composer.json discovery fails in VS Code remote

issueで参照されているcomposer.jsonの検索箇所をsrc/options.mjsから確認し、次にsrc/parser.mjsがPHPファイルのコンテキストをどのように渡しているかを追跡します。CLIとVS Codeのリモート環境の違いを再現し、src/a.phpのフォーマット時にworkspaceのルートにあるcomposer.jsonを検出できることを、既存のCLIの動作を維持したまま検証します。

In my (admittedly specific) use case the plugin is unable to find composer.json, which is plainly present in the root of the workspace.

Environment

Running VS Code with a devcontainer in Rancher Desktop. Prettier plugin is running inside the container.
prettier and @prettier/plugin-php are installed locally inside node_modules and the VS Code plugin uses the local installation.

Settings:
"phpVersion": "composer"

Filesystem layout:

• /workspaces/myproject/
  • composer.json
  • .prettierrc
  • node_modules/
  • src/
    • a.php

Result

When run on src/a.php through VS Code, the plugin fails.

["ERROR" - 9:22:26 AM] Error formatting document.
["ERROR" - 9:22:26 AM] Could not determine PHP version from composer; Could not find composer.json
Error: Could not determine PHP version from composer; Could not find composer.json
    at resolvePhpVersion (file:///workspaces/myproject/node_modules/@prettier/plugin-php/src/options.mjs:95:13)
    at Object.parse (file:///workspaces/myproject/node_modules/@prettier/plugin-php/src/parser.mjs:11:3)
    at parse5 (file:///workspaces/myproject/node_modules/prettier/index.mjs:16731:24)
    at async coreFormat (file:///workspaces/myproject/node_modules/prettier/index.mjs:17287:25)
    at async formatWithCursor (file:///workspaces/myproject/node_modules/prettier/index.mjs:17504:14)
    at async Module.format2 (file:///workspaces/myproject/node_modules/prettier/index.mjs:19051:25)

When doing the same thing through the CLI, not the VS Code plugin, everything works as expected.

Cause

A little bit of digging turns up the root cause here: https://github.com/prettier/plugin-php/blob/0c883a49850281077218007322f6149f853b2015/src/options.mjs#L23

In my environment, prettier is run in this directory: /vscode/vscode-server/bin/linux-x64/360a4e4fd251bfce169a4ddf857c7d25d1ad40da
The recursive search for composer.json upwards from process.cwd() fails.

I don't feel qualified to suggest a solution but maybe search from the target file's location upwards, instead of the process' working dir?