Syntax Text Handling

Syntax Text Handling

Use typed syntax APIs and preserve source ownership instead of converting syntax text into strings.

Inspect Before Implementing

Do not infer an AST shape from source spelling. Inspect the parser quick test for the language and search generated node definitions and existing consumers. Load testing-codegen for the current quick-test command.

Check every relevant union member and framework-specific value representation. Similar source syntax may use different typed nodes.

Text Accessors

SyntaxNode::text_trimmed() removes only outer trivia. Whitespace and comments between child tokens remain, so it is not a semantic accessor for a multi-token node. Prefer a typed token, typed accessor, or structural match.

Do not call .to_string(), .to_trimmed_string(), or format! merely to compare syntax text. Borrow a &str or retain a TokenText.

Quoted Strings

Use the syntax crate's inner_string_text() implementation. It handles the language's token representation and returns token-backed text.

let string = value.as_html_string()?;
let inner = string.inner_string_text().ok()?;
let matches_handler = inner.text() == "handler";

Do not strip quotes with byte slicing. Besides allocating or risking invalid boundaries, manual slicing duplicates language-specific behavior already covered by the accessor and its tests.

Store Substrings Without Allocation

TokenText already stores a green token plus a token-relative TextRange. Use its existing APIs instead of adding another token-and-range wrapper:

let word = inner.clone().slice(word_range);
let text = word.text();
let relative_range = word.relative_range();
let source_range = word.source_range(value_token.text_range());

Pass slice() a range relative to the current TokenText; it retains the underlying token and adjusts the selected range. relative_range() returns the resulting range relative to the whole token, while source_range() translates it using the whole token's file range. Build slice ranges from valid byte boundaries in the current text.

Embedded Languages

Verify value shapes per framework and syntax version. For example, an HTML-family attribute may hold a quoted HtmlString, a single text expression, or a framework-specific directive node. Do not handle one shape and assume the others share its accessor or offset rules.

Keep embedded-language parsing concerns separate:

• parser nodes establish the source shape;
• syntax helpers extract source-backed text;
• embedding code translates source ranges and selects the embedding kind;
• analyzers consume the resulting typed data.

Support legacy syntax only when the task requires it and the current parser represents it.

Temporary Borrows

Typed accessors often return owned wrapper nodes whose tokens borrow through that wrapper. Bind intermediate values when a chained expression would drop the owner too early:

let value_node = attribute.value().ok()?;
let string = value_node.as_html_string()?;
let token = string.value_token().ok()?;
let text = token.text_trimmed();

Do not solve a temporary-borrow error by converting to String unless the value genuinely must outlive its syntax tree.

Use Strongly Typed Nodes

Always prefer using specific, strongly typed syntax nodes (like AnyJsExpression, JsCallExpression) over generic, weakly typed syntax nodes (like JsSyntaxNode) in function parameters.

GOOD:

fn is_react_call(node: &JsCallExpression) -> bool { ... }

BAD:

fn is_react_call(node: &JsSyntaxNode) -> bool { ... }

You can use declare_node_union! to define custom sets of nodes.

Review Checklist

• The code uses a typed node or token rather than matching a multi-token node's rendered text.
• Token comparisons exclude trivia intentionally.
• Quote stripping uses the language helper.
• Stored text remains token-backed when the syntax tree outlives it.
• Relative ranges are relative to the stored token text, not the file.
• Absolute offsets account for quotes exactly once.
• Every relevant framework or union variant is covered or deliberately excluded.
• No allocation was introduced solely to satisfy borrowing or comparison.

References

• Token text: crates/biome_rowan/src/token_text.rs
• Syntax tokens: crates/biome_rowan/src/syntax/token.rs
• Syntax nodes: crates/biome_rowan/src/syntax/node.rs
• HTML string helpers: crates/biome_html_syntax/src/string_ext.rs
• Language-specific syntax extension modules under crates/biome_*_syntax/src/