`swift package plugin --list` ignores `swift.buildPath`

### Description When `swift.buildPath` is configured, `BuildFlags.withSwiftSDKFlags` adds the necessary parameters to the `package` command. This doesn't work today for the `plugin` subcommand since #1996 added an early exit. However, while #1996 silenced the issue, I believe we can actually address it. When operating on the `package` command, `BuildFlags.withSwiftSDKFlags` puts the flags _after_ the subcommand, which work for `diagnose` and `dump-symbol-graph` (maybe because they don't have further subcommands with positional arguments), but not for `plugin`: ``` ❯ swift package plugin --scratch-path /tmp/scratch --list error: Unknown option '--scratch-path' ``` The issue is that `--scratch-path` is a parameter for the `package` command, and therefore should be added _before_ the subcommand: ``` # This works because `--scratch-path` is passed to `package`, not `plugin` ❯ swift package --scratch-path /tmp/scratch plugin --list Fetching https://github.com/apple/swift-collections.git from cache [...] ``` ### Fixing the issue I believe the fix should be as simple as changing where we add the build path flags in [BuildFlags.ts](https://github.com/swiftlang/vscode-swift/blob/main/src/toolchain/BuildFlags.ts#L50-L51), which would then allow us to remove the special flag ```typescript case "package": { // Build-path flags belong on the parent `package` command, before any // subcommand, otherwise SwiftPM's argument parser rejects them when // the subcommand itself has further subcommands or positional args // (e.g. `swift package plugin --list`). const command = args.splice(0, 1).concat(this.buildPathFlags()); // command = ["package", "--scratch-path", "<path>"], args = [subcommand, ...] switch (args[0]) { case "dump-symbol-graph": case "diagnose-api-breaking-changes": case "resolve": return [...command, ...this.swiftpmSDKFlags(), ...args]; default: return command.concat(args); } } ``` ### Steps to reproduce Notes: I'm reproducing using [build-your-own-redis](https://github.com/codecrafters-io/build-your-own-redis/), specifically within the [`starter_templates/swift/code` folder](https://github.com/codecrafters-io/build-your-own-redis/tree/main/starter_templates/swift/code). But this likely reproduces with any Swift PM projects, especially if they have external dependencies. 1. Checkout [build-your-own-redis](https://github.com/codecrafters-io/build-your-own-redis/) 2. Create `.vscode/settings.json` to set `swift.buildPath` somewhere in `/tmp`. For example: `{"swift.buildPath": "/tmp/codecrafters-swift-scratch/"}` 3. Make sure no `.build` folder exists ``` fd -u '^\.build$' --exec rm {} ``` 4. Open the workspace with VS code at the root 5. Open `starter_templates/swift/code/Sources/main.swift` 6. Wait a minute or so, during which you ideally should see the Swift plugin doing a few things (indexing, etc.) 7. At the root of the workspace, look for `.build` folders: ``` fd -u '^\.build$' ``` You will see a `.build` that was created: ``` ❯ fd -u '^\.build$' starter_templates/swift/code/.build/ ``` ### Proof of root cause I noticed the issue while using the `course-sdk` tool, where files were often missing or having permission issues. I realised this was because `course-sdk` generates new Swift files, and with VS code open in the workspace, `course-sdk`'s use of SwiftPM and listing + copying files created some races with VS code's Swift PM reindexing. I therefore looked to move all build files to `/tmp` using `swift.buildPath`, and while a lot ended up in the `/tmp` folder, I still had race issues because `.build` kept being created. I used [Mac Monitor](https://github.com/Brandon7CC/mac-monitor) to find out who/what was creating the folder, and found this call chain: ``` launchd └── Code └── Code Helper (Plugin) └── swift-package plugin --list # cwd = starter_templates/swift/code └── CREATE starter_templates/swift/code/.build/ ``` I then came to GitHub, looked for issues & PRs with `--scratch-path`, and found #1996. ### Expected behavior `/tmp/codecrafters-swift-scratch` exists, and no `.build` folder is found in the workspace. ### Extension version 2.16.4 ### Swift & OS version Swift: 6.3 macOS: 26.4.1