dedupe token restoring

src/index.ts

@@ -13,6 +13,7 @@ export { type ParserOptions } from './parse'
 
 // Types
 export { CSSNode, type CSSNodeType } from './css-node'
+export type { LexerPosition } from './lexer'
 
 export {
 	ATTR_OPERATOR_NONE,

src/lexer.ts

@@ -57,6 +57,17 @@ const CHAR_UPPERCASE_E = 0x45 // E
 const CHAR_CARRIAGE_RETURN = 0x0d // \r
 const CHAR_LINE_FEED = 0x0a // \n
 
+export interface LexerPosition {
+	pos: number
+	line: number
+	column: number
+	token_type: TokenType
+	token_start: number
+	token_end: number
+	token_line: number
+	token_column: number
+}
+
 export class Lexer {
 	source: string
 	pos: number
@@ -542,4 +553,36 @@ export class Lexer {
 			column: this.token_column,
 		}
 	}
+
+	/**
+	 * Save complete lexer state for backtracking
+	 * @returns Object containing all lexer state
+	 */
+	save_position(): LexerPosition {
+		return {
+			pos: this.pos,
+			line: this.line,
+			column: this.column,
+			token_type: this.token_type,
+			token_start: this.token_start,
+			token_end: this.token_end,
+			token_line: this.token_line,
+			token_column: this.token_column,
+		}
+	}
+
+	/**
+	 * Restore lexer state from saved position
+	 * @param saved The saved position to restore
+	 */
+	restore_position(saved: LexerPosition): void {
+		this.pos = saved.pos
+		this.line = saved.line
+		this.column = saved.column
+		this.token_type = saved.token_type
+		this.token_start = saved.token_start
+		this.token_end = saved.token_end
+		this.token_line = saved.token_line
+		this.token_column = saved.token_column
+	}
 }

src/parse-anplusb.ts

@@ -136,7 +136,7 @@ export class ANplusBParser {
 		// Handle +n pattern
 		if (this.lexer.token_type === TOKEN_DELIM && this.source.charCodeAt(this.lexer.token_start) === CHAR_PLUS) {
 			// Look ahead for 'n'
-			const saved_pos = this.lexer.pos
+			const saved = this.lexer.save_position()
 			this.lexer.next_token_fast(true)
 
 			if ((this.lexer.token_type as TokenType) === TOKEN_IDENT) {
@@ -146,7 +146,7 @@ export class ANplusBParser {
 				if (first_char === 0x6e /* n */) {
 					// Store +n as authored (including the +)
 					a = '+n'
-					a_start = saved_pos - 1 // Position of the + delim
+					a_start = saved.pos - 1 // Position of the + delim
 					a_end = this.lexer.token_start + 1
 
 					// Check for attached n-digit pattern
@@ -171,7 +171,7 @@ export class ANplusBParser {
 				}
 			}
 
-			this.lexer.pos = saved_pos
+			this.lexer.restore_position(saved)
 		}
 
 		// Handle dimension tokens: 2n, 3n+1, -5n-2

src/parse-atrule-prelude.ts

@@ -506,9 +506,7 @@ export class AtRulePreludeParser {
 	// Parse import layer: layer or layer(name)
 	private parse_import_layer(): number | null {
 		// Peek at next token
-		let saved_pos = this.lexer.pos
-		let saved_line = this.lexer.line
-		let saved_column = this.lexer.column
+		const saved = this.lexer.save_position()
 
 		this.next_token()
 
@@ -569,18 +567,14 @@ export class AtRulePreludeParser {
 		}
 
 		// Not a layer, restore position
-		this.lexer.pos = saved_pos
-		this.lexer.line = saved_line
-		this.lexer.column = saved_column
+		this.lexer.restore_position(saved)
 		return null
 	}
 
 	// Parse import supports: supports(condition)
 	private parse_import_supports(): number | null {
 		// Peek at next token
-		let saved_pos = this.lexer.pos
-		let saved_line = this.lexer.line
-		let saved_column = this.lexer.column
+		const saved = this.lexer.save_position()
 
 		this.next_token()
 
@@ -621,9 +615,7 @@ export class AtRulePreludeParser {
 		}
 
 		// Not supports(), restore position
-		this.lexer.pos = saved_pos
-		this.lexer.line = saved_line
-		this.lexer.column = saved_column
+		this.lexer.restore_position(saved)
 		return null
 	}
 
@@ -634,16 +626,12 @@ export class AtRulePreludeParser {
 
 	// Helper: Peek at next token type without consuming
 	private peek_token_type(): number {
-		let saved_pos = this.lexer.pos
-		let saved_line = this.lexer.line
-		let saved_column = this.lexer.column
+		const saved = this.lexer.save_position()
 
 		this.next_token()
 		let type = this.lexer.token_type
 
-		this.lexer.pos = saved_pos
-		this.lexer.line = saved_line
-		this.lexer.column = saved_column
+		this.lexer.restore_position(saved)
 
 		return type
 	}

src/parse-selector.ts

@@ -174,9 +174,7 @@ export class SelectorParser {
 
 		// Check for leading combinator (relative selector) if allowed
 		if (allow_relative && this.lexer.pos < this.selector_end) {
-			let saved_pos = this.lexer.pos
-			let saved_line = this.lexer.line
-			let saved_column = this.lexer.column
+			const saved = this.lexer.save_position()
 
 			this.lexer.next_token_fast(false)
 			let token_type = this.lexer.token_type
@@ -192,15 +190,11 @@ export class SelectorParser {
 					// Continue to parse the rest normally
 				} else {
 					// Not a combinator, restore position
-					this.lexer.pos = saved_pos
-					this.lexer.line = saved_line
-					this.lexer.column = saved_column
+					this.lexer.restore_position(saved)
 				}
 			} else {
 				// Not a delimiter, restore position
-				this.lexer.pos = saved_pos
-				this.lexer.line = saved_line
-				this.lexer.column = saved_column
+				this.lexer.restore_position(saved)
 			}
 		}
 
@@ -225,25 +219,19 @@ export class SelectorParser {
 			}
 
 			// Peek ahead for comma or end
-			let saved_pos = this.lexer.pos
-			let saved_line = this.lexer.line
-			let saved_column = this.lexer.column
+			const saved = this.lexer.save_position()
 			this.skip_whitespace()
 			if (this.lexer.pos >= this.selector_end) break
 
 			this.lexer.next_token_fast(false)
 			let token_type = this.lexer.token_type
 			if (token_type === TOKEN_COMMA || this.lexer.pos >= this.selector_end) {
 				// Reset position for comma handling
-				this.lexer.pos = saved_pos
-				this.lexer.line = saved_line
-				this.lexer.column = saved_column
+				this.lexer.restore_position(saved)
 				break
 			}
 			// Reset for next iteration
-			this.lexer.pos = saved_pos
-			this.lexer.line = saved_line
-			this.lexer.column = saved_column
+			this.lexer.restore_position(saved)
 			break
 		}
 
@@ -271,9 +259,7 @@ export class SelectorParser {
 
 		while (this.lexer.pos < this.selector_end) {
 			// Save lexer state before getting token
-			let saved_pos = this.lexer.pos
-			let saved_line = this.lexer.line
-			let saved_column = this.lexer.column
+			const saved = this.lexer.save_position()
 			this.lexer.next_token_fast(false)
 
 			if (this.lexer.token_start >= this.selector_end) break
@@ -286,9 +272,7 @@ export class SelectorParser {
 				parts.push(part)
 			} else {
 				// Not a simple selector part, restore lexer state and break
-				this.lexer.pos = saved_pos
-				this.lexer.line = saved_line
-				this.lexer.column = saved_column
+				this.lexer.restore_position(saved)
 				break
 			}
 		}
@@ -409,17 +393,13 @@ export class SelectorParser {
 	// Parse class selector (.classname)
 	private parse_class_selector(dot_pos: number): number | null {
 		// Save lexer state for potential restoration
-		let saved_pos = this.lexer.pos
-		let saved_line = this.lexer.line
-		let saved_column = this.lexer.column
+		const saved = this.lexer.save_position()
 
 		// Next token should be identifier
 		this.lexer.next_token_fast(false)
 		if (this.lexer.token_type !== TOKEN_IDENT) {
 			// Restore lexer state and return null
-			this.lexer.pos = saved_pos
-			this.lexer.line = saved_line
-			this.lexer.column = saved_column
+			this.lexer.restore_position(saved)
 			return null
 		}
 
@@ -607,9 +587,7 @@ export class SelectorParser {
 	// Parse pseudo-class or pseudo-element (:hover, ::before)
 	private parse_pseudo(start: number): number | null {
 		// Save lexer state for potential restoration
-		let saved_pos = this.lexer.pos
-		let saved_line = this.lexer.line
-		let saved_column = this.lexer.column
+		const saved = this.lexer.save_position()
 
 		// Check for double colon (::)
 		let is_pseudo_element = false
@@ -643,9 +621,7 @@ export class SelectorParser {
 		}
 
 		// Restore lexer state and return null
-		this.lexer.pos = saved_pos
-		this.lexer.line = saved_line
-		this.lexer.column = saved_column
+		this.lexer.restore_position(saved)
 		return null
 	}
 
@@ -716,9 +692,7 @@ export class SelectorParser {
 				// Parse as selector (for :is(), :where(), :has(), etc.)
 				// Save current lexer state and selector_end
 				let saved_selector_end = this.selector_end
-				let saved_pos = this.lexer.pos
-				let saved_line = this.lexer.line
-				let saved_column = this.lexer.column
+				const saved = this.lexer.save_position()
 
 				// Recursively parse the content as a selector
 				// Only :has() accepts relative selectors (starting with combinator)
@@ -727,9 +701,7 @@ export class SelectorParser {
 
 				// Restore lexer state and selector_end
 				this.selector_end = saved_selector_end
-				this.lexer.pos = saved_pos
-				this.lexer.line = saved_line
-				this.lexer.column = saved_column
+				this.lexer.restore_position(saved)
 
 				// Add as child if parsed successfully
 				if (child_selector !== null) {
@@ -759,9 +731,7 @@ export class SelectorParser {
 	private parse_lang_identifiers(start: number, end: number, parent_node: number): void {
 		// Save current lexer state
 		let saved_selector_end = this.selector_end
-		let saved_pos = this.lexer.pos
-		let saved_line = this.lexer.line
-		let saved_column = this.lexer.column
+		const saved = this.lexer.save_position()
 
 		// Set lexer to parse this range
 		this.lexer.pos = start
@@ -822,9 +792,7 @@ export class SelectorParser {
 
 		// Restore lexer state
 		this.selector_end = saved_selector_end
-		this.lexer.pos = saved_pos
-		this.lexer.line = saved_line
-		this.lexer.column = saved_column
+		this.lexer.restore_position(saved)
 	}
 
 	// Parse An+B expression for nth-* pseudo-classes
@@ -846,9 +814,7 @@ export class SelectorParser {
 
 			// Save current state
 			let saved_selector_end = this.selector_end
-			let saved_pos = this.lexer.pos
-			let saved_line = this.lexer.line
-			let saved_column = this.lexer.column
+			const saved = this.lexer.save_position()
 
 			// Parse selector list
 			this.selector_end = end
@@ -857,9 +823,7 @@ export class SelectorParser {
 
 			// Restore state
 			this.selector_end = saved_selector_end
-			this.lexer.pos = saved_pos
-			this.lexer.line = saved_line
-			this.lexer.column = saved_column
+			this.lexer.restore_position(saved)
 
 			// Create NTH_OF wrapper
 			let of_node = this.arena.create_node()

src/parse.ts

@@ -283,28 +283,14 @@ export class Parser {
 		let decl_column = this.lexer.token_column
 
 		// Lookahead: save lexer state before consuming
-		let saved_pos = this.lexer.pos
-		let saved_line = this.lexer.line
-		let saved_column = this.lexer.column
-		let saved_token_type = this.lexer.token_type
-		let saved_token_start = this.lexer.token_start
-		let saved_token_end = this.lexer.token_end
-		let saved_token_line = this.lexer.token_line
-		let saved_token_column = this.lexer.token_column
+		const saved = this.lexer.save_position()
 
 		this.next_token() // consume property name
 
 		// Expect ':'
 		if (this.peek_type() !== TOKEN_COLON) {
 			// Restore lexer state and return null
-			this.lexer.pos = saved_pos
-			this.lexer.line = saved_line
-			this.lexer.column = saved_column
-			this.lexer.token_type = saved_token_type
-			this.lexer.token_start = saved_token_start
-			this.lexer.token_end = saved_token_end
-			this.lexer.token_line = saved_token_line
-			this.lexer.token_column = saved_token_column
+			this.lexer.restore_position(saved)
 			return null
 		}
 		this.next_token() // consume ':'
@@ -340,14 +326,7 @@ export class Parser {
 			// If we encounter '{', this is actually a style rule, not a declaration
 			if (token_type === TOKEN_LEFT_BRACE) {
 				// Restore lexer state and return null
-				this.lexer.pos = saved_pos
-				this.lexer.line = saved_line
-				this.lexer.column = saved_column
-				this.lexer.token_type = saved_token_type
-				this.lexer.token_start = saved_token_start
-				this.lexer.token_end = saved_token_end
-				this.lexer.token_line = saved_token_line
-				this.lexer.token_column = saved_token_column
+				this.lexer.restore_position(saved)
 				return null
 			}