openapi3filter: support primitive parsing for individual text like parts in multipart/form-data (#1090)

* Add primitive parsing

* fix check

---------

Co-authored-by: Nathan Meheus <[email protected]>

Author: nmeheus

openapi3filter/issue949_test.go

@@ -0,0 +1,116 @@
+package openapi3filter_test
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"mime/multipart"
+	"net/http"
+	"net/textproto"
+	"strings"
+	"testing"
+
+	"github.com/getkin/kin-openapi/openapi3"
+	"github.com/getkin/kin-openapi/openapi3filter"
+	"github.com/getkin/kin-openapi/routers/gorillamux"
+	"github.com/stretchr/testify/require"
+)
+
+const testSchema = `
+openapi: 3.0.0
+info:
+  title: 'Validator'
+  version: 0.0.1
+paths:
+  /test:
+    post:
+      requestBody:
+        required: true
+        content:
+          multipart/form-data:
+            schema:
+              type: object
+              properties:
+                file:
+                  type: string
+                  format: binary
+                counts:
+                  type: object
+                  properties:
+                    name:
+                      type: string
+                    count:
+                      type: integer
+                primitive:
+                  type: integer
+      responses:
+        '200':
+          description: OK
+`
+
+type count struct {
+	Name  string `json:"name"`
+	Count int    `json:"count"`
+}
+
+func TestIssue949(t *testing.T) {
+	loader := openapi3.NewLoader()
+	doc, err := loader.LoadFromData([]byte(testSchema))
+	require.NoError(t, err)
+
+	err = doc.Validate(context.Background())
+	require.NoError(t, err)
+
+	router, err := gorillamux.NewRouter(doc)
+	require.NoError(t, err)
+
+	body := &bytes.Buffer{}
+	writer := multipart.NewWriter(body)
+
+	// Add the counts object to the request body
+	h := make(textproto.MIMEHeader)
+	h.Set("Content-Disposition", fmt.Sprintf(`form-data; name="%s"`, "counts"))
+	h.Set("Content-Type", "application/json")
+	fw, err := writer.CreatePart(h)
+	require.NoError(t, err)
+
+	countStruct := count{Name: "foo", Count: 7}
+	countBody, err := json.Marshal(countStruct)
+	require.NoError(t, err)
+	_, err = fw.Write(countBody)
+	require.NoError(t, err)
+
+	// Add the file to the request body
+	fw, err = writer.CreateFormFile("file", "hello.txt")
+	require.NoError(t, err)
+
+	_, err = io.Copy(fw, strings.NewReader("hello"))
+	require.NoError(t, err)
+
+	// Add the primitive integer to the request body
+	fw, err = writer.CreateFormField("primitive")
+	require.NoError(t, err)
+	_, err = fw.Write([]byte("1"))
+	require.NoError(t, err)
+
+	writer.Close()
+
+	req, _ := http.NewRequest(http.MethodPost, "/test", bytes.NewReader(body.Bytes()))
+	req.Header.Set("Content-Type", writer.FormDataContentType())
+
+	route, pathParams, err := router.FindRoute(req)
+	require.NoError(t, err)
+
+	reqBody := route.Operation.RequestBody.Value
+
+	requestValidationInput := &openapi3filter.RequestValidationInput{
+		Request:    req,
+		PathParams: pathParams,
+		Route:      route,
+	}
+
+	err = openapi3filter.ValidateRequestBody(context.TODO(), requestValidationInput, reqBody)
+	require.NoError(t, err)
+}

openapi3filter/req_resp_decoder.go

@@ -17,7 +17,7 @@ import (
 	"strconv"
 	"strings"
 
-	"github.com/oasdiff/yaml3"
+	yaml "github.com/oasdiff/yaml3"
 
 	"github.com/getkin/kin-openapi/openapi3"
 )
@@ -1472,13 +1472,26 @@ func MultipartBodyDecoder(body io.Reader, header http.Header, schema *openapi3.S
 			}
 		}
 
+		partHeader := http.Header(part.Header)
 		var value any
-		if _, value, err = decodeBody(part, http.Header(part.Header), valueSchema, subEncFn); err != nil {
+		if _, value, err = decodeBody(part, partHeader, valueSchema, subEncFn); err != nil {
 			if v, ok := err.(*ParseError); ok {
 				return nil, &ParseError{path: []any{name}, Cause: v}
 			}
 			return nil, fmt.Errorf("part %s: %w", name, err)
 		}
+
+		// Parse primitive types when no content type is explicitely provided, or the content type is set to text/plain
+		contentType := partHeader.Get(headerCT)
+		if contentType == "" || contentType == "text/plain" {
+			if value, err = parsePrimitive(value.(string), valueSchema); err != nil {
+				if v, ok := err.(*ParseError); ok {
+					return nil, &ParseError{path: []any{name}, Cause: v}
+				}
+				return nil, fmt.Errorf("part %s: %w", name, err)
+			}
+		}
+
 		values[name] = append(values[name], value)
 	}