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<title>Using Parser (GNU Emacs Lisp Reference Manual)</title>
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<div class="section" id="Using-Parser">
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<p>
Next: <a href="Retrieving-Node.html" accesskey="n" rel="next">Retrieving Node</a>, Previous: <a href="Language-Definitions.html" accesskey="p" rel="prev">Tree-sitter Language Definitions</a>, Up: <a href="Parsing-Program-Source.html" accesskey="u" rel="up">Parsing Program Source</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index.html" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<span id="Using-Tree_002dsitter-Parser"></span><h3 class="section">37.2 Using Tree-sitter Parser</h3>
<span id="index-Tree_002dsitter-parser"></span>
<p>This section described how to create and configure a tree-sitter
parser. In Emacs, each tree-sitter parser is associated with a
buffer. As we edit the buffer, the associated parser and the syntax
tree is automatically kept up-to-date.
</p>
<dl class="def">
<dt id="index-treesit_002dmax_002dbuffer_002dsize"><span class="category">Variable: </span><span><strong>treesit-max-buffer-size</strong><a href='#index-treesit_002dmax_002dbuffer_002dsize' class='copiable-anchor'> ¶</a></span></dt>
<dd><p>This variable contains the maximum size of buffers in which
tree-sitter can be activated. Major modes should check this value
when deciding whether to enable tree-sitter features.
</p></dd></dl>
<dl class="def">
<dt id="index-treesit_002dcan_002denable_002dp"><span class="category">Function: </span><span><strong>treesit-can-enable-p</strong><a href='#index-treesit_002dcan_002denable_002dp' class='copiable-anchor'> ¶</a></span></dt>
<dd><p>This function checks whether the current buffer is suitable for
activating tree-sitter features. It basically checks
<code>treesit-available-p</code> and <code>treesit-max-buffer-size</code>.
</p></dd></dl>
<span id="index-Creating-tree_002dsitter-parsers"></span>
<dl class="def">
<dt id="index-treesit_002dparser_002dcreate"><span class="category">Function: </span><span><strong>treesit-parser-create</strong> <em>language &optional buffer no-reuse</em><a href='#index-treesit_002dparser_002dcreate' class='copiable-anchor'> ¶</a></span></dt>
<dd><p>To create a parser, we provide a <var>buffer</var> and the <var>language</var>
to use (see <a href="Language-Definitions.html">Tree-sitter Language Definitions</a>). If <var>buffer</var> is nil, the
current buffer is used.
</p>
<p>By default, this function reuses a parser if one already exists for
<var>language</var> in <var>buffer</var>, if <var>no-reuse</var> is non-nil, this
function always creates a new parser.
</p></dd></dl>
<p>Given a parser, we can query information about it:
</p>
<dl class="def">
<dt id="index-treesit_002dparser_002dbuffer"><span class="category">Function: </span><span><strong>treesit-parser-buffer</strong> <em>parser</em><a href='#index-treesit_002dparser_002dbuffer' class='copiable-anchor'> ¶</a></span></dt>
<dd><p>Returns the buffer associated with <var>parser</var>.
</p></dd></dl>
<dl class="def">
<dt id="index-treesit_002dparser_002dlanguage"><span class="category">Function: </span><span><strong>treesit-parser-language</strong> <em>parser</em><a href='#index-treesit_002dparser_002dlanguage' class='copiable-anchor'> ¶</a></span></dt>
<dd><p>Returns the language that <var>parser</var> uses.
</p></dd></dl>
<dl class="def">
<dt id="index-treesit_002dparser_002dp"><span class="category">Function: </span><span><strong>treesit-parser-p</strong> <em>object</em><a href='#index-treesit_002dparser_002dp' class='copiable-anchor'> ¶</a></span></dt>
<dd><p>Checks if <var>object</var> is a tree-sitter parser. Return non-nil if it
is, return nil otherwise.
</p></dd></dl>
<p>There is no need to explicitly parse a buffer, because parsing is done
automatically and lazily. A parser only parses when we query for a
node in its syntax tree. Therefore, when a parser is first created,
it doesn’t parse the buffer; it waits until we query for a node for
the first time. Similarly, when some change is made in the buffer, a
parser doesn’t re-parse immediately.
</p>
<span id="index-treesit_002dbuffer_002dtoo_002dlarge"></span>
<p>When a parser do parse, it checks for the size of the buffer.
Tree-sitter can only handle buffer no larger than about 4GB. If the
size exceeds that, Emacs signals <code>treesit-buffer-too-large</code>
with signal data being the buffer size.
</p>
<p>Once a parser is created, Emacs automatically adds it to the
internal parser list. Every time a change is made to the buffer,
Emacs updates parsers in this list so they can update their syntax
tree incrementally.
</p>
<dl class="def">
<dt id="index-treesit_002dparser_002dlist"><span class="category">Function: </span><span><strong>treesit-parser-list</strong> <em>&optional buffer</em><a href='#index-treesit_002dparser_002dlist' class='copiable-anchor'> ¶</a></span></dt>
<dd><p>This function returns the parser list of <var>buffer</var>. And
<var>buffer</var> defaults to the current buffer.
</p></dd></dl>
<dl class="def">
<dt id="index-treesit_002dparser_002ddelete"><span class="category">Function: </span><span><strong>treesit-parser-delete</strong> <em>parser</em><a href='#index-treesit_002dparser_002ddelete' class='copiable-anchor'> ¶</a></span></dt>
<dd><p>This function deletes <var>parser</var>.
</p></dd></dl>
<span id="index-tree_002dsitter-narrowing"></span>
<span id="tree_002dsitter-narrowing"></span><p>Normally, a parser “sees” the whole
buffer, but when the buffer is narrowed (see <a href="Narrowing.html">Narrowing</a>), the
parser will only see the visible region. As far as the parser can
tell, the hidden region is deleted. And when the buffer is later
widened, the parser thinks text is inserted in the beginning and in
the end. Although parsers respect narrowing, narrowing shouldn’t be
the mean to handle a multi-language buffer; instead, set the ranges in
which a parser should operate in. See <a href="Multiple-Languages.html">Parsing Text in Multiple Languages</a>.
</p>
<p>Because a parser parses lazily, when we narrow the buffer, the parser
is not affected immediately; as long as we don’t query for a node
while the buffer is narrowed, the parser is oblivious of the
narrowing.
</p>
<span id="index-tree_002dsitter-parse-string"></span>
<dl class="def">
<dt id="index-treesit_002dparse_002dstring"><span class="category">Function: </span><span><strong>treesit-parse-string</strong> <em>string language</em><a href='#index-treesit_002dparse_002dstring' class='copiable-anchor'> ¶</a></span></dt>
<dd><p>Besides creating a parser for a buffer, we can also just parse a
string. Unlike a buffer, parsing a string is a one-time deal, and
there is no way to update the result.
</p>
<p>This function parses <var>string</var> with <var>language</var>, and returns the
root node of the generated syntax tree.
</p></dd></dl>
</div>
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Next: <a href="Retrieving-Node.html">Retrieving Node</a>, Previous: <a href="Language-Definitions.html">Tree-sitter Language Definitions</a>, Up: <a href="Parsing-Program-Source.html">Parsing Program Source</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index.html" title="Index" rel="index">Index</a>]</p>
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