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.

Status: Tested with Deno 1.4.1 running on Ubuntu 20.04, Windows 10. See the changelog.

Drakefiles

A drakefile is a TypeScript module that:

Imports the Drake module.
Defines and registers tasks.
Runs tasks.

Example drakefile

import { desc, run, task } from "https://deno.land/x/drake@v1.4.1/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:

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@v1.4.1/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@1.4.1/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File task: A File task is only executed if it is out of date.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.

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 had last executed successfully.
The execution directory defaults to the current working directory and can be changed using the Drake --directory command-line option.
Drake saves target and prerequisite file properties to a file named .drake.cache.json in the drakefile execution directory. A .drake.cache.json file will not be created until a 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:

Be declared async.
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.
  --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.

Tips for using Drake

A shell alias shortcut can be set to run the default drakefile:
```
alias drake="deno run -A Drakefile.ts"
```
Use shell quoting and escapes to pass Drake command-line variable values that contain spaces or special characters e.g. "title=Foo & bar".
Don’t forget to use await when calling async functions.
Task path name prerequisites can be glob wildcards.
Task name and prerequisite file paths can refer to any file type (not just regular files).
The Drake sh API can be used to run multiple shell commands asynchronously. The following example starts two shell commands then waits for both to finish before continuing:
```
  await sh(["echo foo", "echo bar"]);
```

The Drake sh API can be used to run multi-line template string scripts e.g.

await sh(`set -e  # Exit immediately on error.
    echo Hello World
    if [ "$EUID" -eq 0 ]; then
        echo "Running as root"
    else
        echo "Running as $USER"
    fi
    ls
    wc Drakefile.ts`);

Escape backslash and backtick characters and placeholders in template string literals with a backslash:
- \\ translates to \
- \` translates to `
- \${ translates to ${

Tasks can be created dynamically at runtime. The following example is from examples/dynamic-tasks.ts:

for (const prereq of glob("*.md")) {
  const target = `${path.basename(prereq, ".md")}.html`;
  task(target, [prereq], async function () {
    await sh(`markdown "${prereq}" > "${target}"`);
  });
}

Task actions can be run asynchronously using the execute API. The following example is from examples/dynamic-tasks.ts:
```
await execute(...tasks);  // 'tasks' is a list of tasks with asynchronous action functions.
```
When running multiple tasks asynchronously, for example using the execute API, take care that there are no mutual dependencies that could cause race conditions.
More meaningful file task names can be created with a dummy normal task. In the following example the build-docs task executes the ./docs/index.html task. The ./docs/index.html task will be hidden from the --list-tasks command because it has not been assigned a description.
```
desc("Build documents");
task("build-docs", ["./docs/index.html]);
task("./docs/index.html", [...]) {
  ...
});
```
When executing in a drakefile, Drake functions manifest errors by printing an error message and exiting with a non-zero exit code. You can change this behavior so that errors throw a DrakeError exception by setting env("--abort-exits", false). In non-drakefiles errors throw a DrakeError exception by default.
Selected sections of code can be “debugged” by bracketing with env("--debug",true) and env("--debug",false) statements.
Drake API debug messages will be emitted if the DRAKE_DEBUG shell environment variable is set. This can be useful in conjunction with the debug API in non-drakefiles (in lieu of the Drake --debug command-line option).
The Deno run command automatically compiles updated source and writes compilation messages to stderr. This can interfere with tests that capture Deno run command outputs. Use the Deno --quiet option to eliminate this problem.
In addition to the command-line --cache FILE option you can also set a custom cache file path from within a Drakefile before calling the run API. For example:
```
env("--cache", path.join(env("--directory"), "my-cache.json"));
```
Set the --cache option value to a blank string to restore the default cache file path:
```
env("--cache", "");
```

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 true 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 keyed by their long option name e.g. env("--dry-run"). Command-line flag options return a boolean; the --cache and --directory options return a string.

Command-line variables are keyed by name. For example vers=1.0.1 on the command-line sets the vers value to "1.0.1".

Command-line tasks are stored in the --tasks string array.

Examples:

env("--abort-exits", true);
env("--default-task", "test");
console.log(`version: ${env("vers")}`);
if (!env("--quiet")) console.log(message);

execute

async function execute(...taskNames: string[]);

Execute task action functions. First the non-async actions are executed synchronously then the async actions are exectuted asynchronously. Silently skip tasks that have no action function.

glob

function glob(...patterns: string[]): string[];

Return a sorted array of normalized file names matching the wildcard patterns. Valid glob patterns are those supported by Deno’s path library Example: glob("tmp/*.ts", "lib/**/*.ts", "mod.ts");

log

function log(message: string): void;

Log a message to stdout. Do not log the message if the --quiet command-line option is set.

makeDir

function makeDir(dir: string): boolean;

Create directory.

Missing parent directory paths are created.
Returns true if a new directory was created.
Returns false if the directory already exists.

quote

function quote(values: string[], sep: string = " "): string;

Quote string array values with double-quotes then join them with a separator. Double-quote characters are escaped with a backspace. The separator defaults to a space character.

readFile

function readFile(filename: string): string;

Read the entire contents of a file synchronously to a UTF-8 string.

run

async function run(...taskNames: string[]);

Execute named tasks along with their prerequisite tasks (direct and indirect). If no task names are specified then the command-line tasks are run. If no command-line tasks were specified the default task is run (specified by setting the env API "--default-task" value).

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

sh

async function sh(commands: string | string[], opts: ShOpts = {});

Execute commands in the command shell.

If commands is a string execute it.
If commands is an array of commands execute them asynchronously.
If any command fails throw an error.
If opts.stdout or opts.stderr is set to "null" then the respective outputs are suppressed.
opts.cwd sets the shell current working directory (defaults to the parent process working directory).
The opts.env mapping passes additional environment variables to the shell.

Examples:

await sh("echo Hello World");
await sh(["echo Hello 1", "echo Hello 2", "echo Hello 3"]);
await sh("echo Hello World", { stdout: "null" });

shCapture

async function shCapture(command: string, opts: ShCaptureOpts = {}): Promise<ShOutput>;

Execute command in the command shell and return a promise for {code, output, error} (the exit code, the stdout output and the stderr output).

If the opts.input string has been assigned then it is piped to the shell stdin.
opts.cwd sets the shell current working directory (defaults to the parent process working directory).
The opts.env mapping passes additional environment variables to the shell.
opts.stdout and opts.stderr have Deno.RunOptions semantics. opts.stdout defaults to "piped". opts.stderr defaults to "inherit" (to capture stderr set opts.stderr to "piped").

Examples:

const { code, output } = await shCapture("echo Hello"); 
const { code, output, error } = await shCapture("mkdir tmpdir", { stderr: "piped" });

task

function task(name: string, prereqs?: string[], action?: Action): Task;

Create and register a task. Returns the task object.

name is a unique task name.
prereqs is an array of prerequisite task names. Prerequisites can be normal task names, file task names, file paths or globs (wildcards).
action is an optional function that is run if the task is selected for execution (type Action = (this: Task) => any;).
To fetch an existing task omit both the prereqs and action parameters.

writeFile

function writeFile(filename: string, text: string): boolean;

Write text to a file synchronously. If the file exists it will be overwritten. Returns true if a new file was created; returns false if the file already exists.

updateFile

function updateFile(filename: string, find: RegExp, replace: string): boolean;

Find and replace in text file synchronously. If the file contents is unchanged return false. If the contents has changed write it to the file and return true.

vers

function vers(): string;

Returns the Drake version number string.