+                    "application/json"
+                ],
+                "summary": "Update product attributes",
+                "operationId": "update-product",
+                "parameters": [
+                    {
+                        "type": "integer",
+                        "description": "Product ID",
+                        "name": "product_id",
+                        "in": "path",
+                        "required": true
+                    },
+                    {
+                        "description": " ",
+                        "name": "_",
+                        "in": "body",
+                        "required": true,
+                        "schema": {
+                            "$ref": "#/definitions/main.ProductUpdates"
+                        }
+                    }
+                ],
+                "responses": {}
+            }
+        }
+    },
+    "definitions": {
+        "main.ProductUpdates": {
+            "type": "object",
+            "properties": {
+                "description": {
+                    "type": "string"
+                },
+                "stock": {
+                    "type": "integer"
+                },
+                "type": {
+                    "type": "string"
+                }
+            }
+        }
+    }
+}

example/override/docs/swagger.yaml

@@ -0,0 +1,45 @@
+basePath: /v2
+definitions:
+  main.ProductUpdates:
+    properties:
+      description:
+        type: string
+      stock:
+        type: integer
+      type:
+        type: string
+    type: object
+host: product_info.swagger.io
+info:
+  contact:
+    email: support@swagger.io
+    name: API Support
+    url: http://www.swagger.io/support
+  description: This is a sample server for updating product information.
+  license:
+    name: Apache 2.0
+    url: http://www.apache.org/licenses/LICENSE-2.0.html
+  termsOfService: http://swagger.io/terms/
+  title: Swagger Example API
+  version: "1.0"
+paths:
+  /testapi/update-product/{product_id}:
+    post:
+      consumes:
+      - application/json
+      operationId: update-product
+      parameters:
+      - description: Product ID
+        in: path
+        name: product_id
+        required: true
+        type: integer
+      - description: ' '
+        in: body
+        name: _
+        required: true
+        schema:
+          $ref: '#/definitions/main.ProductUpdates'
+      responses: {}
+      summary: Update product attributes
+swagger: "2.0"

example/override/handler.go

@@ -0,0 +1,30 @@
+package main
+
+import (
+	"database/sql"
+	"encoding/json"
+	"net/http"
+)
+
+type ProductUpdates struct {
+	Type        sql.NullString `json:"type"`
+	Description sql.NullString `json:"description"`
+	Stock       sql.NullInt64  `json:"stock"`
+}
+
+// UpdateProduct example
+// @Summary Update product attributes
+// @ID update-product
+// @Accept  json
+// @Param   product_id      path   int     true  "Product ID"
+// @Param   _      body ProductUpdates true  " "
+// @Router /testapi/update-product/{product_id} [post]
+func UpdateProduct(w http.ResponseWriter, r *http.Request) {
+	var pUpdates ProductUpdates
+	if err := json.NewDecoder(r.Body).Decode(&pUpdates); err != nil {
+		// write your code
+		return
+	}
+
+	// write your code
+}

example/override/main.go

@@ -0,0 +1,24 @@
+package main
+
+import (
+	"net/http"
+)
+
+// @title Swagger Example API
+// @version 1.0
+// @description This is a sample server with null types overridden with primitive types.
+// @termsOfService http://swagger.io/terms/
+
+// @contact.name API Support
+// @contact.url http://www.swagger.io/support
+// @contact.email support@swagger.io
+
+// @license.name Apache 2.0
+// @license.url http://www.apache.org/licenses/LICENSE-2.0.html
+
+// @host product_info.swagger.io
+// @BasePath /v2
+func main() {
+	http.HandleFunc("/testapi/update-product", UpdateProduct)
+	http.ListenAndServe(":8080", nil)
+}

parser.go

@@ -898,6 +898,11 @@ func convertFromSpecificToPrimitive(typeName string) (string, error) {
 }
 
 func (parser *Parser) getTypeSchema(typeName string, file *ast.File, ref bool) (*spec.Schema, error) {
+	if override, ok := parser.Overrides[typeName]; ok {
+		parser.debug.Printf("Override detected for %s: using %s instead", typeName, override)
+		typeName = override
+	}
+
 	if IsGolangPrimitiveType(typeName) {
 		return PrimitiveSchema(TransToValidSchemeType(typeName)), nil
 	}

parser_test.go

@@ -77,6 +77,34 @@ func TestSetOverrides(t *testing.T) {
 	assert.Equal(t, overrides, p.Overrides)
 }
 
+func TestOverrides_getTypeSchema(t *testing.T) {
+	t.Parallel()
+
+	overrides := map[string]string{
+		"sql.NullString": "string",
+	}
+
+	p := New(SetOverrides(overrides))
+
+	t.Run("Override sql.NullString by string", func(t *testing.T) {
+		t.Parallel()
+
+		s, err := p.getTypeSchema("sql.NullString", nil, false)
+		if assert.NoError(t, err) {
+			assert.Truef(t, s.Type.Contains("string"), "type sql.NullString should be overridden by string")
+		}
+	})
+
+	t.Run("Missing Override for sql.NullInt64", func(t *testing.T) {
+		t.Parallel()
+
+		_, err := p.getTypeSchema("sql.NullInt64", nil, false)
+		if assert.Error(t, err) {
+			assert.Equal(t, "cannot find type definition: sql.NullInt64", err.Error())
+		}
+	})
+}
+
 func TestParser_ParseDefinition(t *testing.T) {
 	p := New()
 
@@ -478,7 +506,7 @@ func TestParser_ParseProduceComment(t *testing.T) {
 	assert.Equal(t, parser.swagger.Produces, expected)
 }
 
-func TestParser_ParseGeneralAPIInfoCollectionFromat(t *testing.T) {
+func TestParser_ParseGeneralAPIInfoCollectionFormat(t *testing.T) {
 	t.Parallel()
 
 	parser := New()