feat(file_browser): restore selection_mode='all' and accept list form

[kirangadhave]

Summary

• Restore the selection_mode="all" string on mo.ui.file_browser (regressed in fix: handle cloudpath client #4130).
• Also accept a list/tuple form, e.g. selection_mode=["file", "directory"].
• Internally normalized to a frozenset of selectable kinds; the wire format stays a single string ("file" | "directory" | "all"), so the frontend (which already handles "all") is unchanged.
• Default remains "file"; no behavior change for existing callers.

Closes #9402

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Project	Deployment	Actions	Updated (UTC)
marimo-docs	Ready	Preview, Comment	May 20, 2026 7:17pm

[kirangadhave]

@cubic-dev-ai

[cubic-dev-ai]

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[cubic-dev-ai]

No issues found across 3 files

Architecture diagram

sequenceDiagram
    participant User as User (Python cell)
    participant FileBrowser as mo.ui.file_browser __init__
    participant Normalizer as _normalize_selection_mode()
    participant WireFormat as Wire format builder
    participant Frontend as Frontend component
    participant DirLister as _list_directory()
    participant FileSystem as Filesystem

    Note over User,FileSystem: Initialization flow

    User->>FileBrowser: file_browser(selection_mode="all")
    FileBrowser->>Normalizer: NEW: normalize "all"
    Normalizer-->>FileBrowser: frozenset({"file","directory"})

    User->>FileBrowser: file_browser(selection_mode=["file","directory"])
    FileBrowser->>Normalizer: NEW: normalize list
    Normalizer-->>FileBrowser: frozenset({"file","directory"})

    User->>FileBrowser: file_browser(selection_mode="file") (unchanged)
    FileBrowser->>Normalizer: normalize "file"
    Normalizer-->>FileBrowser: frozenset({"file"})

    Note over FileBrowser,WireFormat: Derive wire format for frontend

    alt selection_mode == {"file","directory"} (i.e. "all")
        FileBrowser->>WireFormat: wire = "all"
    else single kind selected
        FileBrowser->>WireFormat: wire = single element from frozenset
    end
    WireFormat-->>FileBrowser: "all" | "file" | "directory"
    FileBrowser-->>User: UIElement created (unchanged frontend contract)

    Note over Frontend,FileSystem: Directory listing flow (CHANGED: filtering logic)

    Frontend->>DirLister: list_directory(path)
    DirLister->>FileSystem: read directory entries
    FileSystem-->>DirLister: list of entries (files + directories)

    loop each entry
        alt entry is directory
            DirLister->>DirLister: Always included (for navigation)
        else entry is file
            alt "file" in self._selection_mode
                DirLister->>DirLister: Include (subject to filetypes)
            else "file" not in self._selection_mode
                DirLister->>DirLister: NEW: Skip file (was only directory mode previously)
            end
        end
    end

    DirLister-->>Frontend: filtered file list

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[Copilot]

Pull request overview

Restores mo.ui.file_browser(selection_mode="all") support (regressed previously) and extends selection_mode to also accept a list/tuple form, while keeping the frontend wire format limited to "file" | "directory" | "all".

Changes:

• Added internal normalization of selection_mode to a frozenset of selectable kinds, supporting "all" and list/tuple inputs.
• Updated directory listing behavior to hide files when file selection is disabled, while always showing directories for navigation.
• Added/updated tests and an example demonstrating selection_mode="all".

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
marimo/_plugins/ui/_impl/file_browser.py	Adds selection mode normalization + wire-format mapping and updates listing behavior accordingly.
tests/_plugins/ui/_impl/test_file_browser.py	Updates existing assertions and adds coverage for normalization, "all" mode, and list/tuple inputs.
examples/ui/file_browser.py	Demonstrates a file browser instance using selection_mode="all".

[Light2Dark]

doesn't this mean ["file", "directory"] is the same as "all". What's the reason to have both list & str support?

[kirangadhave]

yeah it's same as all. If we add something like symlinks or some other type in future, we can pick and choose with this pattern. all will always be all supported types. just a bit of over-engineering for future proofing.

[Light2Dark]

got it, im usually not keen on over-eng, but leaving it to you.