fix(table): export menu works for plain-Python data without `pandas/polars/pyarrow` by kirangadhave · Pull Request #9246 · marimo-team/marimo

kirangadhave · 2026-04-17T17:56:15Z

When using python dict or list(dict) with mo.ui.table without any dataframe library installed, the Export button was hidden.

DefaultTableManager.supports_download() checked for dataframe libraries and returned False. We now always show the download button. We can support csv, json, md with stdlib in python. If user selects parquet, we show a toast for missing packages and an install button.

The MissingPackagePrompt is mode-aware. In run mode where users cannot install packages it shows a Parquet export isn't available in this notebook without an install button.

Notes
The DefaultTableManager always uses csv lib even if pandas/polars is installed. Exporting actual dataframe objects is not affected.
We suggest polars instead of pyarrow because we already have a polars code path which is well tested

Screen.Recording.2026-04-17.at.10.27.37.AM.mov

…lars/pyarrow

vercel · 2026-04-17T17:56:20Z

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Pull request overview

Fixes mo.ui.table export behavior when the table is backed by plain-Python data (dict / list[dict]) and no dataframe libraries are installed, by ensuring the Export UI is available and providing a structured “missing dependency” flow for Parquet.

Changes:

Remove dependency-gated download support for DefaultTableManager and implement CSV export via Python stdlib (csv).
Extend the download RPC contract to return structured error / missing_packages for unsupported formats (notably Parquet without deps), and surface this in the Export UI via a new mode-aware prompt.
Add/adjust backend and frontend tests covering the new behaviors.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
`marimo/_plugins/ui/_impl/tables/default_table.py`	Removes dep-based download gating; implements stdlib CSV export and CSV cell serialization helper.
`marimo/_plugins/ui/_impl/table.py`	Extends download response shape; adds Parquet missing-deps short-circuit for tables.
`frontend/src/components/data-table/schemas.ts`	Updates RPC schema typings/output to include `error` and `missing_packages`.
`frontend/src/components/data-table/export-actions.tsx`	Handles missing-package download responses by showing a toast with an install prompt + retry.
`frontend/src/components/datasources/missing-package-prompt.tsx`	New reusable mode-aware missing-package UI (hides install option in read mode).
`frontend/src/core/mode.ts`	Adds `useInstallAllowed()` helper based on current app mode.
`tests/_plugins/ui/_impl/test_table.py`	Adds backend test asserting Parquet-without-deps returns structured missing-packages response.
`tests/_plugins/ui/_impl/tables/test_default_table.py`	Adds/updates tests for `supports_download()` and CSV output for plain-Python default tables.
`frontend/src/components/datasources/__tests__/missing-package-prompt.test.tsx`	New tests validating prompt copy/button behavior in edit vs read mode.

mscolnick · 2026-04-17T19:02:58Z

+        if args.format == "parquet":
+            has_polars = DependencyManager.polars.has()
+            has_pandas = DependencyManager.pandas.has()
+            has_pyarrow = DependencyManager.pyarrow.has()


this may do more work than required (has() would import things). but its not a common path so don't need to optimize

github-actions · 2026-04-17T19:09:51Z

🚀 Development release published. You may be able to view the changes at https://marimo.app?v=0.23.2-dev50

#9246 moved DefaultTableManager.to_csv_str to the stdlib csv module, which emits column name "value" for single-column data. Previously the fallback went through pandas (via _as_table_manager), so a list of ints became a DataFrame with integer column 0. The test's expected_df still used {0: [1, 2, 3]}; update it to {"value": [1, 2, 3]} to match. The post-search assertion was already {"value": [2]}, so no change there.

Unblocks the test_be CI after #9305. Each of these five failures has an independent root cause — grouping them since the fixes are small and share the same goal. - **`test_download_as[df0]`** — the Parquet short-circuit in `_download_as` required `polars OR (pandas AND pyarrow)`, rejecting pyarrow-alone environments even though pyarrow can write Parquet natively. Relax to `polars OR pyarrow`. The `_parquet_without_libs_reports_missing_packages` and `_parquet_with_pandas_only_prompts_pyarrow` regression tests still pass. - **`test_get_data_url_no_deps`** — #9246 rewrote `DefaultTableManager.to_csv_str` to use the stdlib `csv` module, so `_to_chart_data_url` now returns CSV instead of falling through to JSON. Update the test expectation. - **`test_get_data_url_values`** — same #9246 change: stdlib CSV emits column name `"value"` for single-column data, where the old pandas fallback produced integer column `0`. Update the first `expected_df` to `{"value": [1, 2, 3]}`. (Landed as a separate commit after I found it on a broader sweep with the `test-optional` group.) - **`test_serve_static_allowed_files`** — `serve_static` returned `FileResponse` without checking existence, so Starlette raised `RuntimeError` at request time when the file was missing. CI copies `index.html` and `favicon.ico` into `_static/` but not `manifest.json`, which is how this surfaced. Add an `is_file()` guard that 404s. The test passed locally only because `_static/` doesn't exist on dev machines and `PathValidator` rejected upstream. - **`test_get_completion_options_bails_out_when_timeout_elapsed`** — #9247 switched the production code to `time.monotonic` but the test still mocked `time.time`, so the budget never expired and all completions got types set. Mock `time.monotonic`. ## Test plan - [x] Ran all four originally-failing tests; they pass. - [x] Ran the affected modules (`test_table.py`, `test_assets.py`, `test_complete.py`) with the `test` group — no new failures; pre-existing `test_index*` failures need a built `_static/` which CI provides. - [x] Ran the same modules with `test-optional` (pandas + polars + pyarrow + altair) — uncovered and fixed `test_get_data_url_values`. - [x] Confirmed the Parquet "missing packages" prompts still fire correctly under pandas-only and no-lib environments. - [ ] Let CI verify Linux/Windows.

…o-team#9306) Unblocks the test_be CI after marimo-team#9305. Each of these five failures has an independent root cause — grouping them since the fixes are small and share the same goal. - **`test_download_as[df0]`** — the Parquet short-circuit in `_download_as` required `polars OR (pandas AND pyarrow)`, rejecting pyarrow-alone environments even though pyarrow can write Parquet natively. Relax to `polars OR pyarrow`. The `_parquet_without_libs_reports_missing_packages` and `_parquet_with_pandas_only_prompts_pyarrow` regression tests still pass. - **`test_get_data_url_no_deps`** — marimo-team#9246 rewrote `DefaultTableManager.to_csv_str` to use the stdlib `csv` module, so `_to_chart_data_url` now returns CSV instead of falling through to JSON. Update the test expectation. - **`test_get_data_url_values`** — same marimo-team#9246 change: stdlib CSV emits column name `"value"` for single-column data, where the old pandas fallback produced integer column `0`. Update the first `expected_df` to `{"value": [1, 2, 3]}`. (Landed as a separate commit after I found it on a broader sweep with the `test-optional` group.) - **`test_serve_static_allowed_files`** — `serve_static` returned `FileResponse` without checking existence, so Starlette raised `RuntimeError` at request time when the file was missing. CI copies `index.html` and `favicon.ico` into `_static/` but not `manifest.json`, which is how this surfaced. Add an `is_file()` guard that 404s. The test passed locally only because `_static/` doesn't exist on dev machines and `PathValidator` rejected upstream. - **`test_get_completion_options_bails_out_when_timeout_elapsed`** — marimo-team#9247 switched the production code to `time.monotonic` but the test still mocked `time.time`, so the budget never expired and all completions got types set. Mock `time.monotonic`. ## Test plan - [x] Ran all four originally-failing tests; they pass. - [x] Ran the affected modules (`test_table.py`, `test_assets.py`, `test_complete.py`) with the `test` group — no new failures; pre-existing `test_index*` failures need a built `_static/` which CI provides. - [x] Ran the same modules with `test-optional` (pandas + polars + pyarrow + altair) — uncovered and fixed `test_get_data_url_values`. - [x] Confirmed the Parquet "missing packages" prompts still fire correctly under pandas-only and no-lib environments. - [ ] Let CI verify Linux/Windows.

kirangadhave added 2 commits April 16, 2026 18:15

fix(table): export menu works for plain-Python data without pandas/po…

64b3ea6

…lars/pyarrow

fix(table): mode-aware missing-packages prompt for Parquet export

08bc256

kirangadhave requested review from Light2Dark and mscolnick and removed request for Light2Dark April 17, 2026 17:56

[pre-commit.ci] auto fixes from pre-commit.com hooks

043473d

for more information, see https://pre-commit.ci

kirangadhave added the bug Something isn't working label Apr 17, 2026

vercel Bot deployed to Preview April 17, 2026 17:57 View deployment

kirangadhave requested a review from Light2Dark April 17, 2026 18:00

Light2Dark requested a review from Copilot April 17, 2026 18:02

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Comment thread marimo/_plugins/ui/_impl/tables/default_table.py

Comment thread marimo/_plugins/ui/_impl/table.py Outdated

fix(table): tighten Parquet dep check and handle None in CSV

4579540

kirangadhave force-pushed the kg/default-df-export-btn-bug branch from 21ea42e to 4579540 Compare April 17, 2026 18:47

vercel Bot deployed to Preview April 17, 2026 18:48 View deployment

mscolnick reviewed Apr 17, 2026

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mscolnick approved these changes Apr 17, 2026

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kirangadhave merged commit 0f934c1 into main Apr 17, 2026
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kirangadhave deleted the kg/default-df-export-btn-bug branch April 17, 2026 19:05

akshayka mentioned this pull request Apr 21, 2026

fix: unblock five test_be failures left after #9305 #9306

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fix(table): export menu works for plain-Python data without `pandas/polars/pyarrow`#9246

fix(table): export menu works for plain-Python data without `pandas/polars/pyarrow`#9246
kirangadhave merged 4 commits intomainfrom
kg/default-df-export-btn-bug

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