VSCode does not show some typescript `isolatedModules` errors

[bradzacher]

Type: Bug

Repro

1. Checkout https://github.com/bradzacher/bug-repros/tree/vscode-typescript-isolatedModules:
   • git clone https://github.com/bradzacher/bug-repros.git
   • git fetch
   • git switch vscode-typescript-isolatedModules
2. Open the folder in vscode
3. Open terminal and install in folder npm i
4. Open package1/index.ts
   • Observe there are no TS errors reported.
5. Open terminal and build npm run build
   • Observe there is a TS build error reported:

> tsc -p ./package1/tsconfig.json

package1/index.ts:3:21 - error TS2748: Cannot access ambient const enums when 'isolatedModules' is enabled.

3 export const test = Foo.Bar;
                      ~~~

Found 1 error in package1/index.ts:3

Expected:

VSCode shows the error when viewing package1/index.ts in the IDE

Actual:

VSCode shows no errors.

---

VS Code version: Code 1.87.2 (Universal) (863d2581ecda6849923a2118d93a088b0745d9d6, 2024-03-08T15:21:31.043Z)
OS version: Darwin arm64 23.4.0
Modes:

System Info

Item	Value
CPUs	Apple M1 Max (10 x 24)
GPU Status	2d_canvas: enabled canvas_oop_rasterization: enabled_on direct_rendering_display_compositor: disabled_off_ok gpu_compositing: enabled multiple_raster_threads: enabled_on opengl: enabled_on rasterization: enabled raw_draw: disabled_off_ok skia_graphite: disabled_off video_decode: enabled video_encode: enabled webgl: enabled webgl2: enabled webgpu: enabled
Load (avg)	2, 2, 3
Memory (System)	64.00GB (20.85GB free)
Process Argv	--crash-reporter-id 4f7fbb36-3a81-40a0-a922-a2a72f77abfa
Screen Reader	no
VM	0%

Extensions (49)

Extension	Author (truncated)	Version
vscode-ndjson	adr	0.100.0
vscode-zipfs	arc	3.0.0
ast-grep-vscode	ast	0.1.3
vscode-bazel	Baz	0.9.0
soysyntaxchecker	Blo	3.30.0
vscode-coloured-status-bar-problems	bra	0.2.0
vscode-copy-filename	bra	0.1.1
npm-intellisense	chr	1.4.5
path-intellisense	chr	2.8.5
vscode-css-modules	cli	0.5.1
coder-remote	cod	0.1.35
vscode-clock	Com	0.0.1
vscode-markdownlint	Dav	0.54.0
vscode-eslint	dba	2.4.4
make-hidden	dev	4.0.4
dprint	dpr	0.16.0
gitlens	eam	14.9.0
EditorConfig	Edi	0.16.4
prettier-vscode	esb	10.1.0
vscode-github-actions	git	0.26.2
vscode-pull-request-github	Git	0.82.0
vscode-graphql	Gra	0.9.3
vscode-graphql-syntax	Gra	1.3.5
nix-ide	jno	0.3.1
statusbarerror	Joe	0.4.0
vscode-json5	mrm	1.0.0
remote-ssh	ms-	0.109.0
remote-ssh-edit	ms-	0.86.0
hexeditor	ms-	1.9.14
remote-explorer	ms-	0.4.3
vscode-js-profile-flame	ms-	1.0.8
vsliveshare	ms-	1.0.5918
vscode-paste-image	mus	1.0.4
inline-sql-syntax	quf	2.16.0
rust-analyzer	rus	0.3.1877
bazel-stack-vscode	Sta	1.9.8
rewrap	stk	1.16.3
code-spell-checker	str	3.0.1
vscode-stylelint	sty	1.3.0
even-better-toml	tam	0.19.2
shellcheck	tim	0.37.0
jest-snapshot-language-support	tle	1.1.1
pdf	tom	1.2.2
vscode-mdx	uni	1.8.2
vscode-lldb	vad	1.10.0
es-quotes	vil	0.2.6
vscode-icons	vsc	12.7.0
vscode-wakatime	Wak	24.4.0
vscode-proto3	zxh	0.5.5

A/B Experiments

vsliv368cf:30146710
vspor879:30202332
vspor708:30202333
vspor363:30204092
vscod805:30301674
binariesv615:30325510
vsaa593cf:30376535
py29gd2263:30899288
c4g48928:30535728
azure-dev_surveyone:30548225
a9j8j154:30646983
962ge761:30959799
pythongtdpath:30769146
welcomedialogc:30910334
pythonidxpt:30866567
pythonnoceb:30805159
asynctok:30898717
pythontestfixt:30902429
pythonregdiag2:30936856
pyreplss1:30897532
pythonmypyd1:30879173
pythoncet0:30885854
pythontbext0:30879054
dsvsc016:30899300
dsvsc017:30899301
dsvsc018:30899302
cppperfnew:30979542
d34g3935:30971562
fegfb526:30981948
bg6jg535:30979843
ccp2r6:30958158
dsvsc020:30976470

[bradzacher]

Note: I'm not sure if this is a vscode or a typescript bug.
The issue specifically manifests within VSCode - hence I'm starting here.

I would assume that there is a breakage here due to the TS project service not properly respecting isolatedModules + project references?

[bradzacher]

It's worth noting that fixing this would likely cause some strife for people due to #37774

In the current state the IDE shows no errors and it's possible to work around/hide the "incorrect" CLI errors with a custom tsc wrapper.

If this bug is fixed then the IDE would show errors and there would be no way to silence them.

So they might best be solved together so that the IDE only shows these errors for "truly invalid" usecases (eg accessing a const enum from a node_module where the existence of preserveConstEnum can't be determined) and no errors are shown for "valid" usecases (eg accessing a const enum from a project reference)

[andrewbranch]

I think that this bug is basically expected behavior that falls out of the poor design or bug that is #37774. I want to try to address #37774 directly to close this.