Merge pull request #673 from marwan-at-work/tpl

codegen/templates: allow templates to be passed in options instead of…

codegen/templates/templates.go

@@ -19,18 +19,36 @@ import (
 	"github.com/pkg/errors"
 )
 
+// CurrentImports keeps track of all the import declarations that are needed during the execution of a plugin.
 // this is done with a global because subtemplates currently get called in functions. Lets aim to remove this eventually.
 var CurrentImports *Imports
 
+// Options specify various parameters to rendering a template.
 type Options struct {
-	PackageName     string
+	// PackageName is a helper that specifies the package header declaration.
+	// In other words, when you write the template you don't need to specify `package X`
+	// at the top of the file. By providing PackageName in the Options, the Render
+	// function will do that for you.
+	PackageName string
+	// Template is a string of the entire template that
+	// will be parsed and rendered. If it's empty,
+	// the plugin processor will look for .gotpl files
+	// in the same directory of where you wrote the plugin.
+	Template string
+	// Filename is the name of the file that will be
+	// written to the system disk once the template is rendered.
 	Filename        string
 	RegionTags      bool
 	GeneratedHeader bool
-	Data            interface{}
-	Funcs           template.FuncMap
+	// Data will be passed to the template execution.
+	Data  interface{}
+	Funcs template.FuncMap
 }
 
+// Render renders a gql plugin template from the given Options. Render is an
+// abstraction of the text/template package that makes it easier to write gqlgen
+// plugins. If Options.Template is empty, the Render function will look for `.gotpl`
+// files inside the directory where you wrote the plugin.
 func Render(cfg Options) error {
 	if CurrentImports != nil {
 		panic(fmt.Errorf("recursive or concurrent call to RenderToFile detected"))
@@ -48,31 +66,40 @@ func Render(cfg Options) error {
 	t := template.New("").Funcs(funcs)
 
 	var roots []string
-	// load all the templates in the directory
-	err := filepath.Walk(rootDir, func(path string, info os.FileInfo, err error) error {
+	if cfg.Template != "" {
+		var err error
+		t, err = t.New("template.gotpl").Parse(cfg.Template)
 		if err != nil {
-			return err
-		}
-		name := filepath.ToSlash(strings.TrimPrefix(path, rootDir+string(os.PathSeparator)))
-		if !strings.HasSuffix(info.Name(), ".gotpl") {
-			return nil
-		}
-		b, err := ioutil.ReadFile(path)
-		if err != nil {
-			return err
+			return errors.Wrap(err, "error with provided template")
 		}
+		roots = append(roots, "template.gotpl")
+	} else {
+		// load all the templates in the directory
+		err := filepath.Walk(rootDir, func(path string, info os.FileInfo, err error) error {
+			if err != nil {
+				return err
+			}
+			name := filepath.ToSlash(strings.TrimPrefix(path, rootDir+string(os.PathSeparator)))
+			if !strings.HasSuffix(info.Name(), ".gotpl") {
+				return nil
+			}
+			b, err := ioutil.ReadFile(path)
+			if err != nil {
+				return err
+			}
 
-		t, err = t.New(name).Parse(string(b))
-		if err != nil {
-			return errors.Wrap(err, cfg.Filename)
-		}
+			t, err = t.New(name).Parse(string(b))
+			if err != nil {
+				return errors.Wrap(err, cfg.Filename)
+			}
 
-		roots = append(roots, name)
+			roots = append(roots, name)
 
-		return nil
-	})
-	if err != nil {
-		return errors.Wrap(err, "locating templates")
+			return nil
+		})
+		if err != nil {
+			return errors.Wrap(err, "locating templates")
+		}
 	}
 
 	// then execute all the important looking ones in order, adding them to the same file
@@ -91,7 +118,7 @@ func Render(cfg Options) error {
 		if cfg.RegionTags {
 			buf.WriteString("\n// region    " + center(70, "*", " "+root+" ") + "\n")
 		}
-		err = t.Lookup(root).Execute(&buf, cfg.Data)
+		err := t.Lookup(root).Execute(&buf, cfg.Data)
 		if err != nil {
 			return errors.Wrap(err, root)
 		}
@@ -110,7 +137,7 @@ func Render(cfg Options) error {
 	result.WriteString("import (\n")
 	result.WriteString(CurrentImports.String())
 	result.WriteString(")\n")
-	_, err = buf.WriteTo(&result)
+	_, err := buf.WriteTo(&result)
 	if err != nil {
 		return err
 	}

codegen/templates/templates_test.go

@@ -1,6 +1,8 @@
 package templates
 
 import (
+	"io/ioutil"
+	"os"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -100,3 +102,16 @@ func TestCenter(t *testing.T) {
 	require.Equal(t, "##fffff###", center(10, "#", "fffff"))
 	require.Equal(t, "###fffff###", center(11, "#", "fffff"))
 }
+
+func TestTemplateOverride(t *testing.T) {
+	f, err := ioutil.TempFile("", "gqlgen")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+	defer os.RemoveAll(f.Name())
+	err = Render(Options{Template: "hello", Filename: f.Name()})
+	if err != nil {
+		t.Fatal(err)
+	}
+}