echo: SetParamValues function throwing index out of range [0] with length 0 error

Issue Description

Hi,

I’ currently encountering an issue when setting parameter values via SetParamValues function. This is frequently used by my test cases, hence, tests are all failing.

Checklist

• Dependencies installed
• No typos
• Searched existing issues and docs

Expected behaviour

Should be able to set parameter values via SetParamValues function

Actual behaviour

SetParamValues function throws runtime error: index out of range [0] with length 0

Steps to reproduce

1. Create a folder inside your go source path.
2. Copy the codes below into files handler.go and handler_test.go and store them inside that folder.
3. cd yourfolder
4. go test -run ^(TestGetUser)$ -v

It will show this test logs afterwards:

=== RUN TestGetUser — FAIL: TestGetUser (0.00s) panic: runtime error: index out of range [0] with length 0 [recovered] panic: runtime error: index out of range [0] with length 0

goroutine 20 [running]: testing.tRunner.func1(0xc00010e100) /usr/local/Cellar/go/1.13.3/libexec/src/testing/testing.go:874 +0x3a3 panic(0x1387d40, 0xc0000c4380) /usr/local/Cellar/go/1.13.3/libexec/src/runtime/panic.go:679 +0x1b2 github.com/labstack/echo.(*context).SetParamValues(0xc0000bd180, 0xc00008d2b0, 0x1, 0x1) /Users/sonnysidramos/go/src/github.com/labstack/echo/context.go:317 +0x93 bitbucket.org/pulseid/echotest.TestGetUser(0xc00010e100) /Users/sonnysidramos/go/src/bitbucket.org/pulseid/echotest/handler_test.go:27 +0x307 testing.tRunner(0xc00010e100, 0x13ce2a0) /usr/local/Cellar/go/1.13.3/libexec/src/testing/testing.go:909 +0xc9 created by testing.(*T).Run /usr/local/Cellar/go/1.13.3/libexec/src/testing/testing.go:960 +0x350 exit status 2

Working code to debug

handler.go

package handler

import (
	"net/http"

	"github.com/labstack/echo"
)

type (
	User struct {
		Name  string `json:"name" form:"name"`
		Email string `json:"email" form:"email"`
	}
	handler struct {
		db map[string]*User
	}
)

func (h *handler) getUser(c echo.Context) error {
	email := c.Param("email")
	user := h.db[email]
	if user == nil {
		return echo.NewHTTPError(http.StatusNotFound, "user not found")
	}
	return c.JSON(http.StatusOK, user)
}

handler_test.go:

package handler

import (
	"net/http"
	"net/http/httptest"
	"testing"

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

var (
	mockDB = map[string]*User{
		"jon@labstack.com": &User{"Jon Snow", "jon@labstack.com"},
	}
	userJSON = `{"name":"Jon Snow","email":"jon@labstack.com"}`
)

func TestGetUser(t *testing.T) {
	// Setup
	e := echo.New()
	req := httptest.NewRequest(http.MethodGet, "/", nil)
	rec := httptest.NewRecorder()
	c := e.NewContext(req, rec)
	c.SetPath("/users/:email")
	c.SetParamNames("email")
	c.SetParamValues("jon@labstack.com")
	h := &handler{mockDB}

	// Assertions
	if assert.NoError(t, h.getUser(c)) {
		assert.Equal(t, http.StatusOK, rec.Code)
		assert.Equal(t, userJSON, rec.Body.String())
	}
}

Version/commit

https://github.com/labstack/echo/commit/8d7f05e5336fa9a05c6ca5a610a0c5140c01bfc3