mirror of
https://github.com/cheat/cheat.git
synced 2024-11-23 22:41:35 +01:00
323 lines
17 KiB
Markdown
323 lines
17 KiB
Markdown
# Chroma — A general purpose syntax highlighter in pure Go
|
|
|
|
[](https://godoc.org/github.com/alecthomas/chroma) [](https://github.com/alecthomas/chroma/actions/workflows/ci.yml) [](https://invite.slack.golangbridge.org/)
|
|
|
|
Chroma takes source code and other structured text and converts it into syntax
|
|
highlighted HTML, ANSI-coloured text, etc.
|
|
|
|
Chroma is based heavily on [Pygments](http://pygments.org/), and includes
|
|
translators for Pygments lexers and styles.
|
|
|
|
<a id="markdown-table-of-contents" name="table-of-contents"></a>
|
|
|
|
## Table of Contents
|
|
|
|
<!-- TOC -->
|
|
|
|
1. [Table of Contents](#table-of-contents)
|
|
2. [Supported languages](#supported-languages)
|
|
3. [Try it](#try-it)
|
|
4. [Using the library](#using-the-library)
|
|
1. [Quick start](#quick-start)
|
|
2. [Identifying the language](#identifying-the-language)
|
|
3. [Formatting the output](#formatting-the-output)
|
|
4. [The HTML formatter](#the-html-formatter)
|
|
5. [More detail](#more-detail)
|
|
1. [Lexers](#lexers)
|
|
2. [Formatters](#formatters)
|
|
3. [Styles](#styles)
|
|
6. [Command-line interface](#command-line-interface)
|
|
7. [Testing lexers](#testing-lexers)
|
|
8. [What's missing compared to Pygments?](#whats-missing-compared-to-pygments)
|
|
|
|
<!-- /TOC -->
|
|
|
|
<a id="markdown-supported-languages" name="supported-languages"></a>
|
|
|
|
## Supported languages
|
|
|
|
| Prefix | Language |
|
|
| :----: | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
|
|
| A | ABAP, ABNF, ActionScript, ActionScript 3, Ada, Agda, AL, Alloy, Angular2, ANTLR, ApacheConf, APL, AppleScript, ArangoDB AQL, Arduino, ArmAsm, AutoHotkey, AutoIt, Awk |
|
|
| B | Ballerina, Bash, Bash Session, Batchfile, BibTeX, Bicep, BlitzBasic, BNF, BQN, Brainfuck |
|
|
| C | C, C#, C++, Caddyfile, Caddyfile Directives, Cap'n Proto, Cassandra CQL, Ceylon, CFEngine3, cfstatement, ChaiScript, Chapel, Cheetah, Clojure, CMake, COBOL, CoffeeScript, Common Lisp, Coq, Crystal, CSS, Cython |
|
|
| D | D, Dart, Dax, Diff, Django/Jinja, dns, Docker, DTD, Dylan |
|
|
| E | EBNF, Elixir, Elm, EmacsLisp, Erlang |
|
|
| F | Factor, Fennel, Fish, Forth, Fortran, FortranFixed, FSharp |
|
|
| G | GAS, GDScript, Genshi, Genshi HTML, Genshi Text, Gherkin, GLSL, Gnuplot, Go, Go HTML Template, Go Text Template, GraphQL, Groff, Groovy |
|
|
| H | Handlebars, Hare, Haskell, Haxe, HCL, Hexdump, HLB, HLSL, HolyC, HTML, HTTP, Hy |
|
|
| I | Idris, Igor, INI, Io, ISCdhcpd |
|
|
| J | J, Java, JavaScript, JSON, Julia, Jungle |
|
|
| K | Kotlin |
|
|
| L | Lighttpd configuration file, LLVM, Lua |
|
|
| M | Makefile, Mako, markdown, Mason, Mathematica, Matlab, mcfunction, Meson, Metal, MiniZinc, MLIR, Modula-2, MonkeyC, MorrowindScript, Myghty, MySQL |
|
|
| N | NASM, Natural, Newspeak, Nginx configuration file, Nim, Nix |
|
|
| O | Objective-C, OCaml, Octave, Odin, OnesEnterprise, OpenEdge ABL, OpenSCAD, Org Mode |
|
|
| P | PacmanConf, Perl, PHP, PHTML, Pig, PkgConfig, PL/pgSQL, plaintext, Plutus Core, Pony, PostgreSQL SQL dialect, PostScript, POVRay, PowerQuery, PowerShell, Prolog, PromQL, properties, Protocol Buffer, PRQL, PSL, Puppet, Python, Python 2 |
|
|
| Q | QBasic, QML |
|
|
| R | R, Racket, Ragel, Raku, react, ReasonML, reg, reStructuredText, Rexx, Ruby, Rust |
|
|
| S | SAS, Sass, Scala, Scheme, Scilab, SCSS, Sed, Sieve, Smali, Smalltalk, Smarty, Snobol, Solidity, SourcePawn, SPARQL, SQL, SquidConf, Standard ML, stas, Stylus, Svelte, Swift, SYSTEMD, systemverilog |
|
|
| T | TableGen, Tal, TASM, Tcl, Tcsh, Termcap, Terminfo, Terraform, TeX, Thrift, TOML, TradingView, Transact-SQL, Turing, Turtle, Twig, TypeScript, TypoScript, TypoScriptCssData, TypoScriptHtmlData |
|
|
| V | V, V shell, Vala, VB.net, verilog, VHDL, VHS, VimL, vue |
|
|
| W | WDTE, WebGPU Shading Language, Whiley |
|
|
| X | XML, Xorg |
|
|
| Y | YAML, YANG |
|
|
| Z | Z80 Assembly, Zed, Zig |
|
|
|
|
_I will attempt to keep this section up to date, but an authoritative list can be
|
|
displayed with `chroma --list`._
|
|
|
|
<a id="markdown-try-it" name="try-it"></a>
|
|
|
|
## Try it
|
|
|
|
Try out various languages and styles on the [Chroma Playground](https://swapoff.org/chroma/playground/).
|
|
|
|
<a id="markdown-using-the-library" name="using-the-library"></a>
|
|
|
|
## Using the library
|
|
|
|
Chroma, like Pygments, has the concepts of
|
|
[lexers](https://github.com/alecthomas/chroma/tree/master/lexers),
|
|
[formatters](https://github.com/alecthomas/chroma/tree/master/formatters) and
|
|
[styles](https://github.com/alecthomas/chroma/tree/master/styles).
|
|
|
|
Lexers convert source text into a stream of tokens, styles specify how token
|
|
types are mapped to colours, and formatters convert tokens and styles into
|
|
formatted output.
|
|
|
|
A package exists for each of these, containing a global `Registry` variable
|
|
with all of the registered implementations. There are also helper functions
|
|
for using the registry in each package, such as looking up lexers by name or
|
|
matching filenames, etc.
|
|
|
|
In all cases, if a lexer, formatter or style can not be determined, `nil` will
|
|
be returned. In this situation you may want to default to the `Fallback`
|
|
value in each respective package, which provides sane defaults.
|
|
|
|
<a id="markdown-quick-start" name="quick-start"></a>
|
|
|
|
### Quick start
|
|
|
|
A convenience function exists that can be used to simply format some source
|
|
text, without any effort:
|
|
|
|
```go
|
|
err := quick.Highlight(os.Stdout, someSourceCode, "go", "html", "monokai")
|
|
```
|
|
|
|
<a id="markdown-identifying-the-language" name="identifying-the-language"></a>
|
|
|
|
### Identifying the language
|
|
|
|
To highlight code, you'll first have to identify what language the code is
|
|
written in. There are three primary ways to do that:
|
|
|
|
1. Detect the language from its filename.
|
|
|
|
```go
|
|
lexer := lexers.Match("foo.go")
|
|
```
|
|
|
|
2. Explicitly specify the language by its Chroma syntax ID (a full list is available from `lexers.Names()`).
|
|
|
|
```go
|
|
lexer := lexers.Get("go")
|
|
```
|
|
|
|
3. Detect the language from its content.
|
|
|
|
```go
|
|
lexer := lexers.Analyse("package main\n\nfunc main()\n{\n}\n")
|
|
```
|
|
|
|
In all cases, `nil` will be returned if the language can not be identified.
|
|
|
|
```go
|
|
if lexer == nil {
|
|
lexer = lexers.Fallback
|
|
}
|
|
```
|
|
|
|
At this point, it should be noted that some lexers can be extremely chatty. To
|
|
mitigate this, you can use the coalescing lexer to coalesce runs of identical
|
|
token types into a single token:
|
|
|
|
```go
|
|
lexer = chroma.Coalesce(lexer)
|
|
```
|
|
|
|
<a id="markdown-formatting-the-output" name="formatting-the-output"></a>
|
|
|
|
### Formatting the output
|
|
|
|
Once a language is identified you will need to pick a formatter and a style (theme).
|
|
|
|
```go
|
|
style := styles.Get("swapoff")
|
|
if style == nil {
|
|
style = styles.Fallback
|
|
}
|
|
formatter := formatters.Get("html")
|
|
if formatter == nil {
|
|
formatter = formatters.Fallback
|
|
}
|
|
```
|
|
|
|
Then obtain an iterator over the tokens:
|
|
|
|
```go
|
|
contents, err := ioutil.ReadAll(r)
|
|
iterator, err := lexer.Tokenise(nil, string(contents))
|
|
```
|
|
|
|
And finally, format the tokens from the iterator:
|
|
|
|
```go
|
|
err := formatter.Format(w, style, iterator)
|
|
```
|
|
|
|
<a id="markdown-the-html-formatter" name="the-html-formatter"></a>
|
|
|
|
### The HTML formatter
|
|
|
|
By default the `html` registered formatter generates standalone HTML with
|
|
embedded CSS. More flexibility is available through the `formatters/html` package.
|
|
|
|
Firstly, the output generated by the formatter can be customised with the
|
|
following constructor options:
|
|
|
|
- `Standalone()` - generate standalone HTML with embedded CSS.
|
|
- `WithClasses()` - use classes rather than inlined style attributes.
|
|
- `ClassPrefix(prefix)` - prefix each generated CSS class.
|
|
- `TabWidth(width)` - Set the rendered tab width, in characters.
|
|
- `WithLineNumbers()` - Render line numbers (style with `LineNumbers`).
|
|
- `WithLinkableLineNumbers()` - Make the line numbers linkable and be a link to themselves.
|
|
- `HighlightLines(ranges)` - Highlight lines in these ranges (style with `LineHighlight`).
|
|
- `LineNumbersInTable()` - Use a table for formatting line numbers and code, rather than spans.
|
|
|
|
If `WithClasses()` is used, the corresponding CSS can be obtained from the formatter with:
|
|
|
|
```go
|
|
formatter := html.New(html.WithClasses(true))
|
|
err := formatter.WriteCSS(w, style)
|
|
```
|
|
|
|
<a id="markdown-more-detail" name="more-detail"></a>
|
|
|
|
## More detail
|
|
|
|
<a id="markdown-lexers" name="lexers"></a>
|
|
|
|
### Lexers
|
|
|
|
See the [Pygments documentation](http://pygments.org/docs/lexerdevelopment/)
|
|
for details on implementing lexers. Most concepts apply directly to Chroma,
|
|
but see existing lexer implementations for real examples.
|
|
|
|
In many cases lexers can be automatically converted directly from Pygments by
|
|
using the included Python 3 script `pygments2chroma_xml.py`. I use something like
|
|
the following:
|
|
|
|
```sh
|
|
python3 _tools/pygments2chroma_xml.py \
|
|
pygments.lexers.jvm.KotlinLexer \
|
|
> lexers/embedded/kotlin.xml
|
|
```
|
|
|
|
See notes in [pygments-lexers.txt](https://github.com/alecthomas/chroma/blob/master/pygments-lexers.txt)
|
|
for a list of lexers, and notes on some of the issues importing them.
|
|
|
|
<a id="markdown-formatters" name="formatters"></a>
|
|
|
|
### Formatters
|
|
|
|
Chroma supports HTML output, as well as terminal output in 8 colour, 256 colour, and true-colour.
|
|
|
|
A `noop` formatter is included that outputs the token text only, and a `tokens`
|
|
formatter outputs raw tokens. The latter is useful for debugging lexers.
|
|
|
|
<a id="markdown-styles" name="styles"></a>
|
|
|
|
### Styles
|
|
|
|
Chroma styles are defined in XML. The style entries use the
|
|
[same syntax](http://pygments.org/docs/styles/) as Pygments.
|
|
|
|
All Pygments styles have been converted to Chroma using the `_tools/style.py`
|
|
script.
|
|
|
|
When you work with one of [Chroma's styles](https://github.com/alecthomas/chroma/tree/master/styles),
|
|
know that the `Background` token type provides the default style for tokens. It does so
|
|
by defining a foreground color and background color.
|
|
|
|
For example, this gives each token name not defined in the style a default color
|
|
of `#f8f8f8` and uses `#000000` for the highlighted code block's background:
|
|
|
|
```xml
|
|
<entry type="Background" style="#f8f8f2 bg:#000000"/>
|
|
```
|
|
|
|
Also, token types in a style file are hierarchical. For instance, when `CommentSpecial` is not defined, Chroma uses the token style from `Comment`. So when several comment tokens use the same color, you'll only need to define `Comment` and override the one that has a different color.
|
|
|
|
For a quick overview of the available styles and how they look, check out the [Chroma Style Gallery](https://xyproto.github.io/splash/docs/).
|
|
|
|
<a id="markdown-command-line-interface" name="command-line-interface"></a>
|
|
|
|
## Command-line interface
|
|
|
|
A command-line interface to Chroma is included.
|
|
|
|
Binaries are available to install from [the releases page](https://github.com/alecthomas/chroma/releases).
|
|
|
|
The CLI can be used as a preprocessor to colorise output of `less(1)`,
|
|
see documentation for the `LESSOPEN` environment variable.
|
|
|
|
The `--fail` flag can be used to suppress output and return with exit status
|
|
1 to facilitate falling back to some other preprocessor in case chroma
|
|
does not resolve a specific lexer to use for the given file. For example:
|
|
|
|
```shell
|
|
export LESSOPEN='| p() { chroma --fail "$1" || cat "$1"; }; p "%s"'
|
|
```
|
|
|
|
Replace `cat` with your favourite fallback preprocessor.
|
|
|
|
When invoked as `.lessfilter`, the `--fail` flag is automatically turned
|
|
on under the hood for easy integration with [lesspipe shipping with
|
|
Debian and derivatives](https://manpages.debian.org/lesspipe#USER_DEFINED_FILTERS);
|
|
for that setup the `chroma` executable can be just symlinked to `~/.lessfilter`.
|
|
|
|
<a id="markdown-whats-missing-compared-to-pygments" name="whats-missing-compared-to-pygments"></a>
|
|
|
|
<a id="markdown-testing-lexers" name="testing-lexers"></a>
|
|
|
|
## Testing lexers
|
|
|
|
If you edit some lexers and want to try it, open a shell in `cmd/chromad` and run:
|
|
|
|
```shell
|
|
go run .
|
|
```
|
|
|
|
A Link will be printed. Open it in your Browser. Now you can test on the Playground with your local changes.
|
|
|
|
If you want to run the tests and the lexers, open a shell in the root directory and run:
|
|
|
|
```shell
|
|
go test ./lexers
|
|
```
|
|
|
|
When updating or adding a lexer, please add tests. See [lexers/README.md](lexers/README.md) for more.
|
|
|
|
## What's missing compared to Pygments?
|
|
|
|
- Quite a few lexers, for various reasons (pull-requests welcome):
|
|
- Pygments lexers for complex languages often include custom code to
|
|
handle certain aspects, such as Raku's ability to nest code inside
|
|
regular expressions. These require time and effort to convert.
|
|
- I mostly only converted languages I had heard of, to reduce the porting cost.
|
|
- Some more esoteric features of Pygments are omitted for simplicity.
|
|
- Though the Chroma API supports content detection, very few languages support them.
|
|
I have plans to implement a statistical analyser at some point, but not enough time.
|