Add support for custom placeholders

Signed-off-by: Mathieu Frenette <silphid@users.noreply.github.com>

Author: silphid

.prettierrc.yaml

@@ -0,0 +1,4 @@
+overrides:
+  - files: "*.yaml"
+    options:
+      bracketSpacing: false

README.md

@@ -448,11 +448,18 @@ As the conditional for `if` steps is always a template expression, _do not_ encl
 
 ## Special placeholders
 
-Because the PROJECT variable is typically used pervasively throughout templates in the form of `{{.PROJECT}}` and `{{.PROJECT | upper}}`, we have introduced the special placeholders `projekt` and `PROJEKT`, which can be used anywhere in file/dir names and templates without any adornments.
+Placeholders are a lightweight alternative to go template expressions, which can be used as plain text anywhere in file/dir names and template files. Because placeholders are processed using plain search-and-replace, ensure they have improbable names that don't risk conflicting with anything else (ie: "projekt").
 
-For example, the text "MY PROJEKT FILE.TXT" is equivalent to "MY {{.PROJECT | upper}} FILE.TXT".
+For example, you can define the following placeholders in your template spec:
 
-Currently, those two placeholders are hardcoded and are the only ones supported, but we plan to add support for defining your own in the template spec.
+```yaml
+placeholders:
+  projekt: "{{ .PROJECT | lower }}"
+  Projekt: "{{ .PROJECT | title }}"
+  PROJEKT: "{{ .PROJECT | upper }}"
+```
+
+You can then use these placeholders anywhere without any adornments. For example, the text "MY PROJEKT FILE.TXT" is equivalent to "MY {{.PROJECT | upper}} FILE.TXT".
 
 This feature was inspired by the way we were previously creating new projects by duplicating an existing project and doing a search-and-replace for the project name in different case variants. That strategy was very simple and effective, as long as the project name was a very distinct string that did not appear in any other undesired contexts, hence our choice of `projekt` as something that you are (hopefully!) very
 unlikely to encounter in your project for any other reason than those placeholders!
@@ -486,10 +493,3 @@ To associate a template with an existing project that was not initially generate
 - Add more example templates, for go, node...
 - Fix `choice` step to pre-select current value, if any.
 - Allow special `.tmpl` and `.notmpl` extensions to be placed before actual extension (ie: `file.tmpl.txt`), to allow file editor to recognize them better during template editing.
-- Allow to customize placeholders in spec file:
-
-```
-placeholders:
-  projekt: {{.PROJECT | lower}}
-  PROJEKT: {{.PROJECT | upper}},
-```

examples/.prettierrc.yaml

@@ -0,0 +1,4 @@
+overrides:
+  - files: "*.yaml"
+    options:
+      bracketSpacing: false

examples/templates/hello-world/spec.yaml

@@ -4,6 +4,15 @@ version: 0.2.0
 # Description displayed to user during template selection
 description: The customary Hello World example
 
+# Placeholders are a lightweight alternative to go template expressions, which can be used as
+# plain text anywhere in file/dir names and template files. Because placeholders are processed
+# using plain search-and-replace, ensure they have improbable names that don't risk conflicting
+# with anything else (ie: "projekt").
+placeholders:
+  projekt: "{{.PROJECT | lower}}"
+  Projekt: "{{.PROJECT | title}}"
+  PROJEKT: "{{.PROJECT | upper}}"
+
 # Actions are sets of steps that can be invoked by user by their name
 actions:
   # By convention, the "create" action is in charge of scaffolding the project initially

examples/templates/hello-world/src/README.md.tmpl

@@ -2,11 +2,12 @@
 
 The PROJEKT project is managed by the {{.TEAM}} team.
 
-`PROJEKT` is a special placeholder equivalent to {{.PROJECT | upper}}
+The `PROJEKT` placeholder is defined in spec as equivalent to {{.PROJECT | upper}}
 
 Project name: {{.PROJECT}}
 Project name in uppercase: {{.PROJECT | upper}}
 Placeholder lowercase: projekt
+Placeholder titlecase: Projekt
 Placeholder uppercase: PROJEKT
 
 It was created with:

src/cmd/internal/internal.go

@@ -97,19 +97,10 @@ func (c context) IsVarOverriden(name string) bool {
 }
 
 // GetPlaceholders returns a map of special placeholders that can be used instead
-// of go template expression, for lighter weight templating, especially for the
-// project's name, which appears everywhere. For now, the only supported placeholder
-// is PROJECT, but we will eventually make placeholders configurable in spec file.
+// of go template expressions, for more lightweight templating, especially for the
+// project's name, which appears everywhere.
 func (c context) GetPlaceholders() map[string]string {
-	value, _ := c.project.Vars["PROJECT"]
-	str, ok := value.(string)
-	if !ok {
-		return nil
-	}
-	return map[string]string{
-		"projekt": strings.ToLower(str),
-		"PROJEKT": strings.ToUpper(str),
-	}
+	return c.spec.Placeholders
 }
 
 // GetEvalVars returns a dictionary of the project's variable names mapped to

src/internal/evaluation/evaluation.go

@@ -18,7 +18,7 @@ type Context interface {
 	GetEvalVars() map[string]interface{}
 
 	// GetPlaceholders returns a map of special placeholders that can be used instead
-	// of go template expression, for lighter weight templating, especially for the
+	// of go template expressions, for more lightweight templating, especially for the
 	// project's name, which appears everywhere.
 	GetPlaceholders() map[string]string
 
@@ -64,8 +64,8 @@ func EvalTemplate(context Context, text string) (string, error) {
 	text = strings.ReplaceAll(text, tripleClose, doubleOpen+"`"+doubleClose+"`"+doubleClose)
 
 	// Perform replacement of placeholders
-	for search, replace := range context.GetPlaceholders() {
-		text = strings.ReplaceAll(text, search, replace)
+	for placeholderName, placeholderValue := range context.GetPlaceholders() {
+		text = strings.ReplaceAll(text, placeholderName, placeholderValue)
 	}
 
 	// Render go template

src/internal/exec/exec.go

@@ -17,7 +17,7 @@ type Context interface {
 	IsVarOverriden(name string) bool
 
 	// GetPlaceholders returns a map of special placeholders that can be used instead
-	// of go template expression, for lighter weight templating, especially for the
+	// of go template expressions, for more lightweight templating, especially for the
 	// project's name, which appears everywhere.
 	GetPlaceholders() map[string]string
 

src/internal/spec/spec.go

@@ -19,10 +19,11 @@ import (
 
 // Spec represents a template specification file found in the root of the template's dir
 type Spec struct {
-	Name        string
-	Version     string
-	Description string
-	Actions     map[string]Action
+	Name         string
+	Version      string
+	Description  string
+	Placeholders map[string]string
+	Actions      map[string]Action
 }
 
 // Load loads spec object from a template directory
@@ -58,6 +59,15 @@ func loadFromMap(_map yaml.Map, templateDir string) (*Spec, error) {
 		return nil, err
 	}
 
+	// Load placeholders
+	placeholders, ok, err := getOptionalMap(_map, "placeholders")
+	if err != nil {
+		return nil, err
+	}
+	if ok {
+		spec.Placeholders, err = loadPlaceholders(placeholders)
+	}
+
 	// Load actions
 	actions, err := getRequiredMap(_map, "actions")
 	if err != nil {
@@ -71,6 +81,18 @@ func loadFromMap(_map yaml.Map, templateDir string) (*Spec, error) {
 	return spec, nil
 }
 
+func loadPlaceholders(_map yaml.Map) (map[string]string, error) {
+	placeholders := make(map[string]string, len(_map))
+	for key, node := range _map {
+		value, ok := getString(node)
+		if !ok {
+			return nil, fmt.Errorf("value for placeholder %q must be a string", key)
+		}
+		placeholders[key] = value
+	}
+	return placeholders, nil
+}
+
 func loadActions(node yaml.Map, templateDir string) (ActionMap, error) {
 	var actions []Action
 	for name, value := range node {

src/internal/spec/spec_test.go

@@ -364,9 +364,10 @@ func TestLoadSpec(t *testing.T) {
 			Buffer: `
 version: 0.2.0
 description: Description
-import:
-  common: common
-  go: go/common
+placeholders:
+  projekt: {{.PROJECT | lower}}
+  Projekt: {{.PROJECT | title}}
+  PROJEKT: {{.PROJECT | upper}}
 actions:
   action1:
     - if: Condition 1
@@ -382,6 +383,11 @@ actions:
 				Name:        "template_name",
 				Version:     "0.2.0",
 				Description: "Description",
+				Placeholders: map[string]string{
+					"projekt": "{{.PROJECT | lower}}",
+					"Projekt": "{{.PROJECT | title}}",
+					"PROJEKT": "{{.PROJECT | upper}}",
+				},
 				Actions: ActionMap{
 					"action1": Action{
 						Name: "action1",