Add Context.Get generic functions

Author: aldas

context_generic.go

@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: MIT
+// SPDX-FileCopyrightText: © 2015 LabStack LLC and Echo contributors
+
+package echo
+
+import "errors"
+
+// ErrNonExistentKey is error that is returned when key does not exist
+var ErrNonExistentKey = errors.New("non existent key")
+
+// ErrInvalidKeyType is error that is returned when the value is not castable to expected type.
+var ErrInvalidKeyType = errors.New("invalid key type")
+
+// ContextGet retrieves a value from the context store or ErrNonExistentKey error the key is missing.
+// Returns ErrInvalidKeyType error if the value is not castable to type T.
+func ContextGet[T any](c Context, key string) (T, error) {
+	val := c.Get(key)
+	if val == any(nil) {
+		var zero T
+		return zero, ErrNonExistentKey
+	}
+
+	typed, ok := val.(T)
+	if !ok {
+		var zero T
+		return zero, ErrInvalidKeyType
+	}
+
+	return typed, nil
+}
+
+// ContextGetOr retrieves a value from the context store or returns a default value when the key
+// is missing. Returns ErrInvalidKeyType error if the value is not castable to type T.
+func ContextGetOr[T any](c Context, key string, defaultValue T) (T, error) {
+	typed, err := ContextGet[T](c, key)
+	if err == ErrNonExistentKey {
+		return defaultValue, nil
+	}
+	return typed, err
+}

context_generic_test.go

@@ -0,0 +1,73 @@
+package echo
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestContextGetOK(t *testing.T) {
+	e := New()
+	c := e.NewContext(nil, nil)
+
+	c.Set("key", int64(123))
+
+	v, err := ContextGet[int64](c, "key")
+	assert.NoError(t, err)
+	assert.Equal(t, int64(123), v)
+}
+
+func TestContextGetNonExistentKey(t *testing.T) {
+	e := New()
+	c := e.NewContext(nil, nil)
+
+	c.Set("key", int64(123))
+
+	v, err := ContextGet[int64](c, "nope")
+	assert.ErrorIs(t, err, ErrNonExistentKey)
+	assert.Equal(t, int64(0), v)
+}
+
+func TestContextGetInvalidCast(t *testing.T) {
+	e := New()
+	c := e.NewContext(nil, nil)
+
+	c.Set("key", int64(123))
+
+	v, err := ContextGet[bool](c, "key")
+	assert.ErrorIs(t, err, ErrInvalidKeyType)
+	assert.Equal(t, false, v)
+}
+
+func TestContextGetOrOK(t *testing.T) {
+	e := New()
+	c := e.NewContext(nil, nil)
+
+	c.Set("key", int64(123))
+
+	v, err := ContextGetOr[int64](c, "key", 999)
+	assert.NoError(t, err)
+	assert.Equal(t, int64(123), v)
+}
+
+func TestContextGetOrNonExistentKey(t *testing.T) {
+	e := New()
+	c := e.NewContext(nil, nil)
+
+	c.Set("key", int64(123))
+
+	v, err := ContextGetOr[int64](c, "nope", 999)
+	assert.NoError(t, err)
+	assert.Equal(t, int64(999), v)
+}
+
+func TestContextGetOrInvalidCast(t *testing.T) {
+	e := New()
+	c := e.NewContext(nil, nil)
+
+	c.Set("key", int64(123))
+
+	v, err := ContextGetOr[float32](c, "key", float32(999))
+	assert.ErrorIs(t, err, ErrInvalidKeyType)
+	assert.Equal(t, float32(0), v)
+}