Add support for derived variables #79

examples/derived/template.toml

@@ -0,0 +1,15 @@
+name = "Java domain"
+description = "Dynamic folder structure"
+kickstart_version = 1
+
+[[variables]]
+name = "package"
+default = "my.domain.test"
+prompt = "Enter your package name (dot-separated):"
+validation = "^[a-z]+(\\.[a-z][a-z0-9_]*)*$"
+
+[[variables]]
+name = "package_path"
+default = "{{ package | replace(from='.', to='/')}}"
+prompt = "Will not be asked since this is a derived variable"
+derived = true

examples/derived/{{package_path}}/Main.java

@@ -0,0 +1,7 @@
+package {{package}};
+
+public class Main {
+    public static void main(String[] args) {
+        System.out.println("Hello, World!");
+    }
+}

src/definition.rs

@@ -42,6 +42,8 @@ pub struct Variable {
     pub validation: Option<String>,
     /// Only ask this variable if that condition is true
     pub only_if: Option<Condition>,
+    /// Whether this variable is derived and should not be prompted
+    pub derived: Option<bool>,
 }
 
 /// A hook is a file that will get executed
@@ -421,4 +423,41 @@ mod tests {
 
         assert_eq!(got_value, &Value::String(expected_value))
     }
+
+    #[test]
+    fn can_handle_derived_variable_with_no_input() {
+        let tpl: TemplateDefinition = toml::from_str(
+            r#"
+        name = "Test template"
+        description = "Testing derived variable behavior"
+        kickstart_version = 1
+
+        [[variables]]
+        name = "project_name"
+        default = "My project"
+        prompt = "What's the name of your project?"
+
+        [[variables]]
+        name = "slug"
+        default = "{{project_name | slugify}}"
+        prompt = "Slug for the project"
+        derived = true
+        "#,
+        )
+        .unwrap();
+
+        assert_eq!(tpl.variables.len(), 2);
+
+        let res = tpl.default_values();
+        assert!(res.is_ok());
+        let res = res.unwrap();
+
+        // Check that both variables exist
+        assert!(res.contains_key("project_name"));
+        assert!(res.contains_key("slug"));
+
+        // Check that slug was rendered from project_name
+        let expected_slug = Value::String("my-project".to_string());
+        assert_eq!(res.get("slug"), Some(&expected_slug));
+    }
 }

src/main.rs

@@ -54,6 +54,12 @@ fn ask_questions(template: &Template, no_input: bool) -> Result<HashMap<String,
     let mut vals = HashMap::new();
 
     for var in &template.definition.variables {
+        if var.derived.unwrap_or(false) {
+            let default = template.get_default_for(&var.name, &vals)?;
+            vals.insert(var.name.clone(), default);
+            continue;
+        }
+
         if !template.should_ask_variable(&var.name, &vals)? {
             continue;
         }