From 4f7c971ee726ef17a3b080db0f71a41de402f066 Mon Sep 17 00:00:00 2001
From: Paul Gschwendtner <paulgschwendtner@gmail.com>
Date: Wed, 21 Aug 2019 20:51:24 +0200
Subject: [PATCH] fix(ivy): ngtsc throws if "flatModuleOutFile" is set to null
 (#32235)

In ngc is was valid to set the "flatModuleOutFile" option to "null". This is sometimes
necessary if a tsconfig extends from another one but the "fatModuleOutFile" option
needs to be unset (note that "undefined" does not exist as value in JSON)

Now if ngtsc is used to compile the project, ngtsc will fail with an error because it
tries to do string manipulation on the "flatModuleOutFile". This happens because
ngtsc only skips flat module indices if the option is set to "undefined".

Since this is not compatible with what was supported in ngc and such exceptions
should be avoided, the flat module check is now aligned with ngc.

```
TypeError: Cannot read property 'replace' of null
    at Object.normalizeSeparators (/home/circleci/project/node_modules/@angular/compiler-cli/src/ngtsc/util/src/path.js:35:21)
    at new NgtscProgram (/home/circleci/project/node_modules/@angular/compiler-cli/src/ngtsc/program.js:126:52)
```

Additionally setting the `flatModuleOutFile` option to an empty string
currently results in unexpected behavior. No errors is thrown, but the
flat module index file will be `.ts` (no file name; just extension).

This is now also fixed by treating an empty string similarly to
`null`.

PR Close #32235
---
 packages/compiler-cli/src/ngtsc/program.ts    |  2 +-
 packages/compiler-cli/test/ngtsc/env.ts       |  3 +-
 .../compiler-cli/test/ngtsc/ngtsc_spec.ts     | 29 +++++++++++++++++++
 3 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/packages/compiler-cli/src/ngtsc/program.ts b/packages/compiler-cli/src/ngtsc/program.ts
index 57e0e706fe..4c53cc12f2 100644
--- a/packages/compiler-cli/src/ngtsc/program.ts
+++ b/packages/compiler-cli/src/ngtsc/program.ts
@@ -116,7 +116,7 @@ export class NgtscProgram implements api.Program {
     rootFiles.push(this.typeCheckFilePath);
 
     let entryPoint: AbsoluteFsPath|null = null;
-    if (options.flatModuleOutFile !== undefined) {
+    if (options.flatModuleOutFile != null && options.flatModuleOutFile !== '') {
       entryPoint = findFlatIndexEntryPoint(normalizedRootNames);
       if (entryPoint === null) {
         // This error message talks specifically about having a single .ts file in "files". However
diff --git a/packages/compiler-cli/test/ngtsc/env.ts b/packages/compiler-cli/test/ngtsc/env.ts
index 445c70e569..cf274ab618 100644
--- a/packages/compiler-cli/test/ngtsc/env.ts
+++ b/packages/compiler-cli/test/ngtsc/env.ts
@@ -145,7 +145,8 @@ export class NgtscTestEnvironment {
     this.multiCompileHostExt.invalidate(absFilePath);
   }
 
-  tsconfig(extraOpts: {[key: string]: string | boolean} = {}, extraRootDirs?: string[]): void {
+  tsconfig(extraOpts: {[key: string]: string | boolean | null} = {}, extraRootDirs?: string[]):
+      void {
     const tsconfig: {[key: string]: any} = {
       extends: './tsconfig-base.json',
       angularCompilerOptions: {...extraOpts, enableIvy: true},
diff --git a/packages/compiler-cli/test/ngtsc/ngtsc_spec.ts b/packages/compiler-cli/test/ngtsc/ngtsc_spec.ts
index 018353e709..d1daf105f5 100644
--- a/packages/compiler-cli/test/ngtsc/ngtsc_spec.ts
+++ b/packages/compiler-cli/test/ngtsc/ngtsc_spec.ts
@@ -2967,6 +2967,35 @@ runInEachFileSystem(os => {
         expect(env.getContents('./public-api/index.js')).toContain(`export * from '../test';`);
       });
 
+      it('should not throw if "flatModuleOutFile" is set to null', () => {
+        env.tsconfig({
+          'flatModuleOutFile': null,
+        });
+
+        env.write('test.ts', `export const SOME_EXPORT = 'some-export'`);
+        // The "driveMain" method automatically ensures that there is no
+        // exception and that the build succeeded.
+        env.driveMain();
+      });
+
+      it('should not throw or produce flat module index if "flatModuleOutFile" is set to ' +
+             'empty string',
+         () => {
+           env.tsconfig({
+             'flatModuleOutFile': '',
+           });
+
+           env.write('test.ts', `export const SOME_EXPORT = 'some-export'`);
+           // The "driveMain" method automatically ensures that there is no
+           // exception and that the build succeeded.
+           env.driveMain();
+           // Previously ngtsc incorrectly tried generating a flat module index
+           // file if the "flatModuleOutFile" was set to an empty string. ngtsc
+           // just wrote the bundle file with an empty filename (just extension).
+           env.assertDoesNotExist('.js');
+           env.assertDoesNotExist('.d.ts');
+         });
+
       it('should report an error when a flat module index is requested but no entrypoint can be determined',
          () => {
            env.tsconfig({'flatModuleOutFile': 'flat.js'});