Allow sourcing prompt answers from env variables (#14)

Fixes #12

Co-authored-by: jolheiser <john.olheiser@gmail.com>
Reviewed-on: https://gitea.com/jolheiser/tmpl/pulls/14
Co-authored-by: John Olheiser <john.olheiser@gmail.com>
Co-committed-by: John Olheiser <john.olheiser@gmail.com>

DOCS.md

@@ -15,6 +15,10 @@ A "valid" tmpl template only requires two things
 The template.toml file will only expand environment variables with syntax `$USER` or `${USER}`.  
 For full documentation on the syntax, see [os.ExpandEnv](https://golang.org/pkg/os/#ExpandEnv).
 
+When using the `--defaults` flag, no prompts will be shown and only default values will be used.  
+As another alternative, any environment variable that matches a key will bypass the prompt.  
+For example, `author` would have the corresponding environment variable `TMPL_VAR_AUTHOR`.
+
 ```toml
 # Key-value pairs can be simple
 # The user will receive a basic prompt asking them to fill out the variable

registry/prompt.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"path/filepath"
 	"sort"
+	"strings"
 	"text/template"
 
 	"github.com/AlecAivazis/survey/v2"
@@ -67,15 +68,22 @@ func prompt(dir string, defaults bool) (templatePrompts, error) {
 		prompts[idx] = p
 	}
 
-	// Return early if we only want defaults
-	if defaults {
-		return prompts, nil
-	}
-
 	// Sort the prompts so they are consistent
 	sort.Sort(prompts)
 
 	for idx, prompt := range prompts {
+		// Check for env variable
+		if e, ok := os.LookupEnv(fmt.Sprintf("TMPL_VAR_%s", strings.ToUpper(prompt.Key))); ok {
+			prompts[idx].Value = e
+			continue
+		}
+
+		// Check if we are using defaults
+		if defaults {
+			prompts[idx].Value = prompt.Default
+			continue
+		}
+
 		var p survey.Prompt
 		switch t := prompt.Default.(type) {
 		case []string:
@@ -119,11 +127,7 @@ type templatePrompts []templatePrompt
 func (t templatePrompts) ToMap() map[string]interface{} {
 	m := make(map[string]interface{})
 	for _, p := range t {
-		if p.Value != nil {
-			m[p.Key] = p.Value
-			continue
-		}
-		m[p.Key] = p.Default
+		m[p.Key] = p.Value
 	}
 	return m
 }

registry/registry_test.go

@@ -17,7 +17,7 @@ var (
 
 func TestMain(m *testing.M) {
 	var err error
-	destDir, err = ioutil.TempDir(os.TempDir(), "tmpl")
+	destDir, err = ioutil.TempDir(os.TempDir(), "tmpl-dest")
 	if err != nil {
 		panic(err)
 	}
@@ -75,7 +75,7 @@ func testGetFail(t *testing.T) {
 
 func setupTemplate() {
 	var err error
-	tmplDir, err = ioutil.TempDir(os.TempDir(), "tmpl")
+	tmplDir, err = ioutil.TempDir(os.TempDir(), "tmpl-setup")
 	if err != nil {
 		panic(err)
 	}
@@ -122,7 +122,7 @@ func setupTemplate() {
 
 func setupRegistry() {
 	var err error
-	regDir, err = ioutil.TempDir(os.TempDir(), "tmpl")
+	regDir, err = ioutil.TempDir(os.TempDir(), "tmpl-reg")
 	if err != nil {
 		panic(err)
 	}

registry/template.go

@@ -67,7 +67,7 @@ func (t *Template) Execute(dest string, defaults, overwrite bool) error {
 			return err
 		}
 
-		newDest := strings.TrimPrefix(walkPath, base+"/")
+		newDest := strings.TrimPrefix(walkPath, base+string(filepath.Separator))
 		newDest = filepath.Join(dest, newDest)
 
 		tmplDest, err := template.New("dest").Funcs(funcs).Parse(newDest)

registry/template_test.go

@@ -8,7 +8,7 @@ import (
 )
 
 var (
-	tmplContents = `{{title name}} {{if .bool}}{{.year}}{{end}}`
+	tmplContents = `{{title name}} (@{{username}}) {{if .bool}}{{.year}}{{end}}`
 	tmplTemplate = `
 name = "john olheiser"
 
@@ -20,8 +20,11 @@ default = "pkg"
 
 [bool]
 default = true
+
+[username]
+default = "username"
 `
-	tmplGold    = "John Olheiser 2020"
+	tmplGold    = "John Olheiser (@jolheiser) 2020"
 	tmplNewGold = "DO NOT OVERWRITE!"
 )
 
@@ -31,6 +34,10 @@ func testExecute(t *testing.T) {
 		t.Logf("could not set environment: %v", err)
 		t.FailNow()
 	}
+	if err := os.Setenv("TMPL_VAR_USERNAME", "jolheiser"); err != nil {
+		t.Logf("could not set environment: %v", err)
+		t.FailNow()
+	}
 
 	// Get template
 	tmpl, err := reg.GetTemplate("test")