fix(compiler): make sourcemaps work in AOT mode

Inlcuded fixes:
- include preamble in generated source map
- always add a mapping for line/col 0 so that the
  generated sourcemap is not sparse
- use a uniue sourceUrl for inline templates even
  in the AOT case

packages/compiler/src/output/abstract_emitter.ts

@@ -18,7 +18,9 @@ export const CATCH_ERROR_VAR = o.variable('error');
 export const CATCH_STACK_VAR = o.variable('stack');
 
 export abstract class OutputEmitter {
-  abstract emitStatements(moduleUrl: string, stmts: o.Statement[], exportedVars: string[]): string;
+  abstract emitStatements(
+      srcFilePath: string, genFilePath: string, stmts: o.Statement[], exportedVars: string[],
+      preamble?: string): string;
 }
 
 class _EmittedLine {
@@ -89,13 +91,24 @@ export class EmitterVisitorContext {
         .join('\n');
   }
 
-  toSourceMapGenerator(file: string|null = null, startsAtLine: number = 0): SourceMapGenerator {
-    const map = new SourceMapGenerator(file);
+  toSourceMapGenerator(sourceFilePath: string, genFilePath: string, startsAtLine: number = 0):
+      SourceMapGenerator {
+    const map = new SourceMapGenerator(genFilePath);
+
+    let firstOffsetMapped = false;
+    const mapFirstOffsetIfNeeded = () => {
+      if (!firstOffsetMapped) {
+        map.addSource(sourceFilePath).addMapping(0, sourceFilePath, 0, 0);
+        firstOffsetMapped = true;
+      }
+    };
+
     for (let i = 0; i < startsAtLine; i++) {
       map.addLine();
+      mapFirstOffsetIfNeeded();
     }
 
-    this.sourceLines.forEach(line => {
+    this.sourceLines.forEach((line, lineIdx) => {
       map.addLine();
 
       const spans = line.srcSpans;
@@ -107,13 +120,17 @@ export class EmitterVisitorContext {
         col0 += parts[spanIdx].length;
         spanIdx++;
       }
+      if (spanIdx < spans.length && lineIdx === 0 && col0 === 0) {
+        firstOffsetMapped = true;
+      } else {
+        mapFirstOffsetIfNeeded();
+      }
 
       while (spanIdx < spans.length) {
         const span = spans[spanIdx];
         const source = span.start.file;
         const sourceLine = span.start.line;
         const sourceCol = span.start.col;
-
         map.addSource(source.url, source.content)
             .addMapping(col0, source.url, sourceLine, sourceCol);
 

packages/compiler/src/output/js_emitter.ts

@@ -18,29 +18,29 @@ import {ImportResolver} from './path_util';
 export class JavaScriptEmitter implements OutputEmitter {
   constructor(private _importResolver: ImportResolver) {}
 
-  emitStatements(genFilePath: string, stmts: o.Statement[], exportedVars: string[]): string {
+  emitStatements(
+      srcFilePath: string, genFilePath: string, stmts: o.Statement[], exportedVars: string[],
+      preamble: string = ''): string {
     const converter = new JsEmitterVisitor(genFilePath, this._importResolver);
     const ctx = EmitterVisitorContext.createRoot(exportedVars);
     converter.visitAllStatements(stmts, ctx);
 
-    const srcParts: string[] = [];
+    const preambleLines = preamble ? preamble.split('\n') : [];
     converter.importsWithPrefixes.forEach((prefix, importedFilePath) => {
       // Note: can't write the real word for import as it screws up system.js auto detection...
-      srcParts.push(
+      preambleLines.push(
           `var ${prefix} = req` +
           `uire('${this._importResolver.fileNameToModuleName(importedFilePath, genFilePath)}');`);
     });
 
-    srcParts.push(ctx.toSource());
-
-    const prefixLines = converter.importsWithPrefixes.size;
-    const sm = ctx.toSourceMapGenerator(genFilePath, prefixLines).toJsComment();
+    const sm =
+        ctx.toSourceMapGenerator(srcFilePath, genFilePath, preambleLines.length).toJsComment();
+    const lines = [...preambleLines, ctx.toSource(), sm];
     if (sm) {
-      srcParts.push(sm);
+      // always add a newline at the end, as some tools have bugs without it.
+      lines.push('');
     }
-    // always add a newline at the end, as some tools have bugs without it.
-    srcParts.push('');
-    return srcParts.join('\n');
+    return lines.join('\n');
   }
 }
 

packages/compiler/src/output/output_jit.ts

@@ -30,7 +30,7 @@ function evalExpression(
     // We don't want to hard code this fact, so we auto detect it via an empty function first.
     const emptyFn = new Function(...fnArgNames.concat('return null;')).toString();
     const headerLines = emptyFn.slice(0, emptyFn.indexOf('return null;')).split('\n').length - 1;
-    fnBody += `\n${ctx.toSourceMapGenerator(sourceUrl, headerLines).toJsComment()}`;
+    fnBody += `\n${ctx.toSourceMapGenerator(sourceUrl, sourceUrl, headerLines).toJsComment()}`;
   }
   return new Function(...fnArgNames.concat(fnBody))(...fnArgValues);
 }

packages/compiler/src/output/ts_emitter.ts

@@ -44,40 +44,38 @@ export function debugOutputAstAsTypeScript(ast: o.Statement | o.Expression | o.T
 export class TypeScriptEmitter implements OutputEmitter {
   constructor(private _importResolver: ImportResolver) {}
 
-  emitStatements(genFilePath: string, stmts: o.Statement[], exportedVars: string[]): string {
+  emitStatements(
+      srcFilePath: string, genFilePath: string, stmts: o.Statement[], exportedVars: string[],
+      preamble: string = ''): string {
     const converter = new _TsEmitterVisitor(genFilePath, this._importResolver);
 
     const ctx = EmitterVisitorContext.createRoot(exportedVars);
 
     converter.visitAllStatements(stmts, ctx);
 
-    const srcParts: string[] = [];
-
+    const preambleLines = preamble ? preamble.split('\n') : [];
     converter.reexports.forEach((reexports, exportedFilePath) => {
       const reexportsCode =
           reexports.map(reexport => `${reexport.name} as ${reexport.as}`).join(',');
-      srcParts.push(
+      preambleLines.push(
           `export {${reexportsCode}} from '${this._importResolver.fileNameToModuleName(exportedFilePath, genFilePath)}';`);
     });
 
     converter.importsWithPrefixes.forEach((prefix, importedFilePath) => {
       // Note: can't write the real word for import as it screws up system.js auto detection...
-      srcParts.push(
+      preambleLines.push(
           `imp` +
           `ort * as ${prefix} from '${this._importResolver.fileNameToModuleName(importedFilePath, genFilePath)}';`);
     });
 
-    srcParts.push(ctx.toSource());
-
-    const prefixLines = converter.reexports.size + converter.importsWithPrefixes.size;
-    const sm = ctx.toSourceMapGenerator(genFilePath, prefixLines).toJsComment();
+    const sm =
+        ctx.toSourceMapGenerator(srcFilePath, genFilePath, preambleLines.length).toJsComment();
+    const lines = [...preambleLines, ctx.toSource(), sm];
     if (sm) {
-      srcParts.push(sm);
+      // always add a newline at the end, as some tools have bugs without it.
+      lines.push('');
     }
-    // always add a newline at the end, as some tools have bugs without it.
-    srcParts.push('');
-
-    return srcParts.join('\n');
+    return lines.join('\n');
   }
 }