WebAssembly API Reference

WebAssembly API Reference v1.9.1¶

Functions¶

detectLanguageFromExtension()¶

Detect language name from a file extension (without leading dot).

Returns null for unrecognized extensions. The match is case-insensitive.

Signature:

function detectLanguageFromExtension(ext: string): string | null

Example:

const result = detectLanguageFromExtension("value");

Parameters:

Returns: string | null

detectLanguageFromPath()¶

Detect language name from a file path.

Extracts the file extension and looks it up. Returns null if the path has no extension or the extension is not recognized.

Signature:

function detectLanguageFromPath(path: string): string | null

Example:

const result = detectLanguageFromPath("value");

Parameters:

Returns: string | null

detectLanguageFromContent()¶

Detect language name from file content using the shebang line (#!).

Inspects only the first line of content. If it begins with #!, the interpreter name is extracted and mapped to a language name.

Handles common patterns:

• #!/usr/bin/env python3 → "python"
• #!/bin/bash → "bash"
• #!/usr/bin/env node → "javascript"

The -S flag accepted by some env implementations is skipped automatically. Version suffixes (e.g. python3.11, ruby3.2) are stripped before matching.

Returns null when content does not start with #!, the shebang is malformed, or the interpreter is not recognised.

Signature:

function detectLanguageFromContent(content: string): string | null

Example:

const result = detectLanguageFromContent("value");

Parameters:

Returns: string | null

getHighlightsQuery()¶

Get the highlights query for a language, if bundled.

Returns the contents of highlights.scm as a static string, or null if no highlights query is bundled for this language.

Signature:

function getHighlightsQuery(language: string): string | null

Example:

const result = getHighlightsQuery("value");

Parameters:

Returns: string | null

getInjectionsQuery()¶

Get the injections query for a language, if bundled.

Returns the contents of injections.scm as a static string, or null if no injections query is bundled for this language.

Signature:

function getInjectionsQuery(language: string): string | null

Example:

const result = getInjectionsQuery("value");

Parameters:

Returns: string | null

getLocalsQuery()¶

Get the locals query for a language, if bundled.

Returns the contents of locals.scm as a static string, or null if no locals query is bundled for this language.

Signature:

function getLocalsQuery(language: string): string | null

Example:

const result = getLocalsQuery("value");

Parameters:

Returns: string | null

getTagsQuery()¶

Get the tags query for a language, if bundled.

Returns the contents of tags.scm as a static string, or null if no tags query is bundled for this language.

Signature:

function getTagsQuery(language: string): string | null

Example:

const result = getTagsQuery("value");

Parameters:

Returns: string | null

getLanguage()¶

Get a tree-sitter Language by name using the global registry.

Resolves language aliases (e.g., "shell" maps to "bash"). When the download feature is enabled (default), automatically downloads the parser from GitHub releases if not found locally.

Errors:

Returns Error.LanguageNotFound if the language is not recognized, or Error.Download if auto-download fails.

Signature:

function getLanguage(name: string): Language

Example:

const result = getLanguage("value");

Parameters:

Returns: Language

Errors: Throws Error with a descriptive message.

getParser()¶

Get a Parser pre-configured for the given language.

This is a convenience function that calls get_language and configures a new parser in one step.

Errors:

Returns Error.LanguageNotFound if the language is not recognized, or Error.ParserSetup if the language cannot be applied to the parser.

Signature:

function getParser(name: string): Parser

Example:

const result = getParser("value");

Parameters:

Returns: Parser

Errors: Throws Error with a descriptive message.

detectLanguage()¶

Detect language name from a file path or extension.

This compatibility alias matches the pre-Alef Python binding API.

Signature:

function detectLanguage(path: string): string | null

Example:

const result = detectLanguage("value");

Parameters:

Returns: string | null

availableLanguages()¶

List all available language names (sorted, deduplicated, includes aliases).

Returns names of both statically compiled and dynamically loadable languages, plus any configured aliases.

Signature:

function availableLanguages(): Array<string>

Example:

const result = availableLanguages();

Returns: Array<string>

hasLanguage()¶

Check if a language is available by name or alias.

Returns true if the language can be loaded (statically compiled, dynamically available, or a known alias for one of these).

Signature:

function hasLanguage(name: string): boolean

Example:

const result = hasLanguage("value");

Parameters:

Returns: boolean

languageCount()¶

Return the number of available languages.

Includes statically compiled languages, dynamically loadable languages, and aliases.

Signature:

function languageCount(): number

Example:

const result = languageCount();

Returns: number

process()¶

Process source code and extract file intelligence using the global registry.

Parses the source with tree-sitter and extracts metrics, structure, imports, exports, comments, docstrings, symbols, diagnostics, and/or chunks based on the flags set in ProcessConfig.

Errors:

Returns an error if the language is not found or parsing fails.

Signature:

function process(source: string, config: ProcessConfig): ProcessResult

Example:

const result = process("value", new ProcessConfig());

Parameters:

Returns: ProcessResult

Errors: Throws Error with a descriptive message.

init()¶

Initialize the language pack with the given configuration.

Applies any custom cache directory, then downloads all languages and groups specified in the config. This is the recommended entry point when you want to pre-warm the cache before use.

Errors:

Returns an error if configuration cannot be applied or if downloads fail.

Signature:

function init(config: PackConfig): void

Example:

init(new PackConfig());

Parameters:

Returns: No return value.

Errors: Throws Error with a descriptive message.

configure()¶

Apply download configuration without downloading anything.

Use this to set a custom cache directory before the first call to get_language or any download function. Changing the cache dir after languages have been registered has no effect on already-loaded languages.

Errors:

Returns an error if the lock cannot be acquired.

Signature:

function configure(config: PackConfig): void

Example:

configure(new PackConfig());

Parameters:

Returns: No return value.

Errors: Throws Error with a descriptive message.

download()¶

Download specific languages to the local cache.

Returns the number of requested languages available after the call. Already compiled or cached languages are included in the count.

Errors:

Returns an error if any language is not available in the manifest or if the download fails.

Signature:

function download(names: Array<string>): number

Example:

const result = download([]);

Parameters:

Returns: number

Errors: Throws Error with a descriptive message.

downloadAll()¶

Download all available languages from the remote manifest.

Downloads the platform bundle and extracts every library it contains. Languages that appear in the manifest but are absent from the bundle (e.g. grammars that failed to compile at release time) are silently skipped — they are not treated as an error.

Returns the total number of languages now available (statically compiled plus downloaded and cached).

Errors:

Returns an error if the manifest cannot be fetched or the bundle download fails.

Signature:

function downloadAll(): number

Example:

const result = downloadAll();

Returns: number

Errors: Throws Error with a descriptive message.

downloadGroup()¶

Download every language in a named group (e.g. "web", "data").

Groups are defined in the remote manifest and let you ensure a curated set of related grammars in one call instead of listing each name to download(). Already-cached languages are skipped.

Returns the total number of languages now available (statically compiled plus downloaded and cached).

Errors:

Returns an error if the manifest cannot be fetched, the group is unknown, or any constituent language fails to download.

Signature:

function downloadGroup(name: string): number

Example:

const result = downloadGroup("value");

Parameters:

Returns: number

Errors: Throws Error with a descriptive message.

manifestLanguages()¶

Return all language names available in the remote manifest (306).

Fetches (and caches) the remote manifest to discover the full list of downloadable languages. Use downloaded_languages to list what is already cached locally.

Errors:

Returns an error if the manifest cannot be fetched.

Signature:

function manifestLanguages(): Array<string>

Example:

const result = manifestLanguages();

Returns: Array<string>

Errors: Throws Error with a descriptive message.

downloadedLanguages()¶

Return languages that are already downloaded and cached locally.

Does not perform any network requests. Returns an empty list if the cache directory does not exist or cannot be read.

Signature:

function downloadedLanguages(): Array<string>

Example:

const result = downloadedLanguages();

Returns: Array<string>

cleanCache()¶

Delete all cached parser shared libraries.

Resets the cache registration so the next call to get_language or a download function will re-register the (now empty) cache directory.

Errors:

Returns an error if the cache directory cannot be removed.

Signature:

function cleanCache(): void

Example:

cleanCache();

Returns: No return value.

Errors: Throws Error with a descriptive message.

cacheDir()¶

Return the effective cache directory path.

This is either the custom path set via configure / init or the default: ~/.cache/tree-sitter-language-pack/v{version}/libs/.

Errors:

Returns an error if the system cache directory cannot be determined.

Signature:

function cacheDir(): string

Example:

const result = cacheDir();

Returns: string

Errors: Throws Error with a descriptive message.

Types¶

ByteRange¶

A byte range — start (inclusive) to end (exclusive).

ChunkContext¶

Metadata for a single chunk of source code.

CodeChunk¶

A chunk of source code with rich metadata.

CommentInfo¶

A comment extracted from source code.

DataAttribute¶

An XML-style attribute attached to an Element node.

Populated only for DataNodeKind.Element; always empty for KeyValue and Sequence nodes.

DataNode¶

A node in the hierarchical data tree produced by data-format extraction.

When ProcessConfig.data_extraction is true, ProcessResult.data is populated with a root DataNode whose children mirror the structure of the parsed file.

The kind field determines which other fields are meaningful:

Diagnostic¶

A diagnostic (syntax error, missing node, etc.) from parsing.

DocSection¶

A section within a docstring (e.g., Args, Returns, Raises).

DocstringInfo¶

A docstring extracted from source code.

DownloadManager¶

Manages downloading and caching of pre-built parser shared libraries.

Methods¶

new()¶

Create a new download manager for the given version.

Signature:

static new(version: string): DownloadManager

Example:

const result = DownloadManager.new("value");

Parameters:

Returns: DownloadManager

Errors: Throws Error with a descriptive message.

installedLanguages()¶

List languages that are already downloaded and cached.

Signature:

installedLanguages(): Array<string>

Example:

const result = instance.installedLanguages();

Returns: Array<string>

downloadAllBestEffort()¶

Download the platform bundle and extract every library file it contains.

Unlike Self.ensure_languages, this does not check the manifest language list against archive contents — it simply extracts all .so/.dylib/.dll files from the bundle. Languages in the manifest that are missing from the archive are silently ignored rather than returning an error.

Returns the number of library files extracted (including those already cached).

Signature:

downloadAllBestEffort(): number

Example:

const result = instance.downloadAllBestEffort();

Returns: number

Errors: Throws Error with a descriptive message.

cleanCache()¶

Remove all cached parser libraries.

Acquires the cross-process lock so clean_cache cannot race a concurrent downloader (avoids Windows sharing-violation errors against an in-flight bundle write). The .download.lock file itself is not removed — it is permanent infrastructure; deleting it could allow a concurrent process that already opened the file to continue holding a stale lock handle while a new process opens a fresh inode, breaking the mutual-exclusion guarantee.

Signature:

cleanCache(): void

Example:

instance.cleanCache();

Returns: No return value.

Errors: Throws Error with a descriptive message.

ExportInfo¶

An export statement extracted from source code.

FileMetrics¶

Aggregate metrics for a source file.

ImportInfo¶

An import statement extracted from source code.

Language¶

LanguageRegistry¶

Thread-safe registry of tree-sitter language parsers.

Manages both statically compiled and dynamically loaded language grammars. Use LanguageRegistry.new() for the default registry, or access the global instance via the module-level convenience functions (get_language, available_languages, etc.).

Methods¶

new()¶

Create a new registry populated with all statically compiled languages.

When the dynamic-loading feature is enabled, the registry also knows about dynamically loadable grammars and will load them on demand.

Signature:

static new(): LanguageRegistry

Example:

const result = LanguageRegistry.new();

Returns: LanguageRegistry

getLanguage()¶

Get a tree-sitter Language by name.

Resolves aliases (e.g., "shell" -> "bash", "makefile" -> "make"), then looks up the language in the static table. When the dynamic-loading feature is enabled, falls back to loading a shared library on demand.

Errors:

Returns Error.LanguageNotFound if the name (after alias resolution) does not match any known grammar.

Signature:

getLanguage(name: string): Language

Example:

const result = instance.getLanguage("value");

Parameters:

Returns: Language

Errors: Throws Error with a descriptive message.

availableLanguages()¶

List all available language names, sorted and deduplicated.

Includes statically compiled languages, dynamically loadable languages (if the dynamic-loading feature is enabled), and all configured aliases.

Signature:

availableLanguages(): Array<string>

Example:

const result = instance.availableLanguages();

Returns: Array<string>

hasParser()¶

Check whether a parser is statically compiled into this build.

Returns true only when the grammar was compiled in at build time (i.e. it appears in the STATIC_LANGUAGES table). This is independent of the extension-to-language mapping: detect_language_from_extension consults the static ext table for all 306 grammars regardless of which parsers are compiled in.

Use this when you need to distinguish "we know the language name" from "we can actually parse files in that language right now".

use tree_sitter_language_pack::{detect_language_from_extension, LanguageRegistry};

let registry = LanguageRegistry::new();
// Extension detection uses the static table — independent of compiled parsers.
let lang = detect_language_from_extension("feature"); // always returns Some("gherkin")
// Parser availability depends on which grammars were compiled in.
let can_parse = lang.map(|name| registry.has_parser(name)).unwrap_or(false);

Signature:

hasParser(name: string): boolean

Example:

const result = instance.hasParser("value");

Parameters:

Returns: boolean

hasLanguage()¶

Check whether a language is available by name or alias.

Returns true if the language can be loaded, either from the static table or from a dynamic library on disk.

Signature:

hasLanguage(name: string): boolean

Example:

const result = instance.hasLanguage("value");

Parameters:

Returns: boolean

languageCount()¶

Return the total number of available languages (including aliases).

Signature:

languageCount(): number

Example:

const result = instance.languageCount();

Returns: number

process()¶

Parse source code and extract file intelligence based on config in a single pass.

Signature:

process(source: string, config: ProcessConfig): ProcessResult

Example:

const result = instance.process("value", new ProcessConfig());

Parameters:

Returns: ProcessResult

Errors: Throws Error with a descriptive message.

default()¶

Signature:

static default(): LanguageRegistry

Example:

const result = LanguageRegistry.default();

Returns: LanguageRegistry

Node¶

A single syntax node within a Tree.

Nodes hold a strong reference to their parent tree so they remain valid regardless of how the tree is moved or stored at the FFI boundary.

Methods¶

clone()¶

Signature:

clone(): Node

Example:

const result = instance.clone();

Returns: Node

kind()¶

Return the node's kind name (e.g. "function_definition").

Signature:

kind(): string

Example:

const result = instance.kind();

Returns: string

kindId()¶

Return the node's numeric kind ID.

Tree-sitter assigns a stable u16 ID to every node kind in a grammar (e.g. "function_definition" → 42). Comparing kind_id() is cheaper than comparing the string kind() in tight AST loops.

Signature:

kindId(): number

Example:

const result = instance.kindId();

Returns: number

startByte()¶

Return the inclusive start byte offset of this node.

Signature:

startByte(): number

Example:

const result = instance.startByte();

Returns: number

endByte()¶

Return the exclusive end byte offset of this node.

Signature:

endByte(): number

Example:

const result = instance.endByte();

Returns: number

byteRange()¶

Return the node's byte range as a ByteRange.

Callers should slice their own source bytes — this is a zero-copy text accessor.

Signature:

byteRange(): ByteRange

Example:

const result = instance.byteRange();

Returns: ByteRange

startPosition()¶

Return the start Point (row, column).

Signature:

startPosition(): Point

Example:

const result = instance.startPosition();

Returns: Point

endPosition()¶

Return the end Point (row, column).

Signature:

endPosition(): Point

Example:

const result = instance.endPosition();

Returns: Point

isNamed()¶

True when this node is named (not punctuation/whitespace).

Signature:

isNamed(): boolean

Example:

const result = instance.isNamed();

Returns: boolean

isError()¶

True when this is an error node.

Signature:

isError(): boolean

Example:

const result = instance.isError();

Returns: boolean

isMissing()¶

True when this is a missing-token node.

Signature:

isMissing(): boolean

Example:

const result = instance.isMissing();

Returns: boolean

isExtra()¶

True when this is an "extra" node (e.g. a comment).

Signature:

isExtra(): boolean

Example:

const result = instance.isExtra();

Returns: boolean

hasError()¶

True when this node or any descendant is an error.

Signature:

hasError(): boolean

Example:

const result = instance.hasError();

Returns: boolean

parent()¶

Return this node's parent, if any.

Signature:

parent(): Node | null

Example:

const result = instance.parent();

Returns: Node | null

child()¶

Return the i-th child of this node, if any.

Signature:

child(index: number): Node | null

Example:

const result = instance.child(42);

Parameters:

Returns: Node | null

childCount()¶

Total number of children (including unnamed).

Signature:

childCount(): number

Example:

const result = instance.childCount();

Returns: number

namedChild()¶

Return the i-th named child of this node, if any.

Signature:

namedChild(index: number): Node | null

Example:

const result = instance.namedChild(42);

Parameters:

Returns: Node | null

namedChildCount()¶

Number of named children of this node.

Signature:

namedChildCount(): number

Example:

const result = instance.namedChildCount();

Returns: number

childByFieldName()¶

Look up a child by its grammar-defined field name.

Signature:

childByFieldName(name: string): Node | null

Example:

const result = instance.childByFieldName("value");

Parameters:

Returns: Node | null

toSexp()¶

Return the S-expression form of this node's subtree.

Signature:

toSexp(): string

Example:

const result = instance.toSexp();

Returns: string

walk()¶

Return a TreeCursor positioned at this node.

Signature:

walk(): TreeCursor

Example:

const result = instance.walk();

Returns: TreeCursor

PackConfig¶

Configuration for the tree-sitter language pack.

Controls cache directory and which languages to pre-download. Can be loaded from a TOML file, constructed programmatically, or passed as a dict/object from language bindings.

Parser¶

A tree-sitter parser configured for one language at a time.

Methods¶

new()¶

Construct a new parser with no language set.

Call Parser.set_language before parsing.

Signature:

static new(): Parser

Example:

const result = Parser.new();

Returns: Parser

setLanguage()¶

Configure the parser to use the language identified by name (e.g. "python").

Resolves the language through the global registry — auto-downloading if necessary, when the download feature is enabled.

Errors:

Returns Error.LanguageNotFound if the language is not recognized, or Error.ParserSetup if the language ABI is incompatible.

Signature:

setLanguage(name: string): void

Example:

instance.setLanguage("value");

Parameters:

Returns: No return value.

Errors: Throws Error with a descriptive message.

parse()¶

Parse a UTF-8 source string. Returns null if parsing was cancelled or no language is set.

Signature:

parse(source: string): Tree | null

Example:

const result = instance.parse("value");

Parameters:

Returns: Tree | null

parseBytes()¶

Parse a raw byte slice. Returns null if parsing was cancelled or no language is set.

Signature:

parseBytes(source: Buffer): Tree | null

Example:

const result = instance.parseBytes(new Uint8Array([100, 97, 116, 97]));

Parameters:

Returns: Tree | null

reset()¶

Reset internal state. The next call to parse will not be incremental.

Signature:

reset(): void

Example:

instance.reset();

Returns: No return value.

default()¶

Signature:

static default(): Parser

Example:

const result = Parser.default();

Returns: Parser

Point¶

A source position — row + column, zero-indexed.

ProcessConfig¶

Configuration for the process() function.

Controls which analysis features are enabled and whether chunking is performed.

Methods¶

default()¶

Signature:

static default(): ProcessConfig

Example:

const result = ProcessConfig.default();

Returns: ProcessConfig

withChunking()¶

Enable chunking with the given maximum chunk size in bytes.

Signature:

withChunking(maxSize: number): ProcessConfig

Example:

const result = instance.withChunking(42);

Parameters:

Returns: ProcessConfig

all()¶

Enable all analysis features.

Signature:

all(): ProcessConfig

Example:

const result = instance.all();

Returns: ProcessConfig

minimal()¶

Disable all analysis features (only metrics computed).

Signature:

minimal(): ProcessConfig

Example:

const result = instance.minimal();

Returns: ProcessConfig

withDataExtraction()¶

Enable or disable hierarchical data extraction for data-format files.

When true, ProcessResult.data is populated with a key/value tree for supported data-format languages.

Signature:

withDataExtraction(enabled: boolean): ProcessConfig

Example:

const result = instance.withDataExtraction(true);

Parameters:

Returns: ProcessConfig

ProcessResult¶

Complete analysis result from processing a source file.

Contains metrics, structural analysis, imports/exports, comments, docstrings, symbols, diagnostics, and optionally chunked code segments. Fields are populated based on the ProcessConfig flags.

Span¶

Byte and line/column range in source code.

Represents both byte offsets (for slicing) and human-readable line/column positions (for display and diagnostics).

StructureItem¶

A structural item (function, class, struct, etc.) in source code.

SymbolInfo¶

A symbol (variable, function, type, etc.) extracted from source code.

Tree¶

A parsed syntax tree. Cheap to clone (refcount bump).

Methods¶

rootNode()¶

Return the root Node of this tree.

Signature:

rootNode(): Node

Example:

const result = instance.rootNode();

Returns: Node

walk()¶

Return a TreeCursor positioned at the root.

Signature:

walk(): TreeCursor

Example:

const result = instance.walk();

Returns: TreeCursor

TreeCursor¶

A cursor for traversing a Tree.

Methods¶

node()¶

Return the Node at the cursor's current position.

Signature:

node(): Node

Example:

const result = instance.node();

Returns: Node

gotoFirstChild()¶

Move the cursor to the first child of the current node. Returns true if a child existed.

Signature:

gotoFirstChild(): boolean

Example:

const result = instance.gotoFirstChild();

Returns: boolean

gotoParent()¶

Move the cursor to the parent of the current node. Returns true if a parent existed.

Signature:

gotoParent(): boolean

Example:

const result = instance.gotoParent();

Returns: boolean

gotoNextSibling()¶

Move the cursor to the next sibling of the current node. Returns true if a sibling existed.

Signature:

gotoNextSibling(): boolean

Example:

const result = instance.gotoNextSibling();

Returns: boolean

fieldName()¶

Return the field name for the current node, if any.

Signature:

fieldName(): string | null

Example:

const result = instance.fieldName();

Returns: string | null

Enums¶

DataNodeKind¶

The kind of a data node extracted from a data-format file.

Classifies each node in the hierarchical DataNode tree returned when data_extraction is enabled on ProcessConfig.

Wire format (public JSON contract)¶

Unit variants serialize as a bare string ("KeyValue"). DO NOT add #[serde(tag = "...")] or rename variants — every language binding has a hand-written deserializer matching this exact shape, and any change breaks all bindings' process() tests simultaneously. Covered by tests/wire_format.rs.

StructureKind¶

The kind of structural item found in source code.

Categorizes top-level and nested declarations such as functions, classes, structs, enums, traits, and more. Use Other for language-specific constructs that do not fit a standard category.

Wire format (public JSON contract)¶

Unit variants serialize as a bare string ("Function"); the Other variant serializes as a single-keyed object ({"Other": "macro"}). DO NOT add #[serde(tag = "...")] or rename variants — every language binding has a hand-written deserializer matching this exact shape, and any change breaks all bindings' process() tests simultaneously. Covered by tests/wire_format.rs.

CommentKind¶

The kind of a comment found in source code.

Distinguishes between single-line comments, block (multi-line) comments, and documentation comments.

DocstringFormat¶

The format of a docstring extracted from source code.

Identifies the docstring convention used, which varies by language (e.g., Python triple-quoted strings, JSDoc, Rustdoc /// comments).

Wire format (public JSON contract)¶

Unit variants serialize as a bare string ("JSDoc"); the Other variant serializes as a single-keyed object ({"Other": "rst"}). DO NOT add #[serde(tag = "...")]. Covered by tests/wire_format.rs.

ExportKind¶

The kind of an export statement found in source code.

Covers named exports, default exports, and re-exports from other modules.

SymbolKind¶

The kind of a symbol definition found in source code.

Categorizes symbol definitions such as variables, constants, functions, classes, types, interfaces, enums, and modules.

Wire format (public JSON contract)¶

Unit variants serialize as a bare string ("Function"); the Other variant serializes as a single-keyed object ({"Other": "macro"}). DO NOT add #[serde(tag = "...")]. Covered by tests/wire_format.rs.

DiagnosticSeverity¶

Severity level of a diagnostic produced during parsing.

Used to classify parse errors, warnings, and informational messages found in the syntax tree.

Errors¶

Error¶

Errors that can occur when using the tree-sitter language pack.

Covers language lookup failures, parse errors, query errors, and I/O issues. Feature-gated variants are included when config, download, or related features are enabled.

Errors are thrown as plain Error objects with descriptive messages.

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