get_cwd() variable substitution

[Copilot]

get_cwd() gained support for nine VS Code file-related variables but had no tests. Adds 17 focused unit tests covering every variable, composite patterns, multi-variable strings, and no-document fallback behaviour.

Changes

• src/test/python_tests/test_get_cwd.py — new self-contained test file; includes a _setup_mocks() helper that stubs out the bundled LSP dependencies (pygls, lsprotocol, lsp_jsonrpc, lsp_utils) at module level so lsp_server can be imported without the full VS Code extension environment. No conftest.py needed.

# Tests cover each variable individually...
def test_file_dirname_resolved():
    settings = _make_settings(cwd="${fileDirname}")
    assert lsp_server.get_cwd(settings, DOC) == "/home/user/myproject/src"

# ...composite patterns...
def test_composite_pattern_resolved():
    settings = _make_settings(cwd="${fileDirname}/subdir")
    assert lsp_server.get_cwd(settings, DOC) == "/home/user/myproject/src/subdir"

# ...and fallback when no document is available
def test_file_variable_no_document_falls_back_to_workspace():
    for token in ["${file}", "${fileDirname}", "${fileWorkspaceFolder}", ...]:
        settings = _make_settings(cwd=token + "/extra")
        assert lsp_server.get_cwd(settings, None) == WORKSPACE

Original prompt

Context

PR #260 added a configurable cwd setting with variable substitution. The TypeScript client (src/common/settings.ts resolveVariables()) pre-resolves ${workspaceFolder}, ${userHome}, ${cwd}, and ${workspaceFolder:name} before sending settings to the Python server. The Python server's get_cwd() in bundled/tool/lsp_server.py then handles document-dependent variables that can't be resolved at settings-load time.

However, as @rchiodo pointed out in #260 (comment), the current get_cwd() only resolves ${fileDirname}. There are more file-related variables from VS Code's variables reference (https://code.visualstudio.com/docs/reference/variables-reference) that should also be resolved server-side since they depend on the current document.

Required Change

Only modify bundled/tool/lsp_server.py — expand the get_cwd() function (currently at line 292) to resolve additional file-related VS Code variables using a substitution-map approach.

The current implementation on main at line 292-306 is:

def get_cwd(settings: dict, document: Optional[workspace.Document]) -> str:
    """Returns the working directory for running the tool.

    Resolves ``${fileDirname}`` to the directory of the current document.
    If no document is available, falls back to the workspace root.

    Examples of supported patterns: ``${fileDirname}``, ``${fileDirname}/subdir``.
    """
    cwd = settings.get("cwd", settings["workspaceFS"])
    if "${fileDirname}" in cwd:
        if document and document.path:
            cwd = cwd.replace("${fileDirname}", os.path.dirname(document.path))
        else:
            cwd = settings["workspaceFS"]
    return cwd

Replace it with a version that builds a substitution map of all document-dependent variables and applies them. Here's what the new function should look like:

def get_cwd(settings: dict, document: Optional[workspace.Document]) -> str:
    """Returns the working directory for running the tool.

    Resolves the following VS Code file-related variable substitutions when
    a document is available:

    - ``${file}`` – absolute path of the current document.
    - ``${fileBasename}`` – file name with extension (e.g. ``foo.py``).
    - ``${fileBasenameNoExtension}`` – file name without extension (e.g. ``foo``).
    - ``${fileExtname}`` – file extension including the dot (e.g. ``.py``).
    - ``${fileDirname}`` – directory containing the current document.
    - ``${fileDirnameBasename}`` – name of the directory containing the document.
    - ``${relativeFile}`` – document path relative to the workspace root.
    - ``${relativeFileDirname}`` – document directory relative to the workspace root.
    - ``${fileWorkspaceFolder}`` – workspace root folder for the document.

    Variables that do not depend on the document (``${workspaceFolder}``,
    ``${userHome}``, ``${cwd}``) are pre-resolved by the TypeScript client.

    If no document is available and the value contains any unresolvable
    file-variable, the workspace root is returned as a fallback.

    See https://code.visualstudio.com/docs/reference/variables-reference
    """
    cwd = settings.get("cwd", settings["workspaceFS"])

    workspace_fs = settings["workspaceFS"]

    if document and document.path:
        file_path = document.path
        file_dir = os.path.dirname(file_path)
        file_basename = os.path.basename(file_path)
        file_stem, file_ext = os.path.splitext(file_basename)

        substitutions = {
            "${file}": file_path,
            "${fileBasename}": file_basename,
            "${fileBasenameNoExtension}": file_stem,
            "${fileExtname}": file_ext,
            "${fileDirname}": file_dir,
            "${fileDirnameBasename}": os.path.basename(file_dir),
            "${relativeFile}": os.path.relpath(file_path, workspace_fs),
            "${relativeFileDirname}": os.path.relpath(file_dir, workspace_fs),
            "${fileWorkspaceFolder}": workspace_fs,
        }

        for token, value in substitutions.items():
            cwd = cwd.replace(token, value)
    else:
        # Without a document we cannot resolve file-related variables.
        # Fall back to workspace root if any remain.
        if "${file" in cwd or "${relativeFile" in cwd:
            cwd = workspace_fs

    return cwd

Do NOT modify settings.ts, package.json, or any other file — only bundled/tool/lsp_server.py.

This pull request was created from Copilot chat.

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[edvilme]

Originated from #260 (comment) (@rchiodo)

[rchiodo]

Should there be a unit test for all of these?

[edvilme]

@copilot Generate unit tests to check that the replacements actually work. Remember this repo is a bootstrapper, so try to keep it simple and straight to the point.

[Copilot]

Added 17 unit tests in src/test/python_tests/test_get_cwd.py (commit 0e48096). A conftest.py stubs out the heavy LSP dependencies so lsp_server can be imported in a plain pytest run. The tests cover every variable (${file}, ${fileBasename}, ${fileBasenameNoExtension}, ${fileExtname}, ${fileDirname}, ${fileDirnameBasename}, ${relativeFile}, ${relativeFileDirname}, ${fileWorkspaceFolder}), composite patterns, fallback-to-workspace-root when no document is available, and unchanged passthrough for plain paths.