Handle substitution for templates

Author: stuartleeks

docs/template.md

@@ -82,11 +82,20 @@ Assuming you cloned [github.com/microsoft/vscode-dev-containers/](https://github
 }
 ```
 
+## Placeholder Values
+
+After content has been copied to the project folder from a template, the following placeholder values are substituted:
+
+| Placeholder                  | Value                                                                                                                |
+|------------------------------|----------------------------------------------------------------------------------------------------------------------|
+| `__DEVCONTAINER_NAME__`      | The name of the dev container (from the `name` property in `devcontainer.json`)                                      |
+| `__DEVCONTAINER_USER_NAME__` | The name of the user for dev container (from the `remoteuser` property in `devcontainer.json`, or `root` if not set) |
+| `__DEVCONTAINER_HOME__`      | The home folder for the dev container (e.g. `/home/vscode` or `/root`)                                               |
+
 ## Repository containers
 
 VS Code dev containers have another feature called "Repository containers". These are a set of dev container definitions that VS Code will automatically apply to a project based on its git repo.
 
 The default definitions are in the [microsoft/vscode-dev-containers](https://github.com/microsoft/vscode-dev-containers/tree/master/repository-containers) repo. If you look at the repo, you will see a `github.com` folder followed by paths for `<org>/<repo>`, e.g. `django/django`. The `https://github.com/django/django` repo doesn't contain a dev container definition, but VS Code will use the repository container definition from the `microsoft/vscode-dev-containers` repo.
 
-You can also configure VS Code to look for additional local paths for repository containers by providing a value for the VS Code `remote.containers.repository-container-paths` setting (see [this issue](https://github.com/microsoft/vscode-remote-release/issues/3218) for more details). 
-
+You can also configure VS Code to look for additional local paths for repository containers by providing a value for the VS Code `remote.containers.repository-container-paths` setting (see [this issue](https://github.com/microsoft/vscode-remote-release/issues/3218) for more details).

internal/pkg/devcontainers/snippet.go

@@ -407,6 +407,17 @@ func getSubstitutionValuesFromFile(devContainerJsonPath string) (*SubstitutionVa
 	}, nil
 }
 
+func performSubstitutionFile(substitutionValues *SubstitutionValues, filename string) error {
+	buf, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return err
+	}
+	content := string(buf)
+	content = performSubstitutionString(substitutionValues, content)
+	err = ioutil.WriteFile(filename, []byte(content), 0)
+	return err
+}
+
 func performSubstitutionString(substitutionValues *SubstitutionValues, content string) string {
 	// replace __DEVCONTAINER_NAME__ with name etc
 	content = strings.ReplaceAll(content, "__DEVCONTAINER_NAME__", substitutionValues.Name)

internal/pkg/devcontainers/template.go

@@ -113,7 +113,7 @@ func GetDefaultDevcontainerNameForFolder(folderPath string) (string, error) {
 func CopyTemplateToFolder(templatePath string, targetFolder string, devcontainerName string) error {
 	var err error
 
-	if err = ioutil2.CopyFolder(templatePath, targetFolder+"/.devcontainer"); err != nil {
+	if err = ioutil2.CopyFolder(templatePath, filepath.Join(targetFolder, ".devcontainer")); err != nil {
 		return fmt.Errorf("Error copying folder: %s\n", err)
 	}
 
@@ -125,12 +125,46 @@ func CopyTemplateToFolder(templatePath string, targetFolder string, devcontainer
 			return fmt.Errorf("Error getting default devcontainer name: %s", err)
 		}
 	}
-	devcontainerJsonPath := filepath.Join(targetFolder, ".devcontainer/devcontainer.json")
+	devcontainerJsonPath := filepath.Join(targetFolder, ".devcontainer", "devcontainer.json")
 	err = SetDevcontainerName(devcontainerJsonPath, devcontainerName)
 	if err != nil {
 		return fmt.Errorf("Error setting devcontainer name: %s", err)
 	}
 
+	values, err := getSubstitutionValuesFromFile(devcontainerJsonPath)
+	if err != nil {
+		return fmt.Errorf("Error getting substituion values: %s", err)
+	}
+	err = recursiveSubstituteValues(values, filepath.Join(targetFolder, ".devcontainer"))
+	if err != nil {
+		return fmt.Errorf("Error performing substitution: %s", err)
+	}
+
+	return nil
+}
+
+func recursiveSubstituteValues(values *SubstitutionValues, path string) error {
+	_, err := os.Stat(path)
+	if err != nil {
+		return fmt.Errorf("Error reading folder: %s\n", err)
+	}
+
+	subItems, err := ioutil.ReadDir(path)
+	if err != nil {
+		return fmt.Errorf("Error reading source folder contents: %s\n", err)
+	}
+
+	for _, subItem := range subItems {
+		if subItem.IsDir() {
+			if err = recursiveSubstituteValues(values, filepath.Join(path, subItem.Name())); err != nil {
+				return err
+			}
+		} else {
+			if err = performSubstitutionFile(values, filepath.Join(path, subItem.Name())); err != nil {
+				return err
+			}
+		}
+	}
 	return nil
 }