Drake — a task runner for Deno

Drake is a Make-like task runner for Deno inspired by Make, Rake and Jake.

• Drakefiles (c.f. Makefiles) are Deno TypeScript modules.
• Optional task prerequisites (dependencies).
• File tasks and non-file tasks.
• Drake API functions for defining, registering and running tasks.
• Drake uses conditionally cached file properties to determine whether or not a file task is out of date (see Task Execution). This eliminates the dependency errors that programs such as make encounter when file system mtimes are used directly (see mtime comparison considered harmful).

Status: Tested with Deno 1.40.3 running on Github CI the following platforms: ubuntu-latest, macos-latest, windows-latest. See also the changelog.

Drakefiles

A drakefile is a TypeScript module that:

1. Imports the Drake module.
2. Defines and registers tasks.
3. Runs tasks.

Example drakefile

import { desc, run, task } from "https://deno.land/x/drake@v1.7.0/mod.ts";

desc("Minimal Drake task");
task("hello", [], function () {
  console.log("Hello World!");
});

run();

To run the above example, copy and paste it into a file and run it with Deno. For example:

$ deno run -A minimal-drakefile.ts hello
hello started
Hello World!
hello finished (0ms)

The desc() and task() APIs define and register tasks. The run() API executes the tasks that were specified on the command-line along with their prerequisite tasks. run() is normally the last statement in the drakefile. Tasks are executed in the correct dependency order.

• Use the Drake --help option to list Drake command-line options. For example:

  deno run -A minimal-drakefile.ts --help
  

• By convention, a project's drakefile is named Drakefile.ts and resides in the project's root directory.

Here are some of real-world drakefiles:

• https://github.com/srackham/drake/blob/master/Drakefile.ts
• https://github.com/srackham/rimu/blob/master/Drakefile.ts

Importing Drake

A Drakefile uses Drake APIs imported from the Drake mod.ts module file. The module can be imported from:

• deno.land (Deno's third party modules registry). For example:

  import { desc, run, task } from "https://deno.land/x/drake@v1.7.0/mod.ts";
  

• nest.land (a blockchain based Deno modules registry).
  NOTE: Drake version numbers in nest.land URLs are not prefixed with a 'v' character:

  import { desc, run, task } from "https://x.nest.land/drake@1.7.0/mod.ts";
  

Some Drake APIs are useful in non-drakefiles, use lib.ts (not mod.ts) to import them into non-drakefile modules.

Tasks

Task types

There are two types of task:

Normal task: A normal task executes unconditionally.

File task: A file task is only executed if it is out of date.

Task types are distinguished by their names. Normal task names can only contain alphanumeric, underscore and hyphen characters and cannot start with a hyphen e.g. test, hello-world. File task names are valid file paths. In cases of ambiguity a file task name should be prefixed with a period and a path separator e.g. ./hello-world.

Task properties

name: A unique task name.

desc: An optional task description that is set by the desc() API. Tasks without a description are not displayed by the --list-tasks command-line option (use the -L option to include hidden tasks and task prerequisites in the tasks list).

prereqs: An array of prerequisite task names i.e. the names of tasks to be run prior to executing the task action function. Prerequisites can be normal task names, file task names, file paths or globs (wildcards).

action: An optional function that is run if the task is selected for execution. The action function is bound to the parent task object i.e. the parent task properties are accessible inside the action function through the this object e.g. this.prereqs returns the task's prerequisite names array.

Task execution

Task execution is ordered such that prerequisite tasks (direct and indirect) are executed prior to their parent task. The same task is never run twice.

• The execution directory defaults to the current working directory (this can be changed using the Drake --directory command-line option).

• Task name and prerequisite file paths are normalized at task registration.

• Prerequisite globs are expanded when the task is registered.

• Prerequisites are resolved at the time the task is run.

• All prerequisite files must exist by the time the task executes. An error is thrown if any are missing.

• A file task is considered to be out of date if:

  • The target file does not exist.
  • The target file or any of the prerequisite files have changed since the task was last executed successfully.
  • The Drake version or the operating system has changed since the task was last executed successfully.

• A file is considered to have changed if it's current modification time or size no longer matches those recorded immediately after the task last executed successfully.

• Before exiting Drake saves the target and prerequisite file properties of the tasks that successfully executed:

  • File properties are saved to a file named .drake.cache.json in the drakefile execution directory (this file path can be changed using the Drake --cache command-line option).
  • Task target and prerequisite file properties are recorded immediately after successful task execution (if a task fails its properties are not updated).
  • A cache file will not be created until at least one file task has successfully executed.

Asynchronous task actions

Normally you will want tasks to execute sequentially i.e. the next task should not start until the current task has finished. To ensure this happens action functions that call asynchronous functions should:

1. Be declared async.
2. Call asynchronous functions with the await operator.

For example, the following task does not return until the shell command has successfully executed:

task("shell", [], async function () {
  await sh("echo Hello World");
});

Without the await operator sh("echo Hello World") will return immediately and the action function will exit before the shell command has even started.

Of course you are free to eschew await and use the promises returned by asynchronous functions in any way that makes sense.

Drakefile execution

A drakefile is executed from the command-line. Use the --help option to view Drake command-line options and syntax. For example:

$ deno run -A Drakefile.ts --help

NAME
  drake - a make-like task runner for Deno.

SYNOPSIS
  deno run -A DRAKEFILE [OPTION|VARIABLE|TASK]...

DESCRIPTION
  The Drake TypeScript module provides functions for defining and executing
  build TASKs on the Deno runtime.

  A DRAKEFILE is a TypeScript module file containing Drake task definitions.
  Drakefiles are run with the Deno 'run' command.

  A Drake VARIABLE is a named string value e.g. 'vers=0.1.0'.  Variables are
  accessed using the Drake 'env' API e.g. 'env("vers").

OPTIONS
  -a, --always-make     Unconditionally execute tasks.
  --cache FILE          Set Drake cache file path to FILE.
  -d, --directory DIR   Change to directory DIR before running drakefile.
  -D, --debug           Write debug information to stderr.
  -h, --help            Display this help message.
  -l, -L, --list-tasks  List tasks (-L for hidden tasks and prerequisites).
  -n, --dry-run         Skip task execution.
  -q, --quiet           Do not log drake messages to standard output.
  -v, --verbose         Increase verbosity.
  --version             Display the drake version.

ENVIRONMENT VARIABLES
  NO_COLOR              Set to disable color (see https://no-color.org/).

SEE ALSO
  The Drake user guide: https://github.com/srackham/drake

The --directory option sets the drakefile execution directory and defaults to the current working directory. The --directory option allows a single drakefile to be used to build multiple project directories.

If no command-line tasks are given the default task is run (specified by setting the env API "--default-task" value).

A Drake command-line variable is a named string value that is made available to the drakefile. Variables are formatted like <name>=<value> e.g. vers=0.1.0. Variables are accessed within a drakefile using the env API e.g. env("vers"). Variable names can only contain alphanumeric or underscore characters and must start with an alpha character.

Drake API

The Drake library module exports the following functions:

abort

function abort(message: string): void;

Write an error message to stderr and terminate execution.

• If the "--abort-exits" environment option is false throw a DrakeError.
• If the "--debug" environment option is true include the stack trace in the error message.

debug

function debug(title: string, message?: any): void;

Write the title and message to stderr if it is a TTY and the --debug command-line option was specified or the DRAKE_DEBUG shell environment variable is set.

desc

function desc(description: string): void;

Set description of next registered task. If a task has no description then it won't be displayed in the tasks list unless the -L option is used.

env

function env(name?: string, value?: EnvValue): any;

The Drake env API function gets and optionally sets the command-line options, task names and variables.

Options are