diff --git a/packages/bazel/src/ngc-wrapped/index.ts b/packages/bazel/src/ngc-wrapped/index.ts
index bf605271c1..85db0169d1 100644
--- a/packages/bazel/src/ngc-wrapped/index.ts
+++ b/packages/bazel/src/ngc-wrapped/index.ts
@@ -78,8 +78,9 @@ export function compile({allowNonHermeticReads, compilerOpts, tsHost, bazelOpts,
   expectedOuts: string[], gatherDiagnostics?: (program: ng.Program) => ng.Diagnostics
 }): {diagnostics: ng.Diagnostics, program: ng.Program} {
   let fileLoader: FileLoader;
+
   if (inputs) {
-    fileLoader = new CachedFileLoader(fileCache, ALLOW_NON_HERMETIC_READS);
+    fileLoader = new CachedFileLoader(fileCache, allowNonHermeticReads);
     // Resolve the inputs to absolute paths to match TypeScript internals
     const resolvedInputs: {[path: string]: string} = {};
     for (const key of Object.keys(inputs)) {
@@ -141,10 +142,8 @@ export function compile({allowNonHermeticReads, compilerOpts, tsHost, bazelOpts,
         moduleName, containingFile, compilerOptions, generatedFileModuleResolverHost);
   }
 
-  // TODO(alexeagle): does this also work in third_party?
-  const allowNonHermeticRead = false;
   const bazelHost = new CompilerHost(
-      files, compilerOpts, bazelOpts, tsHost, fileLoader, ALLOW_NON_HERMETIC_READS,
+      files, compilerOpts, bazelOpts, tsHost, fileLoader, allowNonHermeticReads,
       generatedFileModuleResolver);
   const origBazelHostFileExist = bazelHost.fileExists;
   bazelHost.fileExists = (fileName: string) => {
@@ -179,6 +178,10 @@ export function compile({allowNonHermeticReads, compilerOpts, tsHost, bazelOpts,
             ],
           });
 
+  if (!gatherDiagnostics) {
+    gatherDiagnostics = (program) =>
+        gatherDiagnosticsForInputsOnly(compilerOpts, bazelOpts, program);
+  }
   const {diagnostics, emitResult, program} = ng.performCompilation(
       {rootNames: files, options: compilerOpts, host: ngHost, emitCallback, gatherDiagnostics});
   const tsickleEmitResult = emitResult as tsickle.EmitResult;
@@ -209,6 +212,36 @@ export function compile({allowNonHermeticReads, compilerOpts, tsHost, bazelOpts,
   return {program, diagnostics};
 }
 
+function isCompilationTarget(bazelOpts: BazelOptions, sf: ts.SourceFile): boolean {
+  return !NGC_GEN_FILES.test(sf.fileName) &&
+      (bazelOpts.compilationTargetSrc.indexOf(sf.fileName) !== -1);
+}
+
+function gatherDiagnosticsForInputsOnly(
+    options: ng.CompilerOptions, bazelOpts: BazelOptions,
+    ngProgram: ng.Program): (ng.Diagnostic | ts.Diagnostic)[] {
+  const tsProgram = ngProgram.getTsProgram();
+  const diagnostics: (ng.Diagnostic | ts.Diagnostic)[] = [];
+  // These checks mirror ts.getPreEmitDiagnostics, with the important
+  // exception of avoiding b/30708240, which is that if you call
+  // program.getDeclarationDiagnostics() it somehow corrupts the emit.
+  diagnostics.push(...tsProgram.getOptionsDiagnostics());
+  diagnostics.push(...tsProgram.getGlobalDiagnostics());
+  for (const sf of tsProgram.getSourceFiles().filter(f => isCompilationTarget(bazelOpts, f))) {
+    // Note: We only get the diagnostics for individual files
+    // to e.g. not check libraries.
+    diagnostics.push(...tsProgram.getSyntacticDiagnostics(sf));
+    diagnostics.push(...tsProgram.getSemanticDiagnostics(sf));
+  }
+  if (!diagnostics.length) {
+    // only gather the angular diagnostics if we have no diagnostics
+    // in any other files.
+    diagnostics.push(...ngProgram.getNgStructuralDiagnostics());
+    diagnostics.push(...ngProgram.getNgSemanticDiagnostics());
+  }
+  return diagnostics;
+}
+
 if (require.main === module) {
   process.exitCode = main(process.argv.slice(2));
 }
diff --git a/packages/compiler-cli/src/transformers/program.ts b/packages/compiler-cli/src/transformers/program.ts
index e2deb7c13a..a84fd695d3 100644
--- a/packages/compiler-cli/src/transformers/program.ts
+++ b/packages/compiler-cli/src/transformers/program.ts
@@ -56,7 +56,6 @@ class AngularCompilerProgram implements Program {
   private _analyzedModules: NgAnalyzedModules|undefined;
   private _structuralDiagnostics: Diagnostic[]|undefined;
   private _programWithStubs: ts.Program|undefined;
-  private _semanticDiagnostics: {ts: ts.Diagnostic[], ng: Diagnostic[]}|undefined;
   private _optionsDiagnostics: Diagnostic[] = [];
 
   constructor(
@@ -148,12 +147,28 @@ class AngularCompilerProgram implements Program {
 
   getTsSemanticDiagnostics(sourceFile?: ts.SourceFile, cancellationToken?: ts.CancellationToken):
       ts.Diagnostic[] {
-    return this.semanticDiagnostics.ts;
+    if (sourceFile) {
+      return this.tsProgram.getSemanticDiagnostics(sourceFile, cancellationToken);
+    }
+    let diags: ts.Diagnostic[] = [];
+    this.tsProgram.getSourceFiles().forEach(sf => {
+      if (!GENERATED_FILES.test(sf.fileName)) {
+        diags.push(...this.tsProgram.getSemanticDiagnostics(sf, cancellationToken));
+      }
+    });
+    return diags;
   }
 
   getNgSemanticDiagnostics(fileName?: string, cancellationToken?: ts.CancellationToken):
       Diagnostic[] {
-    return this.semanticDiagnostics.ng;
+    let diags: ts.Diagnostic[] = [];
+    this.tsProgram.getSourceFiles().forEach(sf => {
+      if (GENERATED_FILES.test(sf.fileName) && !sf.isDeclarationFile) {
+        diags.push(...this.tsProgram.getSemanticDiagnostics(sf, cancellationToken));
+      }
+    });
+    const {ng} = translateDiagnostics(this.typeCheckHost, diags);
+    return ng;
   }
 
   loadNgStructureAsync(): Promise<void> {
@@ -359,11 +374,6 @@ class AngularCompilerProgram implements Program {
     return this._typeCheckHost !;
   }
 
-  private get semanticDiagnostics(): {ts: ts.Diagnostic[], ng: Diagnostic[]} {
-    return this._semanticDiagnostics ||
-        (this._semanticDiagnostics = this.generateSemanticDiagnostics());
-  }
-
   private calculateTransforms(
       genFiles: Map<string, GeneratedFile>,
       customTransformers?: CustomTransformers): ts.CustomTransformers {
@@ -546,10 +556,6 @@ class AngularCompilerProgram implements Program {
     return sourceFilesToEmit;
   }
 
-  private generateSemanticDiagnostics(): {ts: ts.Diagnostic[], ng: Diagnostic[]} {
-    return translateDiagnostics(this.typeCheckHost, this.tsProgram.getSemanticDiagnostics());
-  }
-
   private writeFile(
       outFileName: string, outData: string, writeByteOrderMark: boolean,
       onError?: (message: string) => void, genFile?: GeneratedFile, sourceFiles?: ts.SourceFile[]) {