WebAssembly API Reference

WebAssembly API Reference v1.8.1¶

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

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

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

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

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

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

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

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

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

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>

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

Returns: boolean

languageCount()¶

Return the number of available languages.

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

Signature:

function languageCount(): 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

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

Returns: void 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

Returns: void 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

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

manifestLanguages()¶

Return all language names available in the remote manifest (305).

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>

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>

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

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

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.

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

withCacheDir()¶

Create a download manager with a custom cache directory.

Signature:

static withCacheDir(version: string, cacheDir: string): DownloadManager

installedLanguages()¶

List languages that are already downloaded and cached.

Signature:

installedLanguages(): Array<string>

downloadAllBestEffort()¶

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

Unlike 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

cleanCache()¶

Remove all cached parser libraries.

Signature:

cleanCache(): void

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¶

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

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>

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

languageCount()¶

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

Signature:

languageCount(): number

process()¶

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

Signature:

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

default()¶

Signature:

static default(): 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

kind()¶

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

Signature:

kind(): string

startByte()¶

Return the inclusive start byte offset of this node.

Signature:

startByte(): number

endByte()¶

Return the exclusive end byte offset of this node.

Signature:

endByte(): 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

startPosition()¶

Return the start Point (row, column).

Signature:

startPosition(): Point

endPosition()¶

Return the end Point (row, column).

Signature:

endPosition(): Point

isNamed()¶

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

Signature:

isNamed(): boolean

isError()¶

True when this is an error node.

Signature:

isError(): boolean

isMissing()¶

True when this is a missing-token node.

Signature:

isMissing(): boolean

isExtra()¶

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

Signature:

isExtra(): boolean

hasError()¶

True when this node or any descendant is an error.

Signature:

hasError(): boolean

parent()¶

Return this node's parent, if any.

Signature:

parent(): Node | null

child()¶

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

Signature:

child(index: number): Node | null

childCount()¶

Total number of children (including unnamed).

Signature:

childCount(): number

namedChild()¶

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

Signature:

namedChild(index: number): Node | null

namedChildCount()¶

Number of named children of this node.

Signature:

namedChildCount(): number

childByFieldName()¶

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

Signature:

childByFieldName(name: string): Node | null

toSexp()¶

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

Signature:

toSexp(): string

walk()¶

Return a TreeCursor positioned at this node.

Signature:

walk(): 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¶

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

parse()¶

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

Signature:

parse(source: string): 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

reset()¶

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

Signature:

reset(): void

default()¶

Signature:

static default(): Parser

Point¶

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

Methods¶

from()¶

Signature:

static from(p: Point): Point

ProcessConfig¶

Configuration for the process() function.

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

Methods¶

default()¶

Signature:

static default(): ProcessConfig

withChunking()¶

Enable chunking with the given maximum chunk size in bytes.

Signature:

withChunking(maxSize: number): ProcessConfig

all()¶

Enable all analysis features.

Signature:

all(): ProcessConfig

minimal()¶

Disable all analysis features (only metrics computed).

Signature:

minimal(): 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

walk()¶

Return a TreeCursor positioned at the root.

Signature:

walk(): TreeCursor

TreeCursor¶

A cursor for traversing a Tree.

Methods¶

node()¶

Return the Node at the cursor's current position.

Signature:

node(): Node

gotoFirstChild()¶

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

Signature:

gotoFirstChild(): boolean

gotoParent()¶

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

Signature:

gotoParent(): boolean

gotoNextSibling()¶

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

Signature:

gotoNextSibling(): boolean

fieldName()¶

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

Signature:

fieldName(): string | null

Enums¶

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.

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).

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.

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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