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🌌 expanded-elm

A wrapper for the Elm language compiler that expands it with:

Usage

To run this tool, you only need to have Deno and Elm installed on your system.

deno run -A xelm.ts make [INPUT_FILES] [OPTIONS] --output=[OUTPUT_FILE].js

Build

⚠️ Warning: Binaries built with deno compile do not support the --optimize=2 and --optimize=3 flags.

You can also build a binary by using deno compile:

git clone https://github.com/kress95/expanded-elm.git
cd expanded-elm
deno compile --output xelm -A xelm.ts

CLI

./xelm make [INPUT_FILES] [OPTIONS] --output=[OUTPUT_FILE].js

Replace [INPUT_FILES], [OPTIONS], and [OUTPUT_FILE] with the appropriate values.

In addition, you can also run the other commands from Elm, such as repl, init, reactor, install, bump, diff, and publish, directly within xelm. These commands are simply forwarded, so there's no reason not to invoke them directly through elm.

Options

The options available for xelm make include:

  • --project=<project-root>: Path to the root directory of the project. Defaults to the current working directory.
  • --compiler=<elm-binary>: The path to the Elm binary, which is elm by default.
  • --elm-home=<elm-home>: Use a custom directory for ELM_HOME, which is ~/.elm by default.
  • --output=<module-name>.mjs: Build an ECMAScript module.

    Warning: If you intend to use certain libraries like elm/http, you will need to utilize polyfills like:

  • --typescript=<runtime>: Generate TypeScript bindings for the given runtime. For example, --typescript=node generates bindings for node. Defaults to deno and requires a .mjs output.
  • --debug: Turn on the time-travelling debugger.
  • --transform: Enable loading find-and-replace transformations from README.md files.
  • --optimize=: Tune the optimization level.
    • 0 Disable all optimizations, same as omitting the flag.
    • 1 Same as running elm make --optimize.
    • 2 Same as running elm-optimize-level-2.
    • 3 Same as running elm-optimize-level-2 --optimize-speed.
  • --minify: Minify the output with terser, loading configuration from terser.config.json if available.
  • --report=<report-type>: You can say --report=json to get error messages as JSON.
  • --docs=<json-file>: Generate a JSON file with the documentation.
  • --test: Enable test mode. Can be used with elm-test-rs with the --compiler flag.

Example

./xelm Main.elm -o output.js --optimize=2 --minify

This example runs elm on the Main.elm file, optimizes the output with level 2 optimization, and minifies the resulting JavaScript code.

API

If you prefer a programmatic approach, you can import this tool as a library and incorporate it into your tooling.

elm(inputs, output, options)

elm(inputs: string[], output: string, options?: Options): Promise<Deno.CommandStatus>

Compiles the input files and performs additional postprocessing.

Parameter Description
inputs The input files to read.
output The name of the resulting JavaScript file.
options (Optional) The compiler options.

Returns: The status returned from the compiler.

options

The options field provides various compiler options for the API.

Field Description
projectRoot Path to the root directory of the project.
elmPath The path to the Elm binary.
elmHome Custom directory for ELM_HOME, which is ~/.elm by default.
typescript Generate TypeScript bindings for the given runtime.
debug Turn on the time-traveling debugger.
transformations List of find-and-replace transformations to apply.
optimize Tune the optimization level.
minify Minify the output with terser.
report Change how error messages are reported.
docs Generate a JSON file with the documentation.
test Enable test mode. Can be used with elm-test-rs.
output Controls how the logs from the compiler should be handled.

transformations

The transformations field of the options object is an array of simple find-and-replace rules applied to the compiled code.

Field Description
find Code to find.
replace Code to replace.

xelm(inputs, output, options)

xelm(inputs: string[], output: string, options?: ExtraOptions): Promise<Deno.CommandStatus>

Retrieve transformations from the project and dependency README.md files before compiling.

Parameter Description
inputs The input files to read.
output The name of the resulting JavaScript file.
options (Optional) The compiler options, including ExtraOptions.

Returns: The status returned from the compiler.

options

Provide the same options as before, along with:

Field Description
refresh Force refreshing the transformation cache.

cli(args)

cli(args: string[] = Deno.args): Promise<Deno.CommandStatus>

Executes the command-line interface (CLI).

Parameter Description
args (Optional) An array of command-line arguments

Returns: The status returned from the compiler.

Transformations

Transformations are simple find-and-replace rules that are applied to the built code before doing any additional post-processing.

The loader scans the main README.md file of the project, as well as the dependencies of the project, searching for a link to #98f5c378-5809-4e35-904e-d1c5c3a8154e. Afterwards, it matches pairs of JavaScript code blocks until it comes across an h1, h2, or h3 heading. If a non-JavaScript code block or an odd number of code blocks is found, an error is raised.

Preprocessor

The preprocessor is a small DSL included to enable testing and optimization of code transforms. It provides a simple syntax with two condition constructs and two variables.

Variables

The preprocessor supports the following variables:

  • debug: Represents the debug flag.
  • test: Represents the test flag.

Coditions

The preprocessor offers two condition constructs:

@IF
// @IF debug
console.log("This code is included when the debug flag is set");
// @END
@UNLESS
// @UNLESS test
console.log("This code is included when the test flag is not set");
// @END

Composition

You can combine multiple condition constructs and variables to create composed conditional logic. Here's an example:

// @IF debug
//   @IF test
console.log("This code is included when both debug and test flags are set");
//   @END
// @END

In the above example, the inner @IF construct is only evaluated if the debug flag is set. If both the debug and test flags are set, the code within the inner construct will be included.

By leveraging the preprocessor, you can selectively include or exclude code based on the specified conditions, allowing for efficient testing and optimization of your transforms.

Please note that the preprocessor has a limited syntax and supports only the debug and test variables. It does not provide support for additional custom variables or complex conditional logic.

Examples

One example of a library that requires post-processing is kress95/elm-html-convert. This library provides a transform in its README.md file. The unit tests included in the repository also rely on applying this transform.

In the context of an application, my elm-ssr-demo application is using kress95/elm-html-convert and, consequently, requires applying transformations to work. Although in this particular application xelm.ts is used programmatically.

This feature can easily break Elm safety guarantees, so avoid using it unless you really need it.

Unlicense (Public Domain)

This is free and unencumbered software released into the public domain.

Anyone is free to copy, modify, publish, use, compile, sell, or distribute this software, either in source code form or as a compiled binary, for any purpose, commercial or non-commercial, and by any means.

In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and all copyright interest in the software to the public domain. We make this dedication for the benefit of the public at large and to the detriment of our heirs and successors. We intend this dedication to be an overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

For more information, please refer to <http://unlicense.org/>