perf(compiler): only emit changed files for incremental compilation

For now, we always create all generated files, but diff them
before we pass them to TypeScript.

For the user files, we compare the programs and only emit changed
TypeScript files.

This also adds more diagnostic messages if the `—diagnostics` flag
is passed to the command line.

packages/compiler-cli/src/ngtools_api2.ts

@@ -19,9 +19,11 @@ import {ParseSourceSpan} from '@angular/compiler';
 import * as ts from 'typescript';
 
 import {formatDiagnostics as formatDiagnosticsOrig} from './perform_compile';
+import {Program as ProgramOrig} from './transformers/api';
 import {createCompilerHost as createCompilerOrig} from './transformers/compiler_host';
 import {createProgram as createProgramOrig} from './transformers/program';
 
+
 // Interfaces from ./transformers/api;
 export interface Diagnostic {
   messageText: string;
@@ -92,12 +94,6 @@ export interface TsEmitArguments {
 
 export interface TsEmitCallback { (args: TsEmitArguments): ts.EmitResult; }
 
-export interface LibrarySummary {
-  fileName: string;
-  text: string;
-  sourceFile?: ts.SourceFile;
-}
-
 export interface Program {
   getTsProgram(): ts.Program;
   getTsOptionDiagnostics(cancellationToken?: ts.CancellationToken): ts.Diagnostic[];
@@ -116,7 +112,6 @@ export interface Program {
     customTransformers?: CustomTransformers,
     emitCallback?: TsEmitCallback
   }): ts.EmitResult;
-  getLibrarySummaries(): LibrarySummary[];
 }
 
 // Wrapper for createProgram.
@@ -124,7 +119,7 @@ export function createProgram(
     {rootNames, options, host, oldProgram}:
         {rootNames: string[], options: CompilerOptions, host: CompilerHost, oldProgram?: Program}):
     Program {
-  return createProgramOrig({rootNames, options, host, oldProgram});
+  return createProgramOrig({rootNames, options, host, oldProgram: oldProgram as ProgramOrig});
 }
 
 // Wrapper for createCompilerHost.