Interface Extract

crates/csskit/src/commands/extract.rs:102–256

Trait for a command that walks a CSS AST and emits records. Implementors define: - `Row`: the command-specific data payload - `extract()`: walk one parsed stylesheet and collect (span, row) pairs - `render_text()`: format one row for text output The framework (`run()`) handles: - Looping over input files - Parsing each to a StyleSheet - Calling `extract()` and dispatching to text or JSON output

/// - Per-file envelopes in JSON mode (always emitted, even for empty results)
/// - Error handling and file headers (text mode)
pub trait Extract: Sized {
	/// The command-specific payload type.
	type Row: Serialize;

	/// Per-file context computed after parsing, before rendering.
	type FileContext: Default;

	/// Return reference to input args.
	fn input(&self) -> &InputArgs;

	/// Return the chosen output format.
	fn format(&self) -> OutputFormat;

	/// Walk the stylesheet and emit (span, row) pairs into `out`.
	fn extract<'a>(&self, stylesheet: &StyleSheet<'a>, src: &str, out: &mut Vec<(Span, Self::Row)>);

	/// Format one row for text output.
	fn render_text(&self, ctx: &Self::FileContext, file: &str, src: &str, span: Span, row: &Self::Row, color: bool);

	/// Build the per-file context from the parsed stylesheet and source.
	fn build_context<'a>(&self, _stylesheet: &StyleSheet<'a>, _src: &str) -> Self::FileContext {
		Self::FileContext::default()
	}

	/// Whether to print a filename header before each file's rows in text mode.
	fn show_file_header(&self) -> bool {
		true
	}

	/// Called in text mode just before a file's rows are rendered, after the file header.
	fn render_file_preamble(&self, _file: &str, _row_count: usize, _color: bool) {}

	/// Called in text mode when a file yields no rows.
	fn on_no_results(&self, _file: &str) {}

	/// Try parsing source as raw content before falling back to StyleSheet.
	/// Return true if handled.
	fn try_content(&self, _src: &str, _bump: &Bump, _out: &mut Vec<(Span, Self::Row)>) -> bool {
		false
	}

	/// Parse and extract from one file. Returns Ok(rows) or Err(error_record).
	/// `on_stylesheet` is called with the stylesheet while still in scope.
	fn parse_and_extract_file(
		&self,
		file: &str,
		src: &str,
		bump: &Bump,
		on_stylesheet: &mut dyn for<'a> FnMut(&StyleSheet<'a>),
	) -> Result<Vec<(Span, Self::Row)>, ErrorRecord> {
		let mut rows = Vec::new();
		if self.try_content(src, bump, &mut rows) {
			return Ok(rows);
		}

		let lexer = Lexer::new(&CssAtomSet::ATOMS, src);
		let mut parser = Parser::new(bump, src, lexer);
		let result = parser.parse_entirely::<StyleSheet>();