dont throw on single-length sourcemap segment (#618)

src/utils/collapseSourcemaps.js

@@ -71,8 +71,7 @@ Link.prototype = { // TODO bring into line with others post-https://github.com/r
 
 			if ( segment[0] === column ) {
 				const source = this.sources[ segment[1] ];
-
+				if ( !source ) return null;
-				if ( !source ) throw new Error( 'Bad sourcemap' );
 
 				return source.traceSegment( segment[2], segment[3], this.names[ segment[4] ] || name );
 			}

test/sourcemaps/single-length-segments/_config.js

@@ -0,0 +1,37 @@
+var fs = require( 'fs' );
+var path = require( 'path' );
+var assert = require( 'assert' );
+var getLocation = require( '../../utils/getLocation' );
+var SourceMapConsumer = require( 'source-map' ).SourceMapConsumer;
+
+var original = fs.readFileSync( path.resolve( __dirname, 'main.js' ), 'utf-8' );
+
+module.exports = {
+	description: 'handles single-length sourcemap segments',
+	options: {
+		plugins: [
+			{
+				transform: function () {
+					return {
+						code: fs.readFileSync( path.resolve( __dirname, 'output.js' ), 'utf-8' ),
+						map: fs.readFileSync( path.resolve( __dirname, 'output.js.map' ), 'utf-8' )
+					};
+				}
+			}
+		],
+		moduleName: 'x'
+	},
+	test: function ( code, map ) {
+		var smc = new SourceMapConsumer( map );
+
+		[ 'Foo', 'log' ].forEach( function ( token ) {
+			var generatedLoc = getLocation( code, code.indexOf( token ) );
+			var originalLoc = smc.originalPositionFor( generatedLoc );
+			var expectedLoc = getLocation( original, original.indexOf( token ) );
+
+			assert.ok( /main/.test( originalLoc.source ) );
+			assert.equal( originalLoc.line, expectedLoc.line );
+			assert.equal( originalLoc.column, expectedLoc.column );
+		});
+	}
+};

test/sourcemaps/single-length-segments/main.js

@@ -0,0 +1,7 @@
+class Foo {
+	bar () {
+		console.log( 42 );
+	}
+}
+
+export { Foo };

test/sourcemaps/single-length-segments/output.js

@@ -0,0 +1,15 @@
+var Foo = function () {
+	function Foo() {
+		babelHelpers.classCallCheck(this, Foo);
+	}
+
+	babelHelpers.createClass(Foo, [{
+		key: "bar",
+		value: function bar() {
+			console.log(42);
+		}
+	}]);
+	return Foo;
+}();
+
+export { Foo };

test/sourcemaps/single-length-segments/output.js.map

@@ -0,0 +1,8 @@
+{
+	"version":3,
+	"sources":["index.js"],
+	"names":[],
+	"mappings":"IAAM,G;;;;;;;wBACE;AACN,WAAQ,GAAR,CAAa,EAAb;AACA;;;;;AAGF,SAAS,GAAT",
+	"file":"index.js",
+	"sourcesContent":["class Foo {\n\tbar () {\n\t\tconsole.log( 42 );\n\t}\n}\n\nexport { Foo };\n"]
+}