Merge pull request #492 from hairyhenderson/tmpl-exec-func-444-485

New tmpl.Exec function

5 files changed, 183 insertions, 2 deletions

diff --git a/docs-src/content/functions/tmpl.yml b/docs-src/content/functions/tmpl.yml
index 962fefaf..3bf2f9fa 100644
--- a/docs-src/content/functions/tmpl.yml
+++ b/docs-src/content/functions/tmpl.yml
@@ -3,6 +3,26 @@ title: template functions
 preamble: |
   Functions for defining or executing templates.
 funcs:
+  - name: tmpl.Exec
+    description: |
+      Execute (render) the named template. This is equivalent to using the [`template`](https://golang.org/pkg/text/template/#hdr-Actions) action, except the result is returned as a string.
+
+      This allows for post-processing of templates.
+    pipeline: true
+    arguments:
+      - name: name
+        required: true
+        description: The template's name.
+      - name: context
+        required: false
+        description: The context to use.
+    examples:
+      - |
+        $ gomplate -i '{{define "T1"}}hello, world!{{end}}{{ tmpl.Exec "T1" | strings.ToUpper }}'
+        HELLO, WORLD!
+      - |
+        $ gomplate -i '{{define "T1"}}hello, {{.}}{{end}}{{ tmpl.Exec "T1" "world!" | strings.Title }}'
+        Hello, World!
   - name: tmpl.Inline
     alias: tpl
     description: |
diff --git a/docs/content/functions/tmpl.md b/docs/content/functions/tmpl.md
index 64a0bf64..f6da5f4d 100644
--- a/docs/content/functions/tmpl.md
+++ b/docs/content/functions/tmpl.md
@@ -7,6 +7,39 @@ menu:
 
 Functions for defining or executing templates.
 
+## `tmpl.Exec`
+
+Execute (render) the named template. This is equivalent to using the [`template`](https://golang.org/pkg/text/template/#hdr-Actions) action, except the result is returned as a string.
+
+This allows for post-processing of templates.
+
+### Usage
+```go
+tmpl.Exec name [context] 
+```
+
+```go
+context | tmpl.Exec name  
+```
+
+### Arguments
+
+| name | description |
+|------|-------------|
+| `name` | _(required)_ The template's name. |
+| `context` | _(optional)_ The context to use. |
+
+### Examples
+
+```console
+$ gomplate -i '{{define "T1"}}hello, world!{{end}}{{ tmpl.Exec "T1" | strings.ToUpper }}'
+HELLO, WORLD!
+```
+```console
+$ gomplate -i '{{define "T1"}}hello, {{.}}{{end}}{{ tmpl.Exec "T1" "world!" | strings.Title }}'
+Hello, World!
+```
+
 ## `tmpl.Inline`
 
 **Alias:** `tpl`
diff --git a/tests/integration/tmpl_test.go b/tests/integration/tmpl_test.go
index ca6e4ad8..3ac2e689 100644
--- a/tests/integration/tmpl_test.go
+++ b/tests/integration/tmpl_test.go
@@ -3,13 +3,42 @@
 package integration
 
 import (
+	"bytes"
+	"io/ioutil"
+	"os"
+
+	"github.com/gotestyourself/gotestyourself/assert"
+	"github.com/gotestyourself/gotestyourself/fs"
+	"github.com/gotestyourself/gotestyourself/icmd"
 	. "gopkg.in/check.v1"
 )
 
-type TmplSuite struct{}
+type TmplSuite struct {
+	tmpDir *fs.Dir
+}
 
 var _ = Suite(&TmplSuite{})
 
+func (s *TmplSuite) SetUpTest(c *C) {
+	s.tmpDir = fs.NewDir(c, "gomplate-tmpltests",
+		fs.WithFiles(map[string]string{
+			"toyaml.tmpl": `{{ . | data.ToYAML }}{{"\n"}}`,
+			"services.yaml": `services:
+  - name: users
+    config:
+      replicas: 2
+  - name: products
+    config:
+      replicas: 18
+`,
+		}),
+	)
+}
+
+func (s *TmplSuite) TearDownTest(c *C) {
+	s.tmpDir.Remove()
+}
+
 func (s *TmplSuite) TestInline(c *C) {
 	inOutTest(c, `
 		{{- $nums := dict "first" 5 "second" 10 }}
@@ -23,3 +52,60 @@ func (s *TmplSuite) TestInline(c *C) {
 		{{- template "T" $othernums }}`,
 		"1510")
 }
+
+func (s *TmplSuite) TestExec(c *C) {
+	result := icmd.RunCmd(icmd.Command(GomplateBin,
+		"-i", `{{ tmpl.Exec "Nope" }}`,
+	))
+	result.Assert(c, icmd.Expected{ExitCode: 1, Err: `template "Nope" not defined`})
+
+	result = icmd.RunCmd(icmd.Command(GomplateBin,
+		"-i", `{{define "T1"}}hello world{{end}}{{ tmpl.Exec "T1" | strings.ToUpper }}`,
+	))
+	result.Assert(c, icmd.Expected{ExitCode: 0, Out: `HELLO WORLD`})
+
+	result = icmd.RunCmd(icmd.Command(GomplateBin,
+		"-c", "in=stdin:///in.json",
+		"-t", "toyaml="+s.tmpDir.Join("toyaml.tmpl"),
+		"-i", `foo:
+{{ tmpl.Exec "toyaml" .in | strings.Indent 2 }}`,
+	), func(cmd *icmd.Cmd) {
+		in := bytes.NewBufferString(`{"a":{"nested": "object"},"b":true}`)
+		cmd.Stdin = in
+	})
+	result.Assert(c, icmd.Expected{ExitCode: 0, Out: `foo:
+  a:
+    nested: object
+  b: true
+`})
+
+	outDir := s.tmpDir.Join("out")
+	err := os.MkdirAll(outDir, 0755)
+	if err != nil {
+		assert.NilError(c, err)
+	}
+	result = icmd.RunCmd(icmd.Command(GomplateBin,
+		"-d", "services="+s.tmpDir.Join("services.yaml"),
+		"-i", `{{- define "config" }}{{ .config | data.ToJSONPretty " " }}{{ end }}
+{{- range (ds "services").services -}}
+{{- $outPath := path.Join .name "config.json" }}
+{{- tmpl.Exec "config" . | file.Write $outPath }}
+{{- end -}}`,
+	), func(cmd *icmd.Cmd) {
+		cmd.Dir = outDir
+	})
+	result.Assert(c, icmd.Expected{ExitCode: 0})
+	assert.Equal(c, "", result.Stdout())
+	assert.Equal(c, "", result.Stderr())
+
+	out, err := ioutil.ReadFile(s.tmpDir.Join("out", "users", "config.json"))
+	assert.NilError(c, err)
+	assert.Equal(c, `{
+ "replicas": 2
+}`, string(out))
+	out, err = ioutil.ReadFile(s.tmpDir.Join("out", "products", "config.json"))
+	assert.NilError(c, err)
+	assert.Equal(c, `{
+ "replicas": 18
+}`, string(out))
+}
diff --git a/tmpl/tmpl.go b/tmpl/tmpl.go
index 59c1a6a0..97ce0fe6 100644
--- a/tmpl/tmpl.go
+++ b/tmpl/tmpl.go
@@ -30,12 +30,33 @@ func (t *Template) Inline(args ...interface{}) (string, error) {
 	if err != nil {
 		return "", err
 	}
+	return t.inline(name, in, ctx)
+}
+
+func (t *Template) inline(name, in string, ctx interface{}) (string, error) {
 	tmpl, err := t.root.New(name).Parse(in)
 	if err != nil {
 		return "", err
 	}
+	return render(tmpl, ctx)
+}
+
+// Exec - execute (render) a template - this is the built-in `template` action, except with output...
+func (t *Template) Exec(name string, context ...interface{}) (string, error) {
+	ctx := t.defaultCtx
+	if len(context) == 1 {
+		ctx = context[0]
+	}
+	tmpl := t.root.Lookup(name)
+	if tmpl == nil {
+		return "", errors.Errorf(`template "%s" not defined`, name)
+	}
+	return render(tmpl, ctx)
+}
+
+func render(tmpl *template.Template, ctx interface{}) (string, error) {
 	out := &bytes.Buffer{}
-	err = tmpl.Execute(out, ctx)
+	err := tmpl.Execute(out, ctx)
 	if err != nil {
 		return "", err
 	}
diff --git a/tmpl/tmpl_test.go b/tmpl/tmpl_test.go
index 0ed21111..729c99fb 100644
--- a/tmpl/tmpl_test.go
+++ b/tmpl/tmpl_test.go
@@ -67,3 +67,24 @@ func TestParseArgs(t *testing.T) {
 	assert.Equal(t, "bar", in)
 	assert.Equal(t, c, ctx)
 }
+
+func TestExec(t *testing.T) {
+	root := template.New("root")
+	t1 := root.New("T1")
+	t1.Parse("hello, {{ . }}")
+	tmpl := &Template{
+		defaultCtx: map[string]string{"foo": "bar"},
+		root:       root,
+	}
+
+	out, err := tmpl.Exec("T1")
+	assert.NoError(t, err)
+	assert.Equal(t, "hello, map[foo:bar]", out)
+
+	out, err = tmpl.Exec("T1", "world")
+	assert.NoError(t, err)
+	assert.Equal(t, "hello, world", out)
+
+	_, err = tmpl.Exec("bogus")
+	assert.Error(t, err)
+}