##Native Dart Less compiler/transformer to build .css files from .less files
Less-transformer for pub-serve, pub-build and Less-compiler for pub-run
This is a translation from Less 2.4.0 Javascript (over nodejs) to Dart. Is a pure Dart implementation for the server/developer side.
As transformer could work with .html
files, by converting <less>
tags to <style>
tags.
The package is a Less compiler with wrappers for use in command line or as a dart transformer. Also, it could be used in other Dart programs.
If you get the full distribution (tar.gz file), the bin directory has the lessc.dart
file
for use with pub run:
CMD> pub run lessc [args] file.less file.css
A working example: CMD> pub run lessc test/less/charsets.less
Example with error output: CMD> pub run lessc --no-color test/less/errors/import-subfolder1.less
For help: CMD> pub run lessc --help
You would need import the package, create the Less class and call the transform future. There is an example:
import 'dart:io';
import 'package:less_dart/less.dart';
main() {
List<String> args = [];
Less less = new Less();
args.add('-no-color');
args.add('--strict-math=on');
args.add('--strict-units=on');
args.add('less/charsets.less');
less.transform(args).then((exitCode){
stderr.write(less.stderr.toString());
stdout.writeln('\nstdout:');
stdout.write(less.stdout.toString());
});
}
Simply add the following lines to your pubspec.yaml
to work with the default options:
dependencies:
less_dart: any
transformers:
- less_dart
After adding the transformer all your .less
files will be automatically
transformed to corresponding .css
files. Also the .html
files will be processed.
This is the standard default, but it could be modified by inclusion or exclusion paths.
The exclusion paths start with '!'. And the '*' is supported in the paths.
The power of Dart builder is chain transformers, so a .less
file will be converted
to a .css
file and this could be the source for a polymer transformer, by example.
Consider to use the less transformer as the first in the chain.
You can also pass options to less_dart if necessary:
transformers:
- less_dart:
entry_points:
- path/to/builder.less
- or/other.less
output: /path/to/builded.css
include_path: /path/to/directory/for/less/includes
compress: true or false
build_mode: less, dart or mixed. (dart by default)
other_flags:
- to include in the lessc command line
silence: true
-
entry_points (or entry_point equivalent):
- If not supplied process all '.less' and '.html' files.
- Could be a list of files to process, as example: ['web/file1.less', 'web/file2.less'].
- Could be, also, a pattern for inclusion, as example: ['*.less'].
- Or have exclusion patterns that start with '!', as example: ['.less', '!/lib/.less'].
-
output - Is the '.css' file generated. Only works when one (only one) '.less' file is add to entry_points. No '*' must be found in the path. Is independent from '.html' files. If not supplied, or several '.less' are processed, then input file '.less' with extension changed to '.css' is used.
-
include_path - see Less Documentation include_path.
-
compress - see Less Documentation compress.
-
build_mode -
- less - command
CMD> lessc --flags input.less output.css
is used. (output.css is in the same directory as input.less) - dart - command
CMD> lessc --flags -
with stdin and stdout piped in the dart transformer process. See build folder for the css file. - mixed - command
CMD> lessc --flags input.less
with stdout managed by the dart transformer process. See build folder for the css file.
- less - command
-
other_flags - Let add other flags such as (--source-map, ...) in the lessc command line.
-
silence - Only log error messages to transformer window.
When a .html
file is processed, the transformer look for <less>...</less>
tags and then the equivalent <style>...</style>
tags are added below, and at the same level.
All the <less>
attributes are copied, except 'replace'. With this attribute <less>
tags are removed in the final file.
The <less>
tags in the final file are stamped with style="display:none"
attribute, to avoid conflicts, easing debugging.
A .html
could have various <less>...</less>
pairs.
Example for a polymer component:
<polymer-element name="test">
<template>
<less>
@color: red;
:host {
background-color: @color;
}
</less>
<div>
...
Will result in:
<polymer-element name="test">
<template>
<less style="display:none">
@color: red;
:host {
background-color: @color;
}
</less>
<style>
:host {
background-color: red;
}
</style>
<div>
...
- Javascript evaluation is not supported.
- If this is a problem use less_node.
- Alternatively you can use 'Custom Functions' (see test/custom_functions_test.dart') from your dart program.
- Added option
--banner=bannerfile.txt
. - Added directive
@options "--flags";
. Intended to be the first line in a less file/tag, acts globally. This directive let specify individual options in batch processing. Example:@options "--strict-math=on --strict-units=on --include-path=test/data";
. - Modified directive
@plugin "lib";
. lib is the plugin name and must exist as dart code in the plugins directory. By now only@plugin "less-plugin-advanced-color-functions";
is operative.
-
The transformer has been rebuild recently. If the new behavior is not right, you could use the previous version:
transformers: - less_dart/deprecated/transformer: entry_point: ...
-
Pass the standard tests in windows (no tested in linux).
-
cleanCSS (as plugin) not implemented yet.
-
Error color output. Implemented, but not tested in linux. In windows cmd don't support the color commands.
Copyright (c) 2009-2015 Alexis Sellier & The Core Less Team.
Copyright (c) 2014-2015 Adalberto Lacruz for dart translation.
Licensed under the Apache License.