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Reference: languages coloured

Neutral description of which files Turbo Golo colours, how it decides, and what each scanner recognises.

Recognition

A file's extension decides whenever it is one of these:

Extension Language
.golo Golo
.toml TOML
.yaml, .yml YAML
.md, .markdown Markdown
.js, .mjs, .cjs JavaScript
.html, .htm HTML
.xml, .xsd, .xsl, .xslt, .svg, .plist, .csproj, .pom XML
.sh, .bash, .zsh Shell
.dockerfile, .containerfile Dockerfile

Extensions are matched case-insensitively, and only the last one counts: notes.golo.md is Markdown, and main.golo.backup is not Golo.

A file whose extension decides nothing is looked up by name next. Only files that carry no useful extension need this:

Name Language
Dockerfile, Containerfile Dockerfile

A name matches on the whole of it or on the part before the first dot, ignoring case — so Dockerfile, dockerfile and Dockerfile.dev are all recognised, while Dockerfile.md is Markdown, because the extension is consulted first.

A file that neither table claims is read by its first line. A shebang naming golo makes it Golo: # opens a comment in Golo, so the interpreter reads the line as one, and a script installed without its extension and run as a command is Golo and nothing else. A shebang naming a shell — sh, bash, zsh, dash or ksh — makes it a shell script. The interpreter is recognised as a path element or as the argument to env.

First line Result
#!/usr/bin/env golo Golo
#!/usr/local/bin/golo Golo
#!/bin/sh Shell
#!/usr/bin/env bash Shell
#!/usr/bin/env -S bash -e Shell
#!/usr/bin/env node Not coloured
Anything not starting #! Not coloured

The order is fixed — extension, then name, then first line — and the first to decide wins.

Everything else is shown in plain text. That is not an error — opening a PNG in the editor is not a mistake, it is just not coloured.

Classes

Every scanner produces the same vocabulary of classes, and each maps to one theme key.

Class Theme key Produced by
identifier syntax.identifier Golo, TOML, JavaScript, shell, YAML, Dockerfile
keyword syntax.keyword Golo, JavaScript, shell, HTML (doctype), XML, Dockerfile
type syntax.type Golo (capitalised names and module paths), TOML (table headers), YAML (tags)
builtin syntax.builtin Golo (the interpreter's functions), JavaScript, shell (builtins and expansions), YAML (anchors and aliases), Dockerfile (variables)
constant syntax.constant Golo, TOML, JavaScript, shell, YAML, HTML and XML (entities)
function syntax.function Golo, JavaScript, shell (the command)
string syntax.string all
char syntax.char Golo ('c')
number syntax.number Golo, TOML, JavaScript, shell, YAML, Dockerfile
comment syntax.comment Golo, TOML, JavaScript, shell, HTML, YAML, XML, Dockerfile
operator syntax.operator Golo, TOML, JavaScript, shell, HTML, YAML (block scalar headers), XML, Dockerfile
punctuation syntax.punctuation Golo, TOML, JavaScript, shell, Markdown, YAML, Dockerfile
heading syntax.heading Markdown
tag syntax.tag HTML, XML
attribute syntax.attribute HTML, XML, Dockerfile (flags)
emphasis syntax.emphasis Markdown
link syntax.link Markdown

Golo produces no heading, tag, attribute, emphasis or link span. In turbo-classic, syntax.number and syntax.constant are both magenta and syntax.char is the green of syntax.string, so 42 and true share a colour there and so do 'x' and "x"; other themes separate them. See how to write your own theme if you want to change it.

Golo

Hand-written, in internal/gololang, against GoloScript's lexer/lexer.go and token/token.go. What the lexer reads as one token, the scanner colours as one span.

Four constructs cross a line break, and are carried to the next line exactly as the lexer reads them: a ---- block comment to its closing ----; a "…" string to its closing quote; a """…""" multi-line string to its closing three quotes; a '…' character literal to its closing apostrophe. None of the four nests. So an unterminated string colours the rest of the file, until a quote — which is what the interpreter reads it as.

Recognised As
and, augment, augmentation, await, break, case, catch, continue, else, finally, for, foreach, function, if, import, in, is, isnt, let, local, match, module, not, oftype, or, orIfNull, otherwise, return, spawn, struct, then, throw, try, union, var, when, while, with keyword
true, false, null constant
the interpreter's 157 builtins — println, print, str, len, list, map, set, array, vector, range, readFile, toJSON, fromJSON, httpGet, DynamicObject, … builtin
any other name starting with an ASCII capital — Point, Shape, Circle, Result_Failure, Some type
the dotted path after module or importhello.World, gololang.Errors, java.util.List — as one span type
the name after functionmain in function main = |args| function
any other lower-case name immediately before ( function
any other name: any Unicode letter or mark, _, or an emoji, then letters, digits and the same — x, été, 名前, 😀, 🚀launch identifier
"…" with \n \t \r \\ \" \' \0 \xHH escapes, across lines string
"""…""", across lines, no escapes string
'…' with the same escapes, across lines char
42, 3.14, 1.5e-3, 2E10, 42L, 3.14F, 2.0f number
# to the end of the line, a shebang included comment
--------, across lines comment
.., ... operator
runs of +-*/%=<>!&|^~?: — including ->, ?:, ==, !=, <=, >= operator
()[]{},; and a lone . punctuation
$ in augment Shape$Circle punctuation

A point joins a number only when a digit follows it. That is the lexer's own test, and it is what keeps 1..3 a number and a range rather than the double 1. and a stray .3.

An exponent may have no digits. The lexer reads 1e as a float and leaves the parser to complain, so 1e is one number span.

A capitalised name is a type by convention, not by rule. Golo lets you write let Count = 1, and it is coloured as a type all the same. Structs, unions, variants and augmentation targets are what people capitalise, and the colour follows the people.

Some, None, Ok and Err are types, not constants. They are variants of ordinary unions declared in gololang.Errors, available after an import, not builtins.

DynamicObject is a builtin, capital and all. It is in the interpreter's table, and the table wins over the case rule.

Names may hold any Unicode letter, and emoji. The lexer's isLetter admits letters, marks, _ and four emoji blocks (emoticons, miscellaneous symbols and pictographs, transport and map symbols, supplemental symbols and pictographs); the scanner uses the same rule.

Colouring follows the lexer, not the parser. GoloScript's parser, as of v0.1.1, refuses several tokens its lexer reads: the L, F and f suffixes, a 'c' character literal, the .. range, orIfNull, oftype and local function. They are coloured as the lexer reads them, and the language server marks the line when the parser refuses it. demos/syntax-tour/lexer-only.golo holds one of each.

Not recognised, each for a stated reason:

Not recognised Because
1_000 as one number The lexer has no digit separator: _ starts a name, so this is 1 and then _000
0xFF, 0b1010, 0o17 as numbers The lexer has no base prefixes: 0xFF is 0 and then the name xFF
.5 as a number The lexer requires a digit before the point, so this is a dot and then 5
42l as a long The lexer accepts only the upper-case L, so this is 42 and the name l
--- as a comment Four dashes open a block comment; three are an operator run
A keyword after : as a method name obj: match() keeps match a keyword — the scanner does not track what a colon introduces
An escape inside """…""" The lexer appends every rune until the three quotes, so """a\""" ends at its first """
A constructor as anything but a type Nothing in the syntax separates Circle(1.0) from a type applied to arguments
An unterminated string stopping at its line The interpreter reads to the closing quote wherever it is, so the colour follows it — the opposite of Turbo MoonBit's decision, for the opposite reason
Whether a name is bound in this scope Nothing here reads more than one line at a time; that is the language server's question, and F1 answers it

TOML

Recognised As
# comment comment
[table], [[array]] the name as a type, the brackets as punctuation
key = identifier, then operator
"basic", 'literal', """multi-line""", '''multi-line''' string
true, false constant
numbers, dates, times, inf, nan number

YAML

A compose file, a Kubernetes manifest and a CI workflow are all this: there is no separate dialect, because a dialect would be somebody else's schema to keep in step with.

Recognised As
# comment comment
key: before a space or the end of the line the key as an identifier, the colon as punctuation
"quoted": 1, 'quoted': 1 the quoted key as an identifier
- opening a sequence entry punctuation
"…", '…' string
true, false, yes, no, on, off, null constant, whatever their case
numbers, dates and times written without quotes number
&anchor, *alias builtin
!!str, !Custom type
---, ... the whole line as punctuation
{, }, [, ], , punctuation
|, >, with their chomping and indentation indicators the header as an operator, the body as a string

A colon is a separator only when a space or the end of the line follows it. image: nginx:1.27 is a key and one value, and url: http://example.com/x is a key and one URL — colouring the inner colons as separators would put every image tag and every URL in three colours.

A block scalar's extent is decided by indentation, not by a delimiter. The first content line after | or > fixes the block's indentation; every line indented at least that far belongs to it, and the first line that is not ends it. A blank line inside a block stays inside it: a literal scalar keeps its empty lines, and ending the block at the first paragraph break would cut a shell script in a CI file in half.

A # needs a space before it to start a comment, so colour: ff#00aa is one scalar.

Not recognised Because
The schema of a compose file, a manifest or a workflow Colouring services: differently from any other key means carrying somebody else's schema, and it goes stale the day they add a key
Multi-document streams as separate documents --- is coloured, but nothing is reset at it; nothing in the colouring depends on document boundaries
Whether a bare word is a string or a number to a parser 1.2.3 is a version to a reader and a string to YAML; the scanner colours what it looks like

Markdown

Recognised As
# Heading###### Heading the whole line as a heading
**bold**, __bold__, *italic*, _italic_ emphasis
`code` string
[text](target), ![alt](src) the whole thing as a link
- , * , + , 1. , 1) the marker as punctuation
> punctuation
---, ***, ___ punctuation
``` and ~~~ fences the whole block, opening and closing lines included, as a string

A fenced block is one colour whatever language it announces: ```golo does not colour its contents as Golo. The run of markers that opens a block must be matched by the same character to close it, so a backtick fence is not closed by a tilde one. An unclosed fence colours to the end of the file.

The run of markers opening emphasis must be matched by a run of the same length, so **bold** is one span rather than two italics.

JavaScript

Recognised As
const, let, function, class, async, await, import, export, … keyword
true, false, null, undefined, NaN, Infinity, this constant
console, document, window, Array, Object, Promise, Math, JSON, … builtin
a name immediately before ( function
"…", '…' string
`…`, interpolations included, across lines string
// to end of line, /* … */ across lines comment
42, 3.14, 0x1f, 0b1010, 0o777, 1_000_000, 1e6, 10n number
runs of `+-*/%=<>!& ^~?:`
()[]{},;. punctuation

Regular-expression literals are not recognised. Telling /x/g from a division needs to know whether the previous token could end an expression; a wrong guess colours the rest of a line as a string, which is worse than leaving a regex the colour of an operator.

Globals are recognised by name, so a file that shadows Math still has it coloured as a builtin — the same rule Golo's builtins follow here.

HTML

Recognised As
<tag, </tag, >, /> tag
attribute names, including data-*, xlink:href, @click, v-bind.prop attribute
= operator
"…", '…' string
<!-- … -->, across lines comment
&amp;, &#169; constant
<!DOCTYPE …> and other declarations keyword

Text between tags is not coloured. A bare & with no ; within 32 characters is left alone, because it is legal text.

The contents of <script> and <style> are not coloured as JavaScript and CSS.

XML

Its own scanner rather than HTML's, for one reason that matters: CDATA. The whole point of <![CDATA[ … ]]> is that its contents are not markup, and colouring the tags inside one as tags is exactly backwards.

Recognised As
<?xml version="1.0"?> and other processing instructions the target and ?> as keyword, the pairs between as attributes and strings
<!DOCTYPE …> and the other <! forms keyword
<!-- … -->, across lines comment
<![CDATA[ … ]]>, across lines string
<tag, </tag, >, /> tag
<ns:tag>, xsi:type the prefix and the local name as one span
attribute names attribute
= operator
"…", '…' string
&amp;, &#169; constant

A comment and a CDATA section close on different delimiters, and are carried separately: a --> inside a CDATA section does not end it.

A bare & with no semicolon within 32 characters is left alone, because it is legal text in plenty of documents and swallowing the rest of the line would be the bigger mistake.

Text between tags is not coloured.

Shell

Applies to sh, bash and zsh alike: the keywords recognised are the ones they share.

Recognised As
if, then, fi, for, while, case, esac, function, return, … keyword
true, false constant
echo, printf, export, local, read, cd, set, source, … builtin
$NAME, ${…}, $(…), $1, $?, $@ builtin
the first bare word on a line function
every later bare word, and NAME in NAME=value identifier
'…', with nothing escaped or expanded inside string
"…", with the expansions inside it coloured as expansions string
# to end of line comment

$(a $(b) c) is one span: nesting is counted. An option such as -euo is one word, not a minus and a word.

Heredocs are not recognised. <<EOF and the text after it are coloured as ordinary shell.

Dockerfile

Recognised As
FROM, RUN, COPY, ADD, ARG, ENV, CMD, ENTRYPOINT, EXPOSE, LABEL, USER, VOLUME, WORKDIR, HEALTHCHECK, ONBUILD, SHELL, STOPSIGNAL, MAINTAINER keyword, in any case
AS, NONE keyword
# comment, including the # syntax= and # escape= directives comment
--from=builder, --chown=me:me the flag name as an attribute
$NAME, ${NAME}, ${NAME:-default} builtin, as one span to the closing brace
"…", '…' string
a trailing \ operator
numbers number
paths and image references — /usr/local/bin, golang:1.26-alpine identifier, as one span

Only the first word of a line can be an instruction, and a word that is not one is an argument — which is what keeps a continuation line's first word out of the keyword colour.

Nothing crosses a line break. A \ joins two lines for Docker, but each half still reads as a command and is coloured on its own.

Not recognised Because
The shell inside a RUN It would mean running the shell scanner over part of a line and mapping its columns out, and RUN may hold any language
Heredocs in a RUN The same reason the shell scanner does not recognise them
Which stage a --from names Nothing here reads the rest of the file

See also

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# Reference: languages coloured

> Neutral description of which files Turbo Golo colours, how it decides, and what each scanner recognises.

## Recognition

A file's **extension** decides whenever it is one of these:

| Extension | Language |
| --- | --- |
| `.golo` | Golo |
| `.toml` | TOML |
| `.yaml`, `.yml` | YAML |
| `.md`, `.markdown` | Markdown |
| `.js`, `.mjs`, `.cjs` | JavaScript |
| `.html`, `.htm` | HTML |
| `.xml`, `.xsd`, `.xsl`, `.xslt`, `.svg`, `.plist`, `.csproj`, `.pom` | XML |
| `.sh`, `.bash`, `.zsh` | Shell |
| `.dockerfile`, `.containerfile` | Dockerfile |

Extensions are matched case-insensitively, and only the last one counts: `notes.golo.md` is Markdown, and `main.golo.backup` is not Golo.

A file whose extension decides nothing is looked up by **name** next. Only files that carry no useful extension need this:

| Name | Language |
| --- | --- |
| `Dockerfile`, `Containerfile` | Dockerfile |

A name matches on the whole of it or on the part before the first dot, ignoring case — so `Dockerfile`, `dockerfile` and `Dockerfile.dev` are all recognised, while `Dockerfile.md` is Markdown, because the extension is consulted first.

A file that neither table claims is read by its **first line**. A shebang naming `golo` makes it Golo: `#` opens a comment in Golo, so the interpreter reads the line as one, and a script installed without its extension and run as a command is Golo and nothing else. A shebang naming a shell — `sh`, `bash`, `zsh`, `dash` or `ksh` — makes it a shell script. The interpreter is recognised as a path element or as the argument to `env`.

| First line | Result |
| --- | --- |
| `#!/usr/bin/env golo` | Golo |
| `#!/usr/local/bin/golo` | Golo |
| `#!/bin/sh` | Shell |
| `#!/usr/bin/env bash` | Shell |
| `#!/usr/bin/env -S bash -e` | Shell |
| `#!/usr/bin/env node` | Not coloured |
| Anything not starting `#!` | Not coloured |

The order is fixed — extension, then name, then first line — and the first to decide wins.

Everything else is shown in plain text. That is not an error — opening a PNG in the editor is not a mistake, it is just not coloured.

## Classes

Every scanner produces the same vocabulary of classes, and each maps to one theme key.

| Class | Theme key | Produced by |
| --- | --- | --- |
| `identifier` | `syntax.identifier` | Golo, TOML, JavaScript, shell, YAML, Dockerfile |
| `keyword` | `syntax.keyword` | Golo, JavaScript, shell, HTML (doctype), XML, Dockerfile |
| `type` | `syntax.type` | Golo (capitalised names and module paths), TOML (table headers), YAML (tags) |
| `builtin` | `syntax.builtin` | Golo (the interpreter's functions), JavaScript, shell (builtins and expansions), YAML (anchors and aliases), Dockerfile (variables) |
| `constant` | `syntax.constant` | Golo, TOML, JavaScript, shell, YAML, HTML and XML (entities) |
| `function` | `syntax.function` | Golo, JavaScript, shell (the command) |
| `string` | `syntax.string` | all |
| `char` | `syntax.char` | Golo (`'c'`) |
| `number` | `syntax.number` | Golo, TOML, JavaScript, shell, YAML, Dockerfile |
| `comment` | `syntax.comment` | Golo, TOML, JavaScript, shell, HTML, YAML, XML, Dockerfile |
| `operator` | `syntax.operator` | Golo, TOML, JavaScript, shell, HTML, YAML (block scalar headers), XML, Dockerfile |
| `punctuation` | `syntax.punctuation` | Golo, TOML, JavaScript, shell, Markdown, YAML, Dockerfile |
| `heading` | `syntax.heading` | Markdown |
| `tag` | `syntax.tag` | HTML, XML |
| `attribute` | `syntax.attribute` | HTML, XML, Dockerfile (flags) |
| `emphasis` | `syntax.emphasis` | Markdown |
| `link` | `syntax.link` | Markdown |

Golo produces no `heading`, `tag`, `attribute`, `emphasis` or `link` span. In `turbo-classic`, `syntax.number` and `syntax.constant` are both magenta and `syntax.char` is the green of `syntax.string`, so `42` and `true` share a colour there and so do `'x'` and `"x"`; other themes separate them. See [how to write your own theme](../how-to/write-a-theme.md) if you want to change it.

## Golo

Hand-written, in `internal/gololang`, against GoloScript's `lexer/lexer.go` and `token/token.go`. What the lexer reads as one token, the scanner colours as one span.

**Four constructs cross a line break**, and are carried to the next line exactly as the lexer reads them: a `----` block comment to its closing `----`; a `"…"` string to its closing quote; a `"""…"""` multi-line string to its closing three quotes; a `'…'` character literal to its closing apostrophe. None of the four nests. So an unterminated string colours the rest of the file, until a quote — which is what the interpreter reads it as.

| Recognised | As |
| --- | --- |
| `and`, `augment`, `augmentation`, `await`, `break`, `case`, `catch`, `continue`, `else`, `finally`, `for`, `foreach`, `function`, `if`, `import`, `in`, `is`, `isnt`, `let`, `local`, `match`, `module`, `not`, `oftype`, `or`, `orIfNull`, `otherwise`, `return`, `spawn`, `struct`, `then`, `throw`, `try`, `union`, `var`, `when`, `while`, `with` | keyword |
| `true`, `false`, `null` | constant |
| the interpreter's 157 builtins — `println`, `print`, `str`, `len`, `list`, `map`, `set`, `array`, `vector`, `range`, `readFile`, `toJSON`, `fromJSON`, `httpGet`, `DynamicObject`, … | builtin |
| any other name starting with an ASCII capital — `Point`, `Shape`, `Circle`, `Result_Failure`, `Some` | type |
| the dotted path after `module` or `import``hello.World`, `gololang.Errors`, `java.util.List` — as one span | type |
| the name after `function``main` in `function main = \|args\|` | function |
| any other lower-case name immediately before `(` | function |
| any other name: any Unicode letter or mark, `_`, or an emoji, then letters, digits and the same — `x`, `été`, `名前`, `😀`, `🚀launch` | identifier |
| `"…"` with `\n \t \r \\ \" \' \0 \xHH` escapes, across lines | string |
| `"""…"""`, across lines, no escapes | string |
| `'…'` with the same escapes, across lines | char |
| `42`, `3.14`, `1.5e-3`, `2E10`, `42L`, `3.14F`, `2.0f` | number |
| `#` to the end of the line, a shebang included | comment |
| `----``----`, across lines | comment |
| `..`, `...` | operator |
| runs of `+-*/%=<>!&\|^~?:` — including `->`, `?:`, `==`, `!=`, `<=`, `>=` | operator |
| `()[]{},;` and a lone `.` | punctuation |
| `$` in `augment Shape$Circle` | punctuation |

**A point joins a number only when a digit follows it.** That is the lexer's own test, and it is what keeps `1..3` a number and a range rather than the double `1.` and a stray `.3`.

**An exponent may have no digits.** The lexer reads `1e` as a float and leaves the parser to complain, so `1e` is one number span.

**A capitalised name is a type by convention, not by rule.** Golo lets you write `let Count = 1`, and it is coloured as a type all the same. Structs, unions, variants and augmentation targets are what people capitalise, and the colour follows the people.

**`Some`, `None`, `Ok` and `Err` are types, not constants.** They are variants of ordinary unions declared in `gololang.Errors`, available after an `import`, not builtins.

**`DynamicObject` is a builtin, capital and all.** It is in the interpreter's table, and the table wins over the case rule.

**Names may hold any Unicode letter, and emoji.** The lexer's `isLetter` admits letters, marks, `_` and four emoji blocks (emoticons, miscellaneous symbols and pictographs, transport and map symbols, supplemental symbols and pictographs); the scanner uses the same rule.

**Colouring follows the lexer, not the parser.** GoloScript's parser, as of v0.1.1, refuses several tokens its lexer reads: the `L`, `F` and `f` suffixes, a `'c'` character literal, the `..` range, `orIfNull`, `oftype` and `local function`. They are coloured as the lexer reads them, and the language server marks the line when the parser refuses it. `demos/syntax-tour/lexer-only.golo` holds one of each.

**Not recognised**, each for a stated reason:

| Not recognised | Because |
| --- | --- |
| `1_000` as one number | The lexer has no digit separator: `_` starts a name, so this is `1` and then `_000` |
| `0xFF`, `0b1010`, `0o17` as numbers | The lexer has no base prefixes: `0xFF` is `0` and then the name `xFF` |
| `.5` as a number | The lexer requires a digit before the point, so this is a dot and then `5` |
| `42l` as a long | The lexer accepts only the upper-case `L`, so this is `42` and the name `l` |
| `---` as a comment | Four dashes open a block comment; three are an operator run |
| A keyword after `:` as a method name | `obj: match()` keeps `match` a keyword — the scanner does not track what a colon introduces |
| An escape inside `"""…"""` | The lexer appends every rune until the three quotes, so `"""a\"""` ends at its first `"""` |
| A constructor as anything but a type | Nothing in the syntax separates `Circle(1.0)` from a type applied to arguments |
| An unterminated string stopping at its line | The interpreter reads to the closing quote wherever it is, so the colour follows it — the opposite of Turbo MoonBit's decision, for the opposite reason |
| Whether a name is bound in this scope | Nothing here reads more than one line at a time; that is the language server's question, and [F1 answers it](../how-to/ask-about-code.md) |

## TOML

| Recognised | As |
| --- | --- |
| `# comment` | comment |
| `[table]`, `[[array]]` | the name as a type, the brackets as punctuation |
| `key =` | identifier, then operator |
| `"basic"`, `'literal'`, `"""multi-line"""`, `'''multi-line'''` | string |
| `true`, `false` | constant |
| numbers, dates, times, `inf`, `nan` | number |

## YAML

A compose file, a Kubernetes manifest and a CI workflow are all this: there is no separate dialect, because a dialect would be somebody else's schema to keep in step with.

| Recognised | As |
| --- | --- |
| `# comment` | comment |
| `key:` before a space or the end of the line | the key as an identifier, the colon as punctuation |
| `"quoted": 1`, `'quoted': 1` | the quoted key as an identifier |
| `- ` opening a sequence entry | punctuation |
| `"…"`, `'…'` | string |
| `true`, `false`, `yes`, `no`, `on`, `off`, `null` | constant, whatever their case |
| numbers, dates and times written without quotes | number |
| `&anchor`, `*alias` | builtin |
| `!!str`, `!Custom` | type |
| `---`, `...` | the whole line as punctuation |
| `{`, `}`, `[`, `]`, `,` | punctuation |
| `\|`, `>`, with their chomping and indentation indicators | the header as an operator, the body as a string |

**A colon is a separator only when a space or the end of the line follows it.** `image: nginx:1.27` is a key and one value, and `url: http://example.com/x` is a key and one URL — colouring the inner colons as separators would put every image tag and every URL in three colours.

**A block scalar's extent is decided by indentation**, not by a delimiter. The first content line after `|` or `>` fixes the block's indentation; every line indented at least that far belongs to it, and the first line that is not ends it. **A blank line inside a block stays inside it**: a literal scalar keeps its empty lines, and ending the block at the first paragraph break would cut a shell script in a CI file in half.

**A `#` needs a space before it to start a comment**, so `colour: ff#00aa` is one scalar.

| Not recognised | Because |
| --- | --- |
| The schema of a compose file, a manifest or a workflow | Colouring `services:` differently from any other key means carrying somebody else's schema, and it goes stale the day they add a key |
| Multi-document streams as separate documents | `---` is coloured, but nothing is reset at it; nothing in the colouring depends on document boundaries |
| Whether a bare word is a string or a number to a parser | `1.2.3` is a version to a reader and a string to YAML; the scanner colours what it looks like |

## Markdown

| Recognised | As |
| --- | --- |
| `# Heading``###### Heading` | the whole line as a heading |
| `**bold**`, `__bold__`, `*italic*`, `_italic_` | emphasis |
| `` `code` `` | string |
| `[text](target)`, `![alt](src)` | the whole thing as a link |
| `- `, `* `, `+ `, `1. `, `1) ` | the marker as punctuation |
| `>` | punctuation |
| `---`, `***`, `___` | punctuation |
| ` ``` ` and `~~~` fences | the whole block, opening and closing lines included, as a string |

A fenced block is **one colour whatever language it announces**: ```` ```golo ```` does not colour its contents as Golo. The run of markers that opens a block must be matched by the same character to close it, so a backtick fence is not closed by a tilde one. An unclosed fence colours to the end of the file.

The run of markers opening emphasis must be matched by a run of the same length, so `**bold**` is one span rather than two italics.

## JavaScript

| Recognised | As |
| --- | --- |
| `const`, `let`, `function`, `class`, `async`, `await`, `import`, `export`, … | keyword |
| `true`, `false`, `null`, `undefined`, `NaN`, `Infinity`, `this` | constant |
| `console`, `document`, `window`, `Array`, `Object`, `Promise`, `Math`, `JSON`, … | builtin |
| a name immediately before `(` | function |
| `"…"`, `'…'` | string |
| `` `` ``, interpolations included, across lines | string |
| `//` to end of line, `/* … */` across lines | comment |
| `42`, `3.14`, `0x1f`, `0b1010`, `0o777`, `1_000_000`, `1e6`, `10n` | number |
| runs of `+-*/%=<>!&|^~?:` | operator |
| `()[]{},;.` | punctuation |

**Regular-expression literals are not recognised.** Telling `/x/g` from a division needs to know whether the previous token could end an expression; a wrong guess colours the rest of a line as a string, which is worse than leaving a regex the colour of an operator.

Globals are recognised by name, so a file that shadows `Math` still has it coloured as a builtin — the same rule Golo's builtins follow here.

## HTML

| Recognised | As |
| --- | --- |
| `<tag`, `</tag`, `>`, `/>` | tag |
| attribute names, including `data-*`, `xlink:href`, `@click`, `v-bind.prop` | attribute |
| `=` | operator |
| `"…"`, `'…'` | string |
| `<!-- … -->`, across lines | comment |
| `&amp;`, `&#169;` | constant |
| `<!DOCTYPE …>` and other declarations | keyword |

Text between tags is not coloured. A bare `&` with no `;` within 32 characters is left alone, because it is legal text.

**The contents of `<script>` and `<style>` are not coloured** as JavaScript and CSS.

## XML

Its own scanner rather than HTML's, for one reason that matters: CDATA. The whole point of `<![CDATA[ … ]]>` is that its contents are *not* markup, and colouring the tags inside one as tags is exactly backwards.

| Recognised | As |
| --- | --- |
| `<?xml version="1.0"?>` and other processing instructions | the target and `?>` as keyword, the pairs between as attributes and strings |
| `<!DOCTYPE …>` and the other `<!` forms | keyword |
| `<!-- … -->`, across lines | comment |
| `<![CDATA[ … ]]>`, across lines | string |
| `<tag`, `</tag`, `>`, `/>` | tag |
| `<ns:tag>`, `xsi:type` | the prefix and the local name as **one** span |
| attribute names | attribute |
| `=` | operator |
| `"…"`, `'…'` | string |
| `&amp;`, `&#169;` | constant |

**A comment and a CDATA section close on different delimiters**, and are carried separately: a `-->` inside a CDATA section does not end it.

**A bare `&` with no semicolon within 32 characters is left alone**, because it is legal text in plenty of documents and swallowing the rest of the line would be the bigger mistake.

Text between tags is not coloured.

## Shell

Applies to `sh`, `bash` and `zsh` alike: the keywords recognised are the ones they share.

| Recognised | As |
| --- | --- |
| `if`, `then`, `fi`, `for`, `while`, `case`, `esac`, `function`, `return`, … | keyword |
| `true`, `false` | constant |
| `echo`, `printf`, `export`, `local`, `read`, `cd`, `set`, `source`, … | builtin |
| `$NAME`, `${…}`, `$(…)`, `$1`, `$?`, `$@` | builtin |
| the **first bare word on a line** | function |
| every later bare word, and `NAME` in `NAME=value` | identifier |
| `'…'`, with nothing escaped or expanded inside | string |
| `"…"`, with the expansions inside it coloured as expansions | string |
| `#` to end of line | comment |

`$(a $(b) c)` is one span: nesting is counted. An option such as `-euo` is one word, not a minus and a word.

**Heredocs are not recognised.** `<<EOF` and the text after it are coloured as ordinary shell.

## Dockerfile

| Recognised | As |
| --- | --- |
| `FROM`, `RUN`, `COPY`, `ADD`, `ARG`, `ENV`, `CMD`, `ENTRYPOINT`, `EXPOSE`, `LABEL`, `USER`, `VOLUME`, `WORKDIR`, `HEALTHCHECK`, `ONBUILD`, `SHELL`, `STOPSIGNAL`, `MAINTAINER` | keyword, in any case |
| `AS`, `NONE` | keyword |
| `# comment`, including the `# syntax=` and `# escape=` directives | comment |
| `--from=builder`, `--chown=me:me` | the flag name as an attribute |
| `$NAME`, `${NAME}`, `${NAME:-default}` | builtin, as one span to the closing brace |
| `"…"`, `'…'` | string |
| a trailing `\` | operator |
| numbers | number |
| paths and image references — `/usr/local/bin`, `golang:1.26-alpine` | identifier, as **one** span |

**Only the first word of a line can be an instruction**, and a word that is not one is an argument — which is what keeps a continuation line's first word out of the keyword colour.

**Nothing crosses a line break.** A `\` joins two lines for Docker, but each half still reads as a command and is coloured on its own.

| Not recognised | Because |
| --- | --- |
| The shell inside a `RUN` | It would mean running the shell scanner over part of a line and mapping its columns out, and `RUN` may hold any language |
| Heredocs in a `RUN` | The same reason the shell scanner does not recognise them |
| Which stage a `--from` names | Nothing here reads the rest of the file |

## See also

- [Theme file format](themes.md) — every key these classes resolve to
- [Colouring and completion](../explanation/colouring-and-completion.md) — why the scanners are written this way
- [How to write your own theme](../how-to/write-a-theme.md)