tpl: Add reflect namespace

Add a reflect namespace that offers a two boolean functions for
testing if a value is a map or slice.

Fixes #4081

6 files changed, 230 insertions, 0 deletions

diff --git a/docs/content/en/functions/reflect.IsMap.md b/docs/content/en/functions/reflect.IsMap.md
new file mode 100644
index 000000000..d75b842b4
--- /dev/null
+++ b/docs/content/en/functions/reflect.IsMap.md
@@ -0,0 +1,25 @@
+---
+title: reflect.IsMap
+description: Reports if a value is a map.
+godocref:
+date: 2018-11-28
+publishdate: 2018-11-28
+lastmod: 2018-11-28
+categories: [functions]
+menu:
+  docs:
+    parent: "functions"
+keywords: [reflect, reflection, kind]
+signature: ["reflect.IsMap INPUT"]
+workson: []
+hugoversion: "v0.53"
+relatedfuncs: [reflect.IsSlice]
+deprecated: false
+---
+
+`reflect.IsMap` reports if `VALUE` is a map.  Returns a boolean.
+
+```
+{{ reflect.IsMap (dict "key" "value") }} → true
+{{ reflect.IsMap "yo" }} → false
+```
diff --git a/docs/content/en/functions/reflect.IsSlice.md b/docs/content/en/functions/reflect.IsSlice.md
new file mode 100644
index 000000000..27d6aea21
--- /dev/null
+++ b/docs/content/en/functions/reflect.IsSlice.md
@@ -0,0 +1,25 @@
+---
+title: reflect.IsSlice
+description: Reports if a value is a slice.
+godocref:
+date: 2018-11-28
+publishdate: 2018-11-28
+lastmod: 2018-11-28
+categories: [functions]
+menu:
+  docs:
+    parent: "functions"
+keywords: [reflect, reflection, kind]
+signature: ["reflect.IsSlice INPUT"]
+workson: []
+hugoversion: "0.53"
+relatedfuncs: [reflect.IsMap]
+deprecated: false
+---
+
+`reflect.IsSlice` reports if `VALUE` is a slice.  Returns a boolean.
+
+```
+{{ reflect.IsSlice (slice 1 2 3) }} → true
+{{ reflect.IsSlice "yo" }} → false
+```
diff --git a/tpl/reflect/init.go b/tpl/reflect/init.go
new file mode 100644
index 000000000..4c639577b
--- /dev/null
+++ b/tpl/reflect/init.go
@@ -0,0 +1,50 @@
+// Copyright 2018 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package reflect
+
+import (
+	"github.com/gohugoio/hugo/deps"
+	"github.com/gohugoio/hugo/tpl/internal"
+)
+
+const name = "reflect"
+
+func init() {
+	f := func(d *deps.Deps) *internal.TemplateFuncsNamespace {
+		ctx := New()
+
+		ns := &internal.TemplateFuncsNamespace{
+			Name:    name,
+			Context: func(args ...interface{}) interface{} { return ctx },
+		}
+
+		ns.AddMethodMapping(ctx.IsMap,
+			nil,
+			[][2]string{
+				{`{{ if reflect.IsMap (dict "a" 1) }}Map{{ end }}`, `Map`},
+			},
+		)
+
+		ns.AddMethodMapping(ctx.IsSlice,
+			nil,
+			[][2]string{
+				{`{{ if reflect.IsSlice (slice 1 2 3) }}Slice{{ end }}`, `Slice`},
+			},
+		)
+
+		return ns
+	}
+
+	internal.AddTemplateFuncsNamespace(f)
+}
diff --git a/tpl/reflect/init_test.go b/tpl/reflect/init_test.go
new file mode 100644
index 000000000..4357200ab
--- /dev/null
+++ b/tpl/reflect/init_test.go
@@ -0,0 +1,39 @@
+// Copyright 2017 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package reflect
+
+import (
+	"testing"
+
+	"github.com/gohugoio/hugo/common/loggers"
+	"github.com/gohugoio/hugo/deps"
+	"github.com/gohugoio/hugo/tpl/internal"
+	"github.com/stretchr/testify/require"
+)
+
+func TestInit(t *testing.T) {
+	var found bool
+	var ns *internal.TemplateFuncsNamespace
+
+	for _, nsf := range internal.TemplateFuncsNamespaceRegistry {
+		ns = nsf(&deps.Deps{Log: loggers.NewErrorLogger()})
+		if ns.Name == name {
+			found = true
+			break
+		}
+	}
+
+	require.True(t, found)
+	require.IsType(t, &Namespace{}, ns.Context())
+}
diff --git a/tpl/reflect/reflect.go b/tpl/reflect/reflect.go
new file mode 100644
index 000000000..17646e9a0
--- /dev/null
+++ b/tpl/reflect/reflect.go
@@ -0,0 +1,36 @@
+// Copyright 2018 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package reflect
+
+import (
+	"reflect"
+)
+
+// New returns a new instance of the reflect-namespaced template functions.
+func New() *Namespace {
+	return &Namespace{}
+}
+
+// Namespace provides template functions for the "reflect" namespace.
+type Namespace struct{}
+
+// IsMap reports whether v is a map.
+func (ns *Namespace) IsMap(v interface{}) bool {
+	return reflect.ValueOf(v).Kind() == reflect.Map
+}
+
+// IsSlice reports whether v is a slice.
+func (ns *Namespace) IsSlice(v interface{}) bool {
+	return reflect.ValueOf(v).Kind() == reflect.Slice
+}
diff --git a/tpl/reflect/reflect_test.go b/tpl/reflect/reflect_test.go
new file mode 100644
index 000000000..9b2ad97a6
--- /dev/null
+++ b/tpl/reflect/reflect_test.go
@@ -0,0 +1,55 @@
+// Copyright 2018 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package reflect
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+var ns = New()
+
+type tstNoStringer struct{}
+
+func TestIsMap(t *testing.T) {
+	for i, test := range []struct {
+		v      interface{}
+		expect interface{}
+	}{
+		{map[int]int{1: 1}, true},
+		{"foo", false},
+		{nil, false},
+	} {
+		errMsg := fmt.Sprintf("[%d] %v", i, test)
+		result := ns.IsMap(test.v)
+		assert.Equal(t, test.expect, result, errMsg)
+	}
+}
+
+func TestIsSlice(t *testing.T) {
+	for i, test := range []struct {
+		v      interface{}
+		expect interface{}
+	}{
+		{[]int{1, 2}, true},
+		{"foo", false},
+		{nil, false},
+	} {
+		errMsg := fmt.Sprintf("[%d] %v", i, test)
+		result := ns.IsSlice(test.v)
+		assert.Equal(t, test.expect, result, errMsg)
+	}
+}