BindStyledParameterWithOptions double-decodes path parameters

[reinkrul]

When a path parameter contains percent-encoded characters (in the original value), BindStyledParameterWithOptions causes the original percent characters to be decoded as if they were URL path encoded. This either causes the original value to be lost or a HTTP error 400 in case the characer can't be decoded. E.g., if a path parameter were a (fictional) discount ("/checkout/" + url.PathEscape("15%off")), a HTTP error 400 occurs. Or url.PathEscape("discount%20") would be received in the server interface as "discount " (decoded to a space).

This is caused by BindStyledParameterWithOptions which uses the path parameters from Echo (didn't test other HTTP servers) to unescape the parameters, which Echo already did. It does not occur with query parameters.

Example

OpenAPI spec:

openapi: "3.0.1"
paths:
  /test/{param1}:
    parameters:
      - name: param1
        in: path
        required: true
        schema:
          type: string
    get:
      operationId: test
      responses:
        204:
          description: good

Unit test:

package issueXX_test

import (
	"context"
	issueXX "github.com/deepmap/oapi-codegen/v2/internal/test/issues/issue-XX"
	"github.com/labstack/echo/v4"
	"github.com/stretchr/testify/require"
	"net/http"
	"net/http/httptest"
	"net/url"
	"sync/atomic"
	"testing"

	"github.com/stretchr/testify/assert"
)

type serverImplementation struct {
	param1 atomic.Value
}

var _ issueXX.StrictServerInterface = &serverImplementation{}

func (s *serverImplementation) Test(_ context.Context, request issueXX.TestRequestObject) (issueXX.TestResponseObject, error) {
	s.param1.Store(request.Param1)
	return issueXX.Test204Response{}, nil
}

func TestIssueXX(t *testing.T) {
	impl := &serverImplementation{}
	e := echo.New()
	issueXX.RegisterHandlers(e, issueXX.NewStrictHandler(impl, nil))
	svr := httptest.NewServer(e)
	defer svr.Close()

	const expected = "discount%20"
	httpResponse, err := http.Get(svr.URL + "/test/" + url.PathEscape(expected))
	require.NoError(t, err)
	require.Equal(t, http.StatusNoContent, httpResponse.StatusCode)
	assert.Equal(t, expected, impl.param1.Load(), "path unescape incorrect")
}

Test output:

        	Error:      	Not equal: 
        	            	expected: "discount%20"
        	            	actual  : "discount "

Solution

BindStyledParameterWithOptions should not unescape the value (at least for Echo).