Remove maxparam dependence from Context (#2611)

context.go

@@ -202,15 +202,29 @@ type Context interface {
 type context struct {
 	request  *http.Request
 	response *Response
-	path     string
-	pnames   []string
-	pvalues  []string
 	query    url.Values
-	handler  HandlerFunc
-	store    Map
 	echo     *Echo
 	logger   Logger
-	lock     sync.RWMutex
+
+	store Map
+	lock  sync.RWMutex
+
+	// following fields are set by Router
+
+	// path is route path that Router matched. It is empty string where there is no route match.
+	// Route registered with RouteNotFound is considered as a match and path therefore is not empty.
+	path string
+
+	// pnames length is tied to param count for the matched route
+	pnames []string
+
+	// Usually echo.Echo is sizing pvalues but there could be user created middlewares that decide to
+	// overwrite parameter by calling SetParamNames + SetParamValues.
+	// When echo.Echo allocated that slice it length/capacity is tied to echo.Echo.maxParam value.
+	//
+	// It is important that pvalues size is always equal or bigger to pnames length.
+	pvalues []string
+	handler HandlerFunc
 }
 
 const (
@@ -330,10 +344,6 @@ func (c *context) SetParamNames(names ...string) {
 	c.pnames = names
 
 	l := len(names)
-	if *c.echo.maxParam < l {
-		*c.echo.maxParam = l
-	}
-
 	if len(c.pvalues) < l {
 		// Keeping the old pvalues just for backward compatibility, but it sounds that doesn't make sense to keep them,
 		// probably those values will be overridden in a Context#SetParamValues
@@ -348,11 +358,11 @@ func (c *context) ParamValues() []string {
 }
 
 func (c *context) SetParamValues(values ...string) {
-	// NOTE: Don't just set c.pvalues = values, because it has to have length c.echo.maxParam at all times
+	// NOTE: Don't just set c.pvalues = values, because it has to have length c.echo.maxParam (or bigger) at all times
 	// It will brake the Router#Find code
 	limit := len(values)
-	if limit > *c.echo.maxParam {
-		limit = *c.echo.maxParam
+	if limit > len(c.pvalues) {
+		c.pvalues = make([]string, limit)
 	}
 	for i := 0; i < limit; i++ {
 		c.pvalues[i] = values[i]
@@ -643,8 +653,8 @@ func (c *context) Reset(r *http.Request, w http.ResponseWriter) {
 	c.path = ""
 	c.pnames = nil
 	c.logger = nil
-	// NOTE: Don't reset because it has to have length c.echo.maxParam at all times
-	for i := 0; i < *c.echo.maxParam; i++ {
+	// NOTE: Don't reset because it has to have length c.echo.maxParam (or bigger) at all times
+	for i := 0; i < len(c.pvalues); i++ {
 		c.pvalues[i] = ""
 	}
 }

context_test.go

@@ -653,36 +653,50 @@ func TestContextGetAndSetParam(t *testing.T) {
 	})
 }
 
-// Issue #1655
-func TestContextSetParamNamesShouldUpdateEchoMaxParam(t *testing.T) {
+func TestContextSetParamNamesEchoMaxParam(t *testing.T) {
 	e := New()
 	assert.Equal(t, 0, *e.maxParam)
 
 	expectedOneParam := []string{"one"}
 	expectedTwoParams := []string{"one", "two"}
 	expectedThreeParams := []string{"one", "two", ""}
-	expectedABCParams := []string{"A", "B", "C"}
 
-	c := e.NewContext(nil, nil)
-	c.SetParamNames("1", "2")
-	c.SetParamValues(expectedTwoParams...)
-	assert.Equal(t, 2, *e.maxParam)
-	assert.EqualValues(t, expectedTwoParams, c.ParamValues())
+	{
+		c := e.AcquireContext()
+		c.SetParamNames("1", "2")
+		c.SetParamValues(expectedTwoParams...)
+		assert.Equal(t, 0, *e.maxParam) // has not been changed
+		assert.EqualValues(t, expectedTwoParams, c.ParamValues())
+		e.ReleaseContext(c)
+	}
 
-	c.SetParamNames("1")
-	assert.Equal(t, 2, *e.maxParam)
-	// Here for backward compatibility the ParamValues remains as they are
-	assert.EqualValues(t, expectedOneParam, c.ParamValues())
+	{
+		c := e.AcquireContext()
+		c.SetParamNames("1", "2", "3")
+		c.SetParamValues(expectedThreeParams...)
+		assert.Equal(t, 0, *e.maxParam) // has not been changed
+		assert.EqualValues(t, expectedThreeParams, c.ParamValues())
+		e.ReleaseContext(c)
+	}
 
-	c.SetParamNames("1", "2", "3")
-	assert.Equal(t, 3, *e.maxParam)
-	// Here for backward compatibility the ParamValues remains as they are, but the len is extended to e.maxParam
-	assert.EqualValues(t, expectedThreeParams, c.ParamValues())
+	{ // values is always same size as names length
+		c := e.NewContext(nil, nil)
+		c.SetParamValues([]string{"one", "two"}...) // more values than names should be ok
+		c.SetParamNames("1")
+		assert.Equal(t, 0, *e.maxParam) // has not been changed
+		assert.EqualValues(t, expectedOneParam, c.ParamValues())
+	}
 
-	c.SetParamValues("A", "B", "C", "D")
-	assert.Equal(t, 3, *e.maxParam)
-	// Here D shouldn't be returned
-	assert.EqualValues(t, expectedABCParams, c.ParamValues())
+	e.GET("/:id", handlerFunc)
+	assert.Equal(t, 1, *e.maxParam) // has not been changed
+
+	{
+		c := e.NewContext(nil, nil)
+		c.SetParamValues([]string{"one", "two"}...)
+		c.SetParamNames("1")
+		assert.Equal(t, 1, *e.maxParam) // has not been changed
+		assert.EqualValues(t, expectedOneParam, c.ParamValues())
+	}
 }
 
 func TestContextFormValue(t *testing.T) {