> For the complete documentation index, see [llms.txt](https://no0dles.gitbook.io/hammerkit/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://no0dles.gitbook.io/hammerkit/task/extending.md).

# Extending

Extending tasks can save a lot of duplicated tasks in bigger projects and monorepos. With the task `extend` property a base configuration can be used as a template.

The following sections and examples use the two predefined tasks in the `build.tsc.yaml` file — one of the ready-made templates shipped under [`best-practices/`](/hammerkit/recipes.md). Copy it into your project (or include it directly) to follow along.

{% code title="build.tsc.yaml" %}

```yaml
tasks:
  install:
    src:
      - package.json
      - package-lock.json
    generates:
      - node_modules
    cmds:
      - npm ci
      
  build:
    deps: [ install ]
    src:
      - tsconfig.json
      - src
    cmds:
      - node_modules/.bin/tsc
    generates:
      - dist
```

{% endcode %}

### Extend a task

Extending the `tsc:build` task will use all defined properties as a base. If nothing else is defined, it will be an exact copy with the working directory of the current build file.

{% code title=".hammerkit.yaml" %}

```yaml
tasks:
  build:
    extend: tsc:build
    
includes:
  tsc: ./build.tsc.yaml
```

{% endcode %}

### Override properties in an extend

Every extended task can override defined or undefined properties. In this example the dependency gets cleared and runs without a dependency to the `install` task.

{% code title=".hammerkit.yaml" %}

```yaml
tasks:
  build:
    extend: tsc:build
    deps: []
    
includes:
  tsc: ./build.tsc.yaml
```

{% endcode %}

### Naming the base task

`extend` uses the same `<prefix>:<task>` addressing as [dependencies](/hammerkit/task/dependencies.md): the part before the colon is the [include](/hammerkit/build-file/includes.md) (or [reference](/hammerkit/build-file/references.md)) prefix, and the part after it is the task name in that file. `extend: tsc:build` means "the `build` task from the file included as `tsc`". To extend a task in the *same* file, use its bare name (`extend: build-base`).


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