use `export function x(...)` instead of `export const x`

[aeschli]

See https://github.com/microsoft/vscode/wiki/Coding-Guidelines

Discussion in slack: https://vscodeteam.slack.com/archives/C03ERNTC03X/p1746179392005339

[legomushroom]

Yeah I saw this new rule in the Slack. It is now a rule, so I have to comply 😃

Because this rule is so new, there are a lot of the same patterns across the codebase. Should it be a project-wide adoption effort, or you already creating items for each author?

My quick search yields around ~100 results in ~80 files if only top level lambda function definitions are considered. If all the definitions are taken into account (i.e. lambda function defined in another function or method) there are around 2458 results in 965 files 🙈

The search attributes I've used:

• ^const \w+ = \( (regex)
• files to include: *.ts
• files to exclude: **/*prompt*/**/*.ts, *.test.ts, build/**, extensions/**, scripts/**,.eslint-plugin-local

Couple of examples:

https://github.com/microsoft/vscode/blob/main/src/vs/base/browser/ui/hover/hoverDelegateFactory.ts#L9
https://github.com/microsoft/vscode/blob/main/src/vs/base/browser/ui/list/listWidget.ts#L1227
https://github.com/microsoft/vscode/blob/main/src/vs/base/browser/ui/progressbar/progressAccessibilitySignal.ts#L10
https://github.com/microsoft/vscode/blob/main/src/vs/base/common/async.ts#L333
https://github.com/microsoft/vscode/blob/main/src/vs/base/common/async.ts#L348
https://github.com/microsoft/vscode/blob/main/src/vs/base/common/path.ts#L1135
https://github.com/microsoft/vscode/blob/main/src/vs/base/common/diff/diff.ts#L1153
https://github.com/microsoft/vscode/blob/main/src/vs/base/test/common/snapshot.ts#L18
https://github.com/microsoft/vscode/blob/main/src/vs/editor/browser/viewParts/minimap/minimapPreBaked.ts#L27
https://github.com/microsoft/vscode/blob/main/src/vs/editor/browser/viewParts/viewLines/viewLine.ts#L24

[legomushroom]

Overall would love to learn more for your preference of this pattern vs another one. Is it mostly a stylistic preference or there are some functional reasons behind it? @bpasero please chime in too!

My choice for the lambda functions by default is rooted into the functional aspects they have, but I totally see cons and pros for each. What's on your list?

[bpasero]

Here I would suggest to find a ESLint rule and do a project wide adoption to export function so that code is consistent and easy to read. The disadvantage of export const foo = function is that its not immediately clear what gets exported, at least when I read over it.

[jrieken]

cc @connor4312 - you seem to be in export-const-function-expression camp and might wanna migrate some of yours, e.g this or this

[jrieken]

This search (#248387 (comment)) turns up usages of export-const which are IMO legit, esp things like export const foo = IIFE->function which is something we do to create a function for a context-dependent variant. For instance generateUuid is such a case - it either uses the platform uuid-function or uses its own variant. The use of export-IIFE means the probing for the platform support happens only once and not on each invocation. We should not change these