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// Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
/// Contains a code printer that generates code by recording the source maps.
library source_maps.printer;
import 'package:source_span/source_span.dart';
import 'builder.dart';
import 'src/source_map_span.dart';
const int _LF = 10;
const int _CR = 13;
/// A simple printer that keeps track of offset locations and records source
/// maps locations.
class Printer {
final String filename;
final StringBuffer _buff = new StringBuffer();
final SourceMapBuilder _maps = new SourceMapBuilder();
String get text => _buff.toString();
String get map => _maps.toJson(filename);
/// Current source location mapping.
SourceLocation _loc;
/// Current line in the buffer;
int _line = 0;
/// Current column in the buffer.
int _column = 0;
/// Add [str] contents to the output, tracking new lines to track correct
/// positions for span locations. When [projectMarks] is true, this method
/// adds a source map location on each new line, projecting that every new
/// line in the target file (printed here) corresponds to a new line in the
/// source file.
void add(String str, {projectMarks: false}) {
var chars = str.runes.toList();
var length = chars.length;
for (int i = 0; i < length; i++) {
var c = chars[i];
if (c == _LF || (c == _CR && (i + 1 == length || chars[i + 1] != _LF))) {
// Return not followed by line-feed is treated as a new line.
_column = 0;
if (projectMarks && _loc != null) {
if (_loc is FileLocation) {
var file = (_loc as FileLocation).file;
mark(file.location(file.getOffset(_loc.line + 1)));
} else {
mark(new SourceLocation(0,
sourceUrl: _loc.sourceUrl, line: _loc.line + 1, column: 0));
} else {
/// Append a [total] number of spaces in the target file. Typically used for
/// formatting indentation.
void addSpaces(int total) {
for (int i = 0; i < total; i++) _buff.write(' ');
_column += total;
/// Marks that the current point in the target file corresponds to the [mark]
/// in the source file, which can be either a [SourceLocation] or a
/// [SourceSpan]. When the mark is a [SourceMapSpan] with `isIdentifier` set,
/// this also records the name of the identifier in the source map
/// information.
void mark(mark) {
var loc;
var identifier = null;
if (mark is SourceLocation) {
loc = mark;
} else if (mark is SourceSpan) {
loc = mark.start;
if (mark is SourceMapSpan && mark.isIdentifier) identifier = mark.text;
new SourceLocation(_buff.length, line: _line, column: _column),
_loc = loc;
/// A more advanced printer that keeps track of offset locations to record
/// source maps, but additionally allows nesting of different kind of items,
/// including [NestedPrinter]s, and it let's you automatically indent text.
/// This class is especially useful when doing code generation, where different
/// peices of the code are generated independently on separate printers, and are
/// finally put together in the end.
class NestedPrinter implements NestedItem {
/// Items recoded by this printer, which can be [String] literals,
/// [NestedItem]s, and source map information like [SourceLocation] and
/// [SourceSpan].
List _items = [];
/// Internal buffer to merge consecutive strings added to this printer.
StringBuffer _buff;
/// Current indentation, which can be updated from outside this class.
int indent;
/// Item used to indicate that the following item is copied from the original
/// source code, and hence we should preserve source-maps on every new line.
static final _ORIGINAL = new Object();
NestedPrinter([this.indent = 0]);
/// Adds [object] to this printer. [object] can be a [String],
/// [NestedPrinter], or anything implementing [NestedItem]. If [object] is a
/// [String], the value is appended directly, without doing any formatting
/// changes. If you wish to add a line of code with automatic indentation, use
/// [addLine] instead. [NestedPrinter]s and [NestedItem]s are not processed
/// until [build] gets called later on. We ensure that [build] emits every
/// object in the order that they were added to this printer.
/// The [location] and [span] parameters indicate the corresponding source map
/// location of [object] in the original input. Only one, [location] or
/// [span], should be provided at a time.
/// Indicate [isOriginal] when [object] is copied directly from the user code.
/// Setting [isOriginal] will make this printer propagate source map locations
/// on every line-break.
void add(object,
{SourceLocation location, SourceSpan span, bool isOriginal: false}) {
if (object is! String || location != null || span != null || isOriginal) {
assert(location == null || span == null);
if (location != null) _items.add(location);
if (span != null) _items.add(span);
if (isOriginal) _items.add(_ORIGINAL);
if (object is String) {
} else {
/// Append `2 * indent` spaces to this printer.
void insertIndent() => _indent(indent);
/// Add a [line], autoindenting to the current value of [indent]. Note,
/// indentation is not inferred from the contents added to this printer. If a
/// line starts or ends an indentation block, you need to also update [indent]
/// accordingly. Also, indentation is not adapted for nested printers. If
/// you add a [NestedPrinter] to this printer, its indentation is set
/// separately and will not include any the indentation set here.
/// The [location] and [span] parameters indicate the corresponding source map
/// location of [object] in the original input. Only one, [location] or
/// [span], should be provided at a time.
void addLine(String line, {SourceLocation location, SourceSpan span}) {
if (location != null || span != null) {
assert(location == null || span == null);
if (location != null) _items.add(location);
if (span != null) _items.add(span);
if (line == null) return;
if (line != '') {
// We don't indent empty lines.
/// Appends a string merging it with any previous strings, if possible.
void _appendString(String s) {
if (_buff == null) _buff = new StringBuffer();
/// Adds all of the current [_buff] contents as a string item.
void _flush() {
if (_buff != null) {
_buff = null;
void _indent(int indent) {
for (int i = 0; i < indent; i++) _appendString(' ');
/// Returns a string representation of all the contents appended to this
/// printer, including source map location tokens.
String toString() {
return (new StringBuffer()..writeAll(_items)).toString();
/// [Printer] used during the last call to [build], if any.
Printer printer;
/// Returns the text produced after calling [build].
String get text => printer.text;
/// Returns the source-map information produced after calling [build].
String get map =>;
/// Builds the output of this printer and source map information. After
/// calling this function, you can use [text] and [map] to retrieve the
/// geenrated code and source map information, respectively.
void build(String filename) {
writeTo(printer = new Printer(filename));
/// Implements the [NestedItem] interface.
void writeTo(Printer printer) {
bool propagate = false;
for (var item in _items) {
if (item is NestedItem) {
} else if (item is String) {
printer.add(item, projectMarks: propagate);
propagate = false;
} else if (item is SourceLocation || item is SourceSpan) {
} else if (item == _ORIGINAL) {
// we insert booleans when we are about to quote text that was copied
// from the original source. In such case, we will propagate marks on
// every new-line.
propagate = true;
} else {
throw new UnsupportedError('Unknown item type: $item');
/// An item added to a [NestedPrinter].
abstract class NestedItem {
/// Write the contents of this item into [printer].
void writeTo(Printer printer);