From dc9a066f65f713daefbb61ecd6b0557af430ab3d Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <293473+sandersn@users.noreply.github.com>
Date: Thu, 25 Oct 2018 15:08:06 -0700
Subject: [PATCH] Do not merge commonJS exports into an alias (#28133)

* Do not merge commonsjs exports onto an alias

getCommonJSExportEquals merges export assignments and export property
assignments. Something like this, which has no equivalent structure in
TS:

```js
module.exports = function() { }
module.exports.expando = 1
```

However, it is sometimes called with an alias, when its
parent, resolveExternalModuleSymbol, is called with dontResolveAlias:
true, and when the initialiser of the export assignment is an alias:

```js
function alias() { }
module.exports = alias
module.exports.expando = 1
```

In this case, (1) the actual value `alias` will have already merged in a
previous call to getCommonJSExportEquals and
(2) getTypeOfSymbol will follow the alias symbol to get the right type.
So getCommonJSExportEquals should do nothing in this case.

This bug manifests in the code for dynamic imports, which calls
getTypeOfSymbol on the incorrectly merged alias, which now has enough
value flags--Function, for example--to take the wrong branch and
subsequently crash.

* Update baselines
---
 src/compiler/checker.ts                       |  2 +-
 ...errorForConflictingExportEqualsValue.types |  2 +-
 .../moduleExportAliasImported.symbols         | 19 +++++++++++++++
 .../reference/moduleExportAliasImported.types | 23 +++++++++++++++++++
 .../salsa/moduleExportAliasImported.ts        | 12 ++++++++++
 5 files changed, 56 insertions(+), 2 deletions(-)
 create mode 100644 tests/baselines/reference/moduleExportAliasImported.symbols
 create mode 100644 tests/baselines/reference/moduleExportAliasImported.types
 create mode 100644 tests/cases/conformance/salsa/moduleExportAliasImported.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 4305227dab7..49caad2116e 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -2362,7 +2362,7 @@ namespace ts {
         }
 
         function getCommonJsExportEquals(exported: Symbol | undefined, moduleSymbol: Symbol): Symbol | undefined {
-            if (!exported || exported === unknownSymbol || exported === moduleSymbol || moduleSymbol.exports!.size === 1) {
+            if (!exported || exported === unknownSymbol || exported === moduleSymbol || moduleSymbol.exports!.size === 1 || exported.flags & SymbolFlags.Alias) {
                 return exported;
             }
             const merged = cloneSymbol(exported);
diff --git a/tests/baselines/reference/errorForConflictingExportEqualsValue.types b/tests/baselines/reference/errorForConflictingExportEqualsValue.types
index b9915169120..5d2b63f2e9a 100644
--- a/tests/baselines/reference/errorForConflictingExportEqualsValue.types
+++ b/tests/baselines/reference/errorForConflictingExportEqualsValue.types
@@ -6,6 +6,6 @@ export = x;
 >x : any
 
 import("./a");
->import("./a") : Promise<typeof import("/a").x>
+>import("./a") : Promise<any>
 >"./a" : "./a"
 
diff --git a/tests/baselines/reference/moduleExportAliasImported.symbols b/tests/baselines/reference/moduleExportAliasImported.symbols
new file mode 100644
index 00000000000..9649cc0a3b6
--- /dev/null
+++ b/tests/baselines/reference/moduleExportAliasImported.symbols
@@ -0,0 +1,19 @@
+=== tests/cases/conformance/salsa/bug28014.js ===
+exports.version = 1
+>exports.version : Symbol(version)
+>exports : Symbol(version, Decl(bug28014.js, 0, 0))
+>version : Symbol(version, Decl(bug28014.js, 0, 0))
+
+function alias() { }
+>alias : Symbol(alias, Decl(bug28014.js, 0, 19))
+
+module.exports = alias
+>module.exports : Symbol("tests/cases/conformance/salsa/bug28014", Decl(bug28014.js, 0, 0))
+>module : Symbol(export=, Decl(bug28014.js, 1, 20))
+>exports : Symbol(export=, Decl(bug28014.js, 1, 20))
+>alias : Symbol(alias, Decl(bug28014.js, 0, 19))
+
+=== tests/cases/conformance/salsa/importer.js ===
+import('./bug28014')
+>'./bug28014' : Symbol("tests/cases/conformance/salsa/bug28014", Decl(bug28014.js, 0, 0))
+
diff --git a/tests/baselines/reference/moduleExportAliasImported.types b/tests/baselines/reference/moduleExportAliasImported.types
new file mode 100644
index 00000000000..9691acfab22
--- /dev/null
+++ b/tests/baselines/reference/moduleExportAliasImported.types
@@ -0,0 +1,23 @@
+=== tests/cases/conformance/salsa/bug28014.js ===
+exports.version = 1
+>exports.version = 1 : 1
+>exports.version : number
+>exports : typeof alias
+>version : number
+>1 : 1
+
+function alias() { }
+>alias : typeof alias
+
+module.exports = alias
+>module.exports = alias : typeof alias
+>module.exports : typeof alias
+>module : { "tests/cases/conformance/salsa/bug28014": typeof alias; }
+>exports : typeof alias
+>alias : typeof alias
+
+=== tests/cases/conformance/salsa/importer.js ===
+import('./bug28014')
+>import('./bug28014') : Promise<() => void>
+>'./bug28014' : "./bug28014"
+
diff --git a/tests/cases/conformance/salsa/moduleExportAliasImported.ts b/tests/cases/conformance/salsa/moduleExportAliasImported.ts
new file mode 100644
index 00000000000..95c02981382
--- /dev/null
+++ b/tests/cases/conformance/salsa/moduleExportAliasImported.ts
@@ -0,0 +1,12 @@
+// @allowJs: true
+// @noEmit: true
+// @checkJs: true
+// @target: esnext
+// @module: esnext
+// @Filename: bug28014.js
+exports.version = 1
+function alias() { }
+module.exports = alias
+
+// @Filename: importer.js
+import('./bug28014')