Syntax Definitions¶

Syntax definitions make Sublime Text aware of programming and markup languages. Most noticeably, they work together with colors to provide syntax highlighting. Syntax definitions define scopes in a buffer that divide the text in named regions. Several editing features in Sublime Text make extensive use of this fine-grained contextual information.

Essentially, syntax definitions consist of regular expressions used to find text, and more or less arbitrary, dot-separated strings called scopes or scope names. For every occurrence of a given regular expression, Sublime Text gives the matching text its corresponding scope name.

Prerequisites¶

In order to follow this tutorial, you will need to install AAAPackageDev, a package intended to ease the creation of new syntax definitions for Sublime Text. AAAPackageDev lives on a public Mercurial repository at Bitbucket.

Download the latest .sublime-package file and double click on it if you’re running a full installation of Sublime Text, or perform a manual installation as described in Installation of .sublime-package Files.

File format¶

Sublime uses property list files (Plist) to store syntax definitions. Because editing XML files is a cumbersome task, though, we’ll be using JSON instead and converting it to Plist afterwards. This is where the AAAPackageDev package mentioned above comes in.

Note

If you experience unexpected errors during this tutorial, chances are AAAPackageDev is to blame. Don’t immediately think your problem is due to a bug in Sublime Text.

By all means, do edit the Plist files by hand if you prefer to work in XML, but keep always in mind the differing needs with regards to escape sequences, etc.

Scopes¶

Scopes are a key concept in Sublime Text. Essentially, they are named text regions in a buffer. They don’t do anything by themselves, but Sublime Text peeks at them when it needs contextual information.

For instance, when you trigger a snippet, Sublime Text checks the scope the snippet’s bound to and looks at the caret’s position in the file. If the caret’s current scope matches the snippet’s scope selector, Sublime Text fires the snippet off. Otherwise, nothing happens.

Scopes can be nested to allow for a high degree of granularity. You can drill down the hierarchy very much like with CSS selectors. For instance, thanks to scope selectors, you could have a key binding activated only within single quoted strings in python source code, but not inside single quoted strings in any other language.

Sublime Text implements the idea of scopes from Texmate, a text editor for Mac. Textmate’s online manual contains further information about scope selectors that’s useful for Sublime Text users too.

How Syntax Definitions Work¶

At their core, syntax definitions are arrays of regular expressions paired with scope names. Sublime Text will try to match these patterns against a buffer’s text and attach the corresponding scope name to all occurrences. These pairs of regular expressions and scope names are known as rules.

Rules are applied in order, one line at a time. Each rule consumes the matched text region, which will therefore be excluded from the next rule’s matching attempt (save for a few exceptions). In practical terms, this means that you should take care to go from more specific rules to more general ones when you create a new syntax definition. Otherwise, a greedy regular expression might swallow parts you’d like to have styled differently.

Syntax definitions from separate files can be combined, and they can be recursively applied too.

Your First Syntax Definition¶

By way of example, let’s create a syntax definition for Sublime Text snippets. We’ll be styling the actual snippet content, not the .sublime-snippet file.

Note

Since syntax definitions are primarily used to enable syntax highlighting, we’ll use to style as in to break down a source code file into scopes. Keep in mind, however, that colors are a different thing to syntax definitions and that scopes have many more uses besides syntax highlighting.

These are the elements we want to style in a snippet:

Variables ($PARAM1, $USER_NAME…)

Simple fields ($0, $1…)

Complex fields with place holders (${1:Hello})

Nested fields (${1:Hello ${2:World}!})

Escape sequences (\\$, \\<…)

Illegal sequences ($, <…)

Note

Before continuing, make sure you’ve installed the AAAPackageDev package as explained further above.

Creating A New Syntax Definition¶

To create a new syntax definition, follow these steps:

Go to Tools | Packages | Package Development | New Syntax Definition

Save the new file to your Packages/User folder as Sublime Snippets (Raw).JSON-tmLanguage.

You should now see a file like this:

{ "name": "Syntax Name",
  "scopeName": "source.syntax_name",
  "fileTypes": [""],
  "patterns": [
  ],
  "uuid": "ca03e751-04ef-4330-9a6b-9b99aae1c418"
}

Let’s examine now the key elements.

uuid: Located at the end, this is a unique identifier for this syntax definition. Each new syntax definition gets its own uuid. Don’t modify them.
name: The name that Sublime Text will display in the syntax definition drop-down list Use a short, descriptive name. Typically, you will be using the programming language’s name you are creating the syntax definition for.
scopeName: The top level scope for this syntax definition. It takes the form source.<lang_name> or text.<lang_name>. For programming languages, use source. For markup and everything else, text.
fileTypes: This is a list of file extensions. When opening files of these types, Sublime Text will automatically activate this syntax definition for them.
patterns: Container for your patterns.

For our example, fill in the template with the following information:

{   "name": "Sublime Snippet (Raw)",
    "scopeName": "source.ssraw",
    "fileTypes": ["ssraw"],
    "patterns": [
    ],
    "uuid": "ca03e751-04ef-4330-9a6b-9b99aae1c418"
}

Note

JSON is a very strict format, so make sure to get all the commas and quotes right. If the conversion to Plist fails, take a look at the output panel for more information on the error. We’ll explain later how to convert a syntax definition in JSON to Plist.

Analyzing Patterns¶

The patterns array can contain several types of elements. We’ll look at some of them in the following sections. If you want to learn more about patterns, refer to Textmate’s online manual.

Matches¶

They take this form:

{ "match": "[Mm]y \s+[Rr]egex",
  "name": "string.ssraw",
  "comment": "This comment is optional."
}

match: A regular expression Sublime Text will use to try and find matches.
name: Name of the scope that should be applied to the occurrences of match.
comment: An optional comment about this pattern.

Let’s go back to our example. Make it look like this:

{ "name": "Sublime Snippet (Raw)",
  "scopeName": "source.ssraw",
  "fileTypes": ["ssraw"],
  "patterns": [
  ],
  "uuid": "ca03e751-04ef-4330-9a6b-9b99aae1c418"
}

That is, make sure the patterns array is empty.

Now we can begin to add our rules for Sublime snippets. Let’s start with simple fields. These could be matched with a regex like so:

\$[0-9]+
# or...
\$\d+

However, because we’re writing our regex in JSON, we need to factor in JSON’s own escaping rules. Thus, our previous example becomes:

\\$\\d+

With escaping out of the way, we can build our pattern like this:

{ "match": "\\$\\d+",
  "name": "keyword.source.ssraw",
  "comment": "Tab stops like $1, $2..."
}

Naming scopes isn’t obvious sometimes. Check the Textmate online manual for guidance on scope names. It is important to re-use the basic categories outlined there if you want to achieve the highest compatibility with existing colors.

Colors have hardcoded scope names in them. They could not possibly include every scope name you can think of, so they target the standard ones plus some rarer ones on occasion. This means that two colors using the same syntax definition may render the text differently!

Bear in mind too that you should use the scope name that best suits your needs or preferences. It’d be perfectly fine to assign a scope like constant.numeric to anything other than a number if you have a good reason to do so.

And we can add it to our syntax definition too:

{   "name": "Sublime Snippet (Raw)",
    "scopeName": "source.ssraw",
    "fileTypes": ["ssraw"],
    "patterns": [
        { "match": "\\$\\d+",
          "name": "keyword.source.ssraw",
          "comment": "Tab stops like $1, $2..."
        }
    ],
    "uuid": "ca03e751-04ef-4330-9a6b-9b99aae1c418"
}

We’re now ready to convert our file to .tmLanguage. Syntax definitions use Textmate’s .tmLanguage extension for compatibility reasons. As explained further above, they are simply XML files in the Plist format.

Follow these steps to perform the conversion:

Select Json to tmLanguage in Tools | Build System

Press F7

A .tmLanguage file will be generated for you in the same folder as your .JSON-tmLanguage file

Restart Sublime Text so all your changes can take effect

Note

Sublime Text cannot reload syntax definitions automatically upon their modification.

You have now created your first syntax definition. Next, open a new file and save it with the extension .ssraw. The buffer’s syntax name should switch to “Sublime Snippet (Raw)” automatically, and you should get syntax highlighting if you type $1 or any other simple snippet field.

Let’s proceed to creating another rule for environment variables.

{ "match": "\\$[A-Za-z][A-Za-z0-9_]+",
  "name": "keyword.source.ssraw",
  "comment": "Variables like $PARAM1, $TM_SELECTION..."
}

Repeat the steps above to update the .tmLanguage file and restart Sublime Text.

Fine Tuning Matches¶

You might have noticed that the entire text in $PARAM1, for instance, is styled the same way. Depending on your needs or your personal preferences, you may want the $ to stand out. That’s where captures come in. Using captures, you can break a pattern down into components to target them individually.

Let’s rewrite one of our previous patterns to use captures:

{ "match": "\\$([A-Za-z][A-Za-z0-9_]+)",
  "name": "keyword.ssraw",
  "captures": {
      "1": { "name": "constant.numeric.ssraw" }
   },
  "comment": "Variables like $PARAM1, $TM_SELECTION..."
}

Captures introduce complexity to your rule, but they are pretty straightforward. Notice how numbers refer to parenthesized groups left to right. Of course, you can have as many capture groups as you want.

Arguably, you’d want the other scope to be visually consistent with this one. Go ahead and change it too.

Begin-End Rules¶

Up to now we’ve been using a simple rule. Although we’ve seen how to dissect patterns into smaller components, sometimes you’ll want to target a larger portion of your source code clearly delimited by start and end marks.

Literal strings enclosed in quotation marks and other delimited constructs are better dealt with with begin-end rules. This is a skeleton for one of these rules:

{ "name": "",
  "begin": "",
  "end": ""
}

Well, at least in their simplest version. Let’s take a look at one including all available options:

{ "name": "",
  "begin": "",
  "beginCaptures": {
    "0": { "name": "" }
  },
  "end": "",
  "endCaptures": {
    "0": { "name": "" }
  },
  "patterns": [
     {  "name": "",
        "match": ""
                  }
  ],
  "contentName": ""
}

Some elements may look familiar, but their combination might be daunting. Let’s see them individually.

begin: Regex for the opening mark for this scope.
end: Regex for the end mark for this scope.
beginCaptures: Captures for the begin marker. They work like captures for simple matches. Optional.
endCaptures: Same as beginCaptures but for the end marker. Optional.
contentName: Scope for the whole matched region, from the begin marker to the end marker, inclusive. This will effectively create nested scopes for beginCaptures, endCaptures and patterns defined within this rule. Optional.
patterns: An array of patterns to match against the begin-end content only —they are not matched against the text consumed by begin or end.

We’ll use this rule to style nested complex fields in snippets:

{ "name": "variable.complex.ssraw",
   "begin": "(\\$)(\\{)([0-9]+):",
   "beginCaptures": {
       "1": { "name": "keyword.ssraw" },
       "3": { "name": "constant.numeric.ssraw" }
   },
   "patterns": [
       { "include": "$self" },
       {  "name": "string.ssraw",
          "match": "."
       }
   ],
   "end": "\\}"
}

This is the most complex pattern we’ll see in this tutorial. The begin and end keys are self-explanatory: they define a region enclosed between ${<NUMBER>: and }. beginCaptures further divides the begin mark into smaller scopes.

The most interesting part, however, is patterns. Recursion and the importance of ordering have finally made an appearance here.

We’ve seen further above that fields can be nested. In order to account for this, we need to recursively style nested fields. That’s what the include rule does when furnished the $self value: it recursively applies our entire syntax definition to the portion of text contained in our begin-end rule, excluding the text consumed by both begin and end.

Remember that matched text is consumed and is excluded from the next match attempt.

To finish off complex fields, we’ll style place holders as strings. Since we’ve already matched all possible tokens inside a complex field, we can safely tell Sublime Text to give any remaining text (.) a literal string scope.

Final Touches¶

Lastly, let’s style escape sequences and illegal sequences, and wrap up.

{  "name": "constant.character.escape.ssraw",
   "match": "\\\\(\\$|\\>|\\<)"
},

{  "name": "invalid.ssraw",
   "match": "(\\$|\\<|\\>)"
}

The only hard thing here is getting the number of escape characters right. Other than that, the rules are pretty straightforward if you’re familiar with regular expressions.

However, you must take care to put the second rule after any others matching the $ character, since otherwise you may not get the desired result.

Also, note that after adding these two additional rules, our recursive begin-end rule above keeps working as expected.

At long last, here’s the final syntax definition:

{   "name": "Sublime Snippet (Raw)",
    "scopeName": "source.ssraw",
    "fileTypes": ["ssraw"],
    "patterns": [
        { "match": "\\$(\\d+)",
          "name": "keyword.ssraw",
          "captures": {
              "1": { "name": "constant.numeric.ssraw" }
           },
          "comment": "Tab stops like $1, $2..."
        },

        { "match": "\\$([A-Za-z][A-Za-z0-9_]+)",
          "name": "keyword.ssraw",
          "captures": {
              "1": { "name": "constant.numeric.ssraw" }
           },
          "comment": "Variables like $PARAM1, $TM_SELECTION..."
        },

        { "name": "variable.complex.ssraw",
          "begin": "(\\$)(\\{)([0-9]+):",
          "beginCaptures": {
              "1": { "name": "keyword.ssraw" },
              "3": { "name": "constant.numeric.ssraw" }
           },
           "patterns": [
              { "include": "$self" },
              { "name": "string.ssraw",
                "match": "."
              }
           ],
           "end": "\\}"
        },

        { "name": "constant.character.escape.ssraw",
          "match": "\\\\(\\$|\\>|\\<)"
        },

        { "name": "invalid.ssraw",
          "match": "(\\$|\\>|\\<)"
        }
    ],
    "uuid": "ca03e751-04ef-4330-9a6b-9b99aae1c418"
}

There are more available constructs and code reuse techniques, but the above explanations should get you started with the creation of syntax definitions.