From 52f47407bab81f7cd8c7a6b11f39376bc935073f Mon Sep 17 00:00:00 2001
From: Rich-Harris <richard.a.harris@gmail.com>
Date: Sun, 10 Apr 2016 23:47:33 -0400
Subject: [PATCH] split unedited chunks when trimming, to ensure correct
 sourcemaps (#53)

---
 src/MagicString.js | 37 +++++++++++++++++++++----------------
 test/index.js      | 28 ++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+), 16 deletions(-)

diff --git a/src/MagicString.js b/src/MagicString.js
index c9913b9..d12f6b0 100644
--- a/src/MagicString.js
+++ b/src/MagicString.js
@@ -354,18 +354,19 @@ MagicString.prototype = {
 
 		do {
 			let lastChunk = this.chunks[ this.chunks.length - 1 ];
-			if ( rx.test( lastChunk.content ) ) {
-				lastChunk.edit( lastChunk.content.replace( rx, '' ) );
-			}
 
-			if ( lastChunk.content.length || this.chunks.length === 1 ) {
-				break;
+			const match = rx.exec( lastChunk.content );
+			if ( !match ) return this;
+
+			if ( lastChunk.edited ) {
+				lastChunk.edit( lastChunk.content.slice( 0, match.index ) );
 			} else {
-				this.chunks.pop();
+				lastChunk.split( match.index + lastChunk.start ); // generated chunk is discarded
 			}
-		} while ( true );
 
-		return this;
+			if ( match.index > 0 || this.chunks.length === 1 ) return this;
+			this.chunks.pop();
+		} while ( true );
 	},
 
 	trimStart ( charType ) {
@@ -376,17 +377,21 @@ MagicString.prototype = {
 
 		do {
 			let firstChunk = this.chunks[0];
-			if ( rx.test( firstChunk.content ) ) {
-				firstChunk.edit( firstChunk.content.replace( rx, '' ) );
-			}
 
-			if ( firstChunk.content.length || this.chunks.length === 1 ) {
-				break;
+			const match = rx.exec( firstChunk.content );
+			if ( !match ) return this;
+
+			const end = match.index + match[0].length;
+
+			if ( firstChunk.edited ) {
+				firstChunk.edit( firstChunk.content.slice( match.index ) );
 			} else {
-				this.chunks.shift();
+				const newChunk = firstChunk.split( end + firstChunk.start ); // existing chunk is discarded
+				this.chunks[0] = newChunk;
 			}
-		} while ( true );
 
-		return this;
+			if ( end < firstChunk.content.length || this.chunks.length === 1 ) return this;
+			this.chunks.shift();
+		} while ( true );
 	}
 };
diff --git a/test/index.js b/test/index.js
index 945dcd8..4161383 100644
--- a/test/index.js
+++ b/test/index.js
@@ -260,6 +260,34 @@ describe( 'MagicString', function () {
 				assert.equal( loc.column, i );
 			});
 		});
+
+		it.only( 'generates a map with trimmed content (#53)', function () {
+			var s = new MagicString( 'abcdefghijkl ' ).trim();
+			var map = s.generateMap({
+				file: 'output',
+				source: 'input',
+				includeContent: true,
+				hires: true
+			});
+
+			var smc = new SourceMapConsumer( map );
+			var loc = smc.originalPositionFor({ line: 1, column: 11 });
+
+			assert.equal( loc.column, 11 );
+
+			s = new MagicString( ' abcdefghijkl' ).trim();
+			map = s.generateMap({
+				file: 'output',
+				source: 'input',
+				includeContent: true,
+				hires: true
+			});
+
+			smc = new SourceMapConsumer( map );
+			loc = smc.originalPositionFor({ line: 1, column: 1 });
+
+			assert.equal( loc.column, 2 );
+		});
 	});
 
 	describe( 'getIndentString', function () {