Error on export default of type: issue https://github.com/microsoft/TypeScript/issues/55087 #55097

EliLichtblau · 2023-07-21T03:29:22Z

Fixes: #55087
This changes the behavior of TS to the specified behavior in issue.

Export default of types become errors - i.e

type foo = 3
export default foo

This is because if it does not error - typescript emits invalid code.

typescript-bot · 2023-07-21T03:29:35Z

This PR doesn't have any linked issues. Please open an issue that references this PR. From there we can discuss and prioritise.

EliLichtblau · 2023-07-21T03:31:08Z

@microsoft-github-policy-service agree

EliLichtblau · 2023-07-21T03:36:06Z

Fixes: #55087

trying to trigger link issue

fatcerberus · 2023-07-21T16:04:35Z

FWIW I think it's okay to default-export types in general, as long as they only have a typespace meaning--the problem is when you default-export something that has a valuespace meaning (like a class) which has been imported via import type.

EliLichtblau · 2023-07-23T05:03:30Z

If this is the only condition - I think you can just convert

 if (!isIllegalExportDefaultInCJS && !(node.flags & NodeFlags.Ambient) && compilerOptions.verbatimModuleSyntax && getTypeOnlyAliasDeclaration(sym, SymbolFlags.Value)) {

to

if (!(node.flags & NodeFlags.Ambient) && getTypeOnlyAliasDeclaration(sym, SymbolFlags.Value)) {

the reason I find this a little awkward is checking with ts-fork-typechecker but emitting with ts loader transpileOnly is pretty common and you can pass the typechecking stage and still emit invalid code as the following code:

ts.transpileModule(`
import {type Node} from "typescript"
export default Node
`, {})

will give you

export default Node

even though Node is an interface. I can understand why you (the TS team) would say this is improper use and shouldn't be supported though.

With that said, my take is:

There should be a flag which disables all export default of things (need a better word here sorry) imported in a typeOnly context as this can emit invalid code with transpileModule calls
The check on export default of import types should not live behind the verbatim module syntax flag and should be default behavior

But I will implement whatever you think is best

The best solution IMO is to not change compile time behavior at all and for emit to just work but based on your comments in the issue I am unsure if this is possible. I know less than little about the emit phase so I don't have any idea here.

andrewbranch

I think the expected behavior is

an export default of a type-only import never emits anything
it’s an error only in isolatedModule (ts1205)

andrewbranch · 2023-11-13T20:28:52Z

Fixed the checker behavior, still need to fix the emit. (Disregard the review request, I jumped the gun.)

andrewbranch · 2023-11-13T20:48:14Z

Ok, ready.

jakebailey

LGTM but should get the extended test run.

jakebailey · 2023-11-13T20:51:30Z

tests/baselines/reference/exportDefault.js

@@ -41,7 +41,6 @@ exports.A = A;
 //// [b.js]
 "use strict";
 Object.defineProperty(exports, "__esModule", { value: true });
-exports.default = types;


jakebailey · 2023-11-13T20:56:12Z

@typescript-bot test top200
@typescript-bot user test this
@typescript-bot run dt

@typescript-bot perf test this

typescript-bot · 2023-11-13T20:56:15Z

Heya @jakebailey, I've started to run the parallelized Definitely Typed test suite on this PR at 12f9ae6. You can monitor the build here.

Update: The results are in!

typescript-bot · 2023-11-13T20:56:15Z

Heya @jakebailey, I've started to run the diff-based top-repos suite on this PR at 12f9ae6. You can monitor the build here.

Update: The results are in!

typescript-bot · 2023-11-13T20:56:15Z

Heya @jakebailey, I've started to run the regular perf test suite on this PR at 12f9ae6. You can monitor the build here.

Update: The results are in!

typescript-bot · 2023-11-13T20:56:15Z

Heya @jakebailey, I've started to run the diff-based user code test suite on this PR at 12f9ae6. You can monitor the build here.

Update: The results are in!

typescript-bot · 2023-11-13T21:14:05Z

@jakebailey Here are the results of running the user test suite comparing main and refs/pull/55097/merge:

There were infrastructure failures potentially unrelated to your change:

2 instances of "Package install failed"

Otherwise...

Something interesting changed - please have a look.

Details

puppeteer

packages/browsers/test/src/tsconfig.json

[MISSING] error TS2307: Cannot find module '@pptr/testserver' or its corresponding type declarations.
- packages/browsers/test/src/utils.ts#L23 in packages/browsers/test/src/tsconfig.json

typescript-bot · 2023-11-13T21:22:21Z

@jakebailey
The results of the perf run you requested are in!

Here they are:

Compiler

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{Angular - node (v18.15.0, x64)}
_{Memory used}	_{295,141k (± 0.02%)}	_{295,178k (± 0.02%)}	_~	_295,102k	_295,242k	_{p=0.336 n=6}
_{Parse Time}	_{2.62s (± 0.67%)}	_{2.62s (± 0.52%)}	_~	_2.60s	_2.64s	_{p=0.867 n=6}
_{Bind Time}	_{0.84s (± 1.30%)}	_{0.83s (± 0.49%)}	_~	_0.83s	_0.84s	_{p=0.178 n=6}
_{Check Time}	_{8.07s (± 0.17%)}	_{8.04s (± 0.26%)}	_~	_8.01s	_8.06s	_{p=0.056 n=6}
_{Emit Time}	_{7.07s (± 0.31%)}	_{7.10s (± 0.65%)}	_~	_7.06s	_7.18s	_{p=0.746 n=6}
_{Total Time}	_{18.61s (± 0.04%)}	_{18.60s (± 0.25%)}	_~	_18.54s	_18.68s	_{p=0.328 n=6}
_{Compiler-Unions - node (v18.15.0, x64)}
_{Memory used}	_{193,619k (± 1.65%)}	_{190,691k (± 0.01%)}	_~	_190,661k	_190,718k	_{p=0.128 n=6}
_{Parse Time}	_{1.35s (± 0.61%)}	_{1.35s (± 0.90%)}	_~	_1.35s	_1.38s	_{p=0.218 n=6}
_{Bind Time}	_{0.73s (± 0.00%)}	_{0.73s (± 0.56%)}	_~	_0.73s	_0.74s	_{p=0.405 n=6}
_{Check Time}	_{9.13s (± 0.43%)}	_{9.18s (± 0.36%)}	_{+0.05s (+ 0.49%)}	_9.14s	_9.22s	_{p=0.044 n=6}
_{Emit Time}	_{2.62s (± 0.48%)}	_{2.62s (± 0.59%)}	_~	_2.60s	_2.64s	_{p=1.000 n=6}
_{Total Time}	_{13.83s (± 0.31%)}	_{13.88s (± 0.16%)}	_~	_13.85s	_13.91s	_{p=0.053 n=6}
_{Monaco - node (v18.15.0, x64)}
_{Memory used}	_{347,343k (± 0.01%)}	_{347,372k (± 0.01%)}	_~	_347,347k	_347,408k	_{p=0.054 n=6}
_{Parse Time}	_{2.46s (± 0.49%)}	_{2.46s (± 0.72%)}	_~	_2.43s	_2.48s	_{p=0.935 n=6}
_{Bind Time}	_{0.94s (± 0.67%)}	_{0.94s (± 0.43%)}	_~	_0.94s	_0.95s	_{p=0.673 n=6}
_{Check Time}	_{6.92s (± 0.66%)}	_{6.93s (± 0.27%)}	_~	_6.90s	_6.95s	_{p=0.222 n=6}
_{Emit Time}	_{4.05s (± 0.34%)}	_{4.06s (± 0.61%)}	_~	_4.04s	_4.09s	_{p=0.745 n=6}
_{Total Time}	_{14.37s (± 0.36%)}	_{14.39s (± 0.25%)}	_~	_14.36s	_14.46s	_{p=0.226 n=6}
_{TFS - node (v18.15.0, x64)}
_{Memory used}	_{302,592k (± 0.00%)}	_{302,606k (± 0.01%)}	_~	_302,583k	_302,674k	_{p=0.468 n=6}
_{Parse Time}	_{1.99s (± 0.99%)}	_{1.99s (± 0.74%)}	_~	_1.97s	_2.01s	_{p=0.934 n=6}
_{Bind Time}	_{1.01s (± 1.02%)}	_{1.01s (± 0.74%)}	_~	_1.00s	_1.02s	_{p=0.437 n=6}
_{Check Time}	_{6.25s (± 0.41%)}	_{6.25s (± 0.36%)}	_~	_6.22s	_6.28s	_{p=0.808 n=6}
_{Emit Time}	_{3.58s (± 0.62%)}	_{3.58s (± 0.57%)}	_~	_3.56s	_3.61s	_{p=0.871 n=6}
_{Total Time}	_{12.83s (± 0.37%)}	_{12.84s (± 0.33%)}	_~	_12.80s	_12.92s	_{p=1.000 n=6}
_{material-ui - node (v18.15.0, x64)}
_{Memory used}	_{470,568k (± 0.01%)}	_{470,574k (± 0.00%)}	_~	_470,553k	_470,592k	_{p=0.689 n=6}
_{Parse Time}	_{2.56s (± 0.68%)}	_{2.57s (± 0.78%)}	_~	_2.54s	_2.60s	_{p=0.567 n=6}
_{Bind Time}	_{0.98s (± 1.23%)}	_{0.99s (± 0.52%)}	_~	_0.99s	_1.00s	_{p=0.142 n=6}
_{Check Time}	_{16.68s (± 0.40%)}	_{16.65s (± 0.55%)}	_~	_16.58s	_16.83s	_{p=0.334 n=6}
_{Emit Time}	_{0.00s (± 0.00%)}	_{0.00s (± 0.00%)}	_~	_0.00s	_0.00s	_{p=1.000 n=6}
_{Total Time}	_{20.23s (± 0.26%)}	_{20.21s (± 0.46%)}	_~	_20.14s	_20.40s	_{p=0.228 n=6}
_{xstate - node (v18.15.0, x64)}
_{Memory used}	_{512,837k (± 0.01%)}	_{512,827k (± 0.02%)}	_~	_512,743k	_512,956k	_{p=0.810 n=6}
_{Parse Time}	_{3.27s (± 0.23%)}	_{3.27s (± 0.16%)}	_~	_3.27s	_3.28s	_{p=0.784 n=6}
_{Bind Time}	_{1.54s (± 0.35%)}	_{1.54s (± 0.82%)}	_~	_1.53s	_1.56s	_{p=0.357 n=6}
_{Check Time}	_{2.86s (± 0.68%)}	_{2.86s (± 0.69%)}	_~	_2.85s	_2.90s	_{p=0.747 n=6}
_{Emit Time}	_{0.08s (± 0.00%)}	_{0.08s (± 0.00%)}	_~	_0.08s	_0.08s	_{p=1.000 n=6}
_{Total Time}	_{7.75s (± 0.23%)}	_{7.75s (± 0.21%)}	_~	_7.73s	_7.78s	_{p=1.000 n=6}

System info unknown

Hosts

node (v18.15.0, x64)

Scenarios

Angular - node (v18.15.0, x64)
Compiler-Unions - node (v18.15.0, x64)
Monaco - node (v18.15.0, x64)
TFS - node (v18.15.0, x64)
material-ui - node (v18.15.0, x64)
xstate - node (v18.15.0, x64)

_Benchmark	_Name	_Iterations
_Current	_pr	₆
_Baseline	_baseline	₆

tsserver

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{Compiler-UnionsTSServer - node (v18.15.0, x64)}
_{Req 1 - updateOpen}	_{2,377ms (± 1.04%)}	_{2,372ms (± 1.05%)}	_~	_2,329ms	_2,392ms	_{p=0.809 n=6}
_{Req 2 - geterr}	_{5,367ms (± 1.43%)}	_{5,364ms (± 1.64%)}	_~	_5,285ms	_5,476ms	_{p=0.748 n=6}
_{Req 3 - references}	_{328ms (± 1.39%)}	_{326ms (± 0.53%)}	_~	_323ms	_328ms	_{p=0.935 n=6}
_{Req 4 - navto}	_{277ms (± 1.05%)}	_{277ms (± 0.98%)}	_~	_273ms	_279ms	_{p=0.867 n=6}
_{Req 5 - completionInfo count}	_{1,356 (± 0.00%)}	_{1,356 (± 0.00%)}	_~	_1,356	_1,356	_{p=1.000 n=6}
_{Req 5 - completionInfo}	_{83ms (± 7.99%)}	_{81ms (± 8.64%)}	_~	_75ms	_90ms	_{p=0.563 n=6}
_{CompilerTSServer - node (v18.15.0, x64)}
_{Req 1 - updateOpen}	_{2,499ms (± 0.66%)}	_{2,502ms (± 0.72%)}	_~	_2,473ms	_2,527ms	_{p=0.471 n=6}
_{Req 2 - geterr}	_{4,056ms (± 1.55%)}	_{4,082ms (± 1.83%)}	_~	_4,027ms	_4,178ms	_{p=0.469 n=6}
_{Req 3 - references}	_{343ms (± 1.23%)}	_{340ms (± 1.70%)}	_~	_333ms	_345ms	_{p=0.565 n=6}
_{Req 4 - navto}	_{283ms (± 0.37%)}	_{282ms (± 0.32%)}	_~	_281ms	_283ms	_{p=0.273 n=6}
_{Req 5 - completionInfo count}	_{1,518 (± 0.00%)}	_{1,518 (± 0.00%)}	_~	_1,518	_1,518	_{p=1.000 n=6}
_{Req 5 - completionInfo}	_{88ms (± 5.56%)}	_{86ms (± 6.77%)}	_~	_78ms	_90ms	_{p=0.390 n=6}
_{xstateTSServer - node (v18.15.0, x64)}
_{Req 1 - updateOpen}	_{2,592ms (± 0.40%)}	_{2,589ms (± 0.46%)}	_~	_2,571ms	_2,604ms	_{p=0.809 n=6}
_{Req 2 - geterr}	_{1,720ms (± 2.03%)}	_{1,718ms (± 2.54%)}	_~	_1,674ms	_1,766ms	_{p=0.873 n=6}
_{Req 3 - references}	_{109ms (± 7.35%)}	_{111ms (± 9.02%)}	_~	_101ms	_122ms	_{p=1.000 n=6}
_{Req 4 - navto}	_{366ms (± 0.52%)}	_{368ms (± 1.27%)}	_~	_365ms	_377ms	_{p=0.564 n=6}
_{Req 5 - completionInfo count}	_{2,073 (± 0.00%)}	_{2,073 (± 0.00%)}	_~	_2,073	_2,073	_{p=1.000 n=6}
_{Req 5 - completionInfo}	_{311ms (± 2.08%)}	_{308ms (± 2.50%)}	_~	_299ms	_318ms	_{p=0.686 n=6}

System info unknown

Hosts

node (v18.15.0, x64)

Scenarios

CompilerTSServer - node (v18.15.0, x64)
Compiler-UnionsTSServer - node (v18.15.0, x64)
xstateTSServer - node (v18.15.0, x64)

_Benchmark	_Name	_Iterations
_Current	_pr	₆
_Baseline	_baseline	₆

Startup

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{tsc-startup - node (v18.15.0, x64)}
_{Execution time}	_{152.71ms (± 0.18%)}	_{152.72ms (± 0.19%)}	_~	_151.55ms	_155.92ms	_{p=0.960 n=600}
_{tsserver-startup - node (v18.15.0, x64)}
_{Execution time}	_{227.96ms (± 0.16%)}	_{227.67ms (± 0.15%)}	_{-0.29ms (- 0.13%)}	_226.32ms	_232.50ms	_{p=0.000 n=600}
_{tsserverlibrary-startup - node (v18.15.0, x64)}
_{Execution time}	_{229.56ms (± 0.17%)}	_{229.53ms (± 0.16%)}	_~	_227.86ms	_234.24ms	_{p=0.428 n=600}
_{typescript-startup - node (v18.15.0, x64)}
_{Execution time}	_{229.30ms (± 0.16%)}	_{229.37ms (± 0.16%)}	_{+0.06ms (+ 0.03%)}	_227.87ms	_236.46ms	_{p=0.046 n=600}

System info unknown

Hosts

node (v18.15.0, x64)

Scenarios

tsc-startup - node (v18.15.0, x64)
tsserver-startup - node (v18.15.0, x64)
tsserverlibrary-startup - node (v18.15.0, x64)
typescript-startup - node (v18.15.0, x64)

_Benchmark	_Name	_Iterations
_Current	_pr	₆
_Baseline	_baseline	₆

Developer Information:

Download Benchmarks

typescript-bot · 2023-11-13T21:48:24Z

Hey @jakebailey, the results of running the DT tests are ready.
Everything looks the same!
You can check the log here.

typescript-bot · 2023-11-13T23:17:41Z

@jakebailey Here are the results of running the top-repos suite comparing main and refs/pull/55097/merge:

Something interesting changed - please have a look.

Details

heyxyz/hey

apps/prerender/tsconfig.json

error TS1292: 'Profile' resolves to a type and must be marked type-only in this file before re-exporting when 'isolatedModules' is enabled. Consider using 'export type { Profile as default }'.
- apps/prerender/src/pages/u/[handle].tsx#L63

microsoft/playwright

5 of 15 projects failed to build with the old tsc and were ignored

packages/recorder/tsconfig.json

error TS1292: 'codemirror' resolves to a type and must be marked type-only in this file before re-exporting when 'isolatedModules' is enabled. Consider using 'export type { codemirror as default }'.
- packages/web/src/components/codeMirrorModule.tsx#L28

andrewbranch · 2023-11-17T21:37:26Z

These errors from the top repos look possibly wrong, especially the playwright one. Need to take a closer look.

andrewbranch · 2023-11-17T21:51:14Z

@typescript-bot test top200

typescript-bot · 2023-11-17T21:51:18Z

Heya @andrewbranch, I've started to run the diff-based top-repos suite on this PR at 7b2dee6. You can monitor the build here.

Update: The results are in!

jakebailey · 2023-11-17T22:02:06Z

You can ignore that playwright one, that is currently happening on every PR and we just haven't looked at why.

andrewbranch · 2023-11-17T22:05:39Z

Huh? The playwright one is clearly caused by this and fixed in the latest commit.

jakebailey · 2023-11-17T22:07:31Z

Apologies, I mixed up the "P" libraries and confused playwright for puppeteer (which you can see on other PRs like #56429 (comment)). Ignore me!

typescript-bot · 2023-11-17T23:53:31Z

@andrewbranch Here are the results of running the top-repos suite comparing main and refs/pull/55097/merge:

Everything looks good!

Change and tests accepted

1f5a5b0

typescript-bot added the For Uncommitted Bug PR for untriaged, rejected, closed or missing bug label Jul 21, 2023

fix lint

c5494a1

sandersn requested review from andrewbranch and sheetalkamat August 4, 2023 23:34

sandersn assigned andrewbranch Aug 4, 2023

andrewbranch requested changes Aug 5, 2023

View reviewed changes

andrewbranch added 2 commits November 13, 2023 11:13

Merge branch 'main' into eli/no-type-default-exports

9ee5472

Add tests and fix implementation

75a4c20

andrewbranch requested a review from jakebailey November 13, 2023 20:27

andrewbranch added 2 commits November 13, 2023 12:30

Remove unnecessary parts of baseline

981a1fd

Fix export assignment emit

12f9ae6

jakebailey approved these changes Nov 13, 2023

View reviewed changes

Delete old baselines

7064af4

andrewbranch mentioned this pull request Nov 17, 2023

Elide re-exports of unresolved type-only imports #56449

Merged

Fix false error on unresolved import

7b2dee6

andrewbranch added 2 commits November 17, 2023 14:49

Merge branch 'main' into eli/no-type-default-exports

392167d

Update baseline with change from main

6f27b59

andrewbranch merged commit 9063d7b into microsoft:main Nov 20, 2023
19 checks passed

andrewbranch mentioned this pull request Jan 23, 2024

Fix isolatedModules check for export assignments #57148

Merged

Error on export default of type: issue https://github.com/microsoft/TypeScript/issues/55087 #55097

Error on export default of type: issue https://github.com/microsoft/TypeScript/issues/55087 #55097

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Compiler

tsserver

Startup

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