Add integrity checking to tests and fix various bugs

.eslintrc

@@ -6,6 +6,7 @@
         "keyword-spacing": [ 2, { "before": true, "after": true } ],
         "space-before-blocks": [ 2, "always" ],
         "space-before-function-paren": [ 2, "always" ],
+        "space-in-parens": [ 2, "always" ],
         "no-mixed-spaces-and-tabs": [ 2, "smart-tabs" ],
         "object-shorthand":  [2, "always" ],
         "no-const-assign": 2,

src/MagicString.js

@@ -235,13 +235,9 @@ MagicString.prototype = {
 							if ( charIndex === chunk.start ) {
 								chunk.prependRight( indentStr );
 							} else {
-								const rhs = chunk.split( charIndex );
-								rhs.prependRight( indentStr );
-
-								this.byStart[ charIndex ] = rhs;
-								this.byEnd[ charIndex ] = chunk;
-
-								chunk = rhs;
+								this._splitChunk( chunk, charIndex );
+								chunk = chunk.next;
+								chunk.prependRight( indentStr );
 							}
 						}
 					}
@@ -313,7 +309,7 @@ MagicString.prototype = {
 		}
 
 		first.previous = newLeft;
-		last.next = newRight;
+		last.next = newRight || null;
 
 		if ( !newLeft ) this.firstChunk = first;
 		if ( !newRight ) this.lastChunk = last;
@@ -362,15 +358,15 @@ MagicString.prototype = {
 
 			first.edit( content, storeName, contentOnly );
 
-			if ( last ) {
-				first.next = last.next;
-			} else {
-				first.next = null;
-				this.lastChunk = first;
-			}
+			if ( first !== last ) {
+				let chunk = first.next;
+				while ( chunk !== last ) {
+					chunk.edit( '', false );
+					chunk = chunk.next;
+				}
 
-			first.original = this.original.slice( start, end );
-			first.end = end;
+				chunk.edit( '', false );
+			}
 		}
 
 		else {
@@ -586,10 +582,13 @@ MagicString.prototype = {
 
 			// if chunk was trimmed, we have a new lastChunk
 			if ( chunk.end !== end ) {
-				this.lastChunk = chunk.next;
+				if ( this.lastChunk === chunk ) {
+					this.lastChunk = chunk.next;
+				}
 
 				this.byEnd[ chunk.end ] = chunk;
 				this.byStart[ chunk.next.start ] = chunk.next;
+				this.byEnd[ chunk.next.end ] = chunk.next;
 			}
 
 			if ( aborted ) return this;
@@ -617,6 +616,7 @@ MagicString.prototype = {
 
 				this.byEnd[ chunk.end ] = chunk;
 				this.byStart[ chunk.next.start ] = chunk.next;
+				this.byEnd[ chunk.next.end ] = chunk.next;
 			}
 
 			if ( aborted ) return this;

test/MagicString.js

@@ -1,6 +1,6 @@
 const assert = require( 'assert' );
 const SourceMapConsumer = require( 'source-map' ).SourceMapConsumer;
-const MagicString = require( '../' );
+const MagicString = require( './utils/IntegrityCheckingMagicString' );
 
 require( 'source-map-support' ).install();
 require( 'console-group' ).install();
@@ -808,6 +808,15 @@ describe( 'MagicString', () => {
 			s.move( 6, 9, 3 );
 			assert.throws( () => s.overwrite( 5, 7, 'XX' ), /Cannot overwrite across a split point/ );
 		});
+
+		it ( 'allows later insertions at the end', () => {
+			const s = new MagicString( 'abcdefg' );
+
+			s.appendLeft(4, '(');
+			s.overwrite( 2, 7, '' );
+			s.appendLeft(7, 'h');
+			assert.equal( s.toString(), 'abh' );
+		});
 	});
 
 	describe( 'prepend', () => {

test/utils/IntegrityCheckingMagicString.js

@@ -0,0 +1,46 @@
+const MagicString = require( '../../' );
+const assert = require( 'assert' );
+
+class IntegrityCheckingMagicString extends MagicString {
+	checkIntegrity () {
+		let prevChunk = null;
+		let chunk = this.firstChunk;
+		let numNodes = 0;
+		while ( chunk ) {
+			assert.strictEqual( this.byStart[chunk.start], chunk );
+			assert.strictEqual( this.byEnd[chunk.end], chunk );
+			assert.strictEqual( chunk.previous, prevChunk );
+			if ( prevChunk ) {
+				assert.strictEqual( prevChunk.next, chunk );
+			}
+			prevChunk = chunk;
+			chunk = chunk.next;
+			numNodes++;
+		}
+		assert.strictEqual( prevChunk, this.lastChunk );
+		assert.strictEqual( this.lastChunk.next, null );
+		assert.strictEqual( Object.keys(this.byStart).length, numNodes );
+		assert.strictEqual( Object.keys(this.byEnd).length, numNodes );
+	}
+}
+
+for (const key in MagicString.prototype) {
+	if ( !MagicString.prototype.hasOwnProperty( key ) ) {
+		continue;
+	}
+	const func = MagicString.prototype[key];
+	if ( typeof func === 'function' ) {
+		IntegrityCheckingMagicString.prototype[key] = function () {
+			const result = func.apply( this, arguments );
+			try {
+				this.checkIntegrity();
+			} catch ( e ) {
+				e.message = `Integrity error after invoking ${key}:\n${e.message}`;
+				throw e;
+			}
+			return result;
+		};
+	}
+}
+
+module.exports = IntegrityCheckingMagicString;