feat(table): locale-aware CSV and TSV exports by kirangadhave · Pull Request #10661 · marimo-team/marimo

kirangadhave · 2026-08-26T06:32:02Z

Summary

CSV and TSV table exports now use the resolved frontend locale for numeric decimal separators. File download and clipboard copy share one backend artifact.
JSON, Parquet, and Markdown stay locale-neutral. locale is optional so older clients keep today's comma/dot CSV. An explicit download_csv_separator still wins.
Comma-decimal locales (e.g. pt-BR) use ; as the default CSV field separator. No thousands grouping.

CSV and TSV downloads need the browser decimal separator on the wire. Keep locale optional so older clients can still send only format. Co-authored-by: Cursor <cursoragent@cursor.com>

CSV and TSV need a shared field and decimal separator policy so adapters can format numbers without rewriting completed text. Default-table exports stay locale-neutral unless a dialect is provided.

Pandas and Polars already wrap Narwhals, so locale decimal formatting belongs in one writer. Adapters only prepare index and nested columns.

vercel · 2026-08-26T06:32:09Z

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github-actions · 2026-08-26T06:32:18Z

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Copilot

Pull request overview

This PR adds locale-aware numeric formatting for CSV/TSV table exports by passing a browser-resolved locale (specifically the decimal separator) from the frontend to the backend export pipeline, while keeping JSON/Parquet/Markdown locale-neutral and preserving legacy behavior when locale is omitted.

Changes:

Introduces a shared “delimited dialect” model (field + decimal separators) and uses it for both file downloads and clipboard copy requests.
Updates table manager implementations (default/pandas/polars/narwhals) plus the narwhals CSV utility to support locale-specific decimal separators (no thousands grouping; semicolon CSV for comma-decimal locales by default).
Adds backend + frontend test coverage for locale resolution, dialect selection, and export output parity across CSV/TSV vs locale-neutral formats.

Reviewed changes

Copilot reviewed 27 out of 27 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
tests/_utils/test_narwhals_utils.py	Adds CSV export tests for comma and Unicode decimal separators.
tests/_plugins/ui/_impl/utils/test_dataframe_utils.py	Adds download-as tests covering pt-BR CSV/TSV behavior, legacy behavior, and locale-neutral JSON.
tests/_plugins/ui/_impl/test_table.py	Verifies `locale` is optional in args parsing and that table downloads honor locale for CSV/TSV only.
tests/_plugins/ui/_impl/tables/test_polars_table.py	Adds `to_delimited_str` tests for polars manager across decimal/exponent/non-finite/unicode cases.
tests/_plugins/ui/_impl/tables/test_pandas_table.py	Adds `to_delimited_str` tests for pandas manager across decimal/exponent/non-finite/unicode cases.
tests/_plugins/ui/_impl/tables/test_narwhals_table.py	New tests for narwhals table manager delimited exports and locale neutrality of CSV.
tests/_plugins/ui/_impl/tables/test_delimited.py	New tests for dialect resolution rules and locale validation.
tests/_plugins/ui/_impl/tables/test_default_table.py	Adds default table delimited export tests (no grouping, quoting rules, unicode decimal, neutrality).
tests/_plugins/ui/_impl/dataframes/test_dataframe.py	Adds dataframe UI element download tests ensuring locale-aware CSV/TSV and locale-neutral JSON/Parquet.
packages/openapi/src/api.ts	Regenerates/moves OpenAPI component type ordering (no functional change).
packages/openapi/api.yaml	Regenerates/moves OpenAPI component ordering (no functional change).
marimo/_utils/narwhals_utils.py	Extends `dataframe_to_csv` with optional dialect support and decimal separator formatting path.
marimo/_plugins/ui/_impl/utils/dataframe.py	Threads optional `locale` through `download_as` and unifies CSV/TSV export via delimited serialization.
marimo/_plugins/ui/_impl/tables/table_manager.py	Adds `to_delimited_str` default API to TableManager interface.
marimo/_plugins/ui/_impl/tables/polars_table.py	Routes delimited export through `dataframe_to_csv` with dialect and improves error handling for narwhals compute errors.
marimo/_plugins/ui/_impl/tables/pandas_table.py	Routes delimited export through narwhals CSV utility, including index-as-columns handling.
marimo/_plugins/ui/_impl/tables/narwhals_table.py	Implements `to_delimited_str` and updates CSV path to use dialect defaults.
marimo/_plugins/ui/_impl/tables/delimited.py	New module defining locale/dialect types, dialect resolution, and numeric formatting helpers.
marimo/_plugins/ui/_impl/tables/default_table.py	Implements delimited export with numeric decimal replacement using resolved dialect.
marimo/_plugins/ui/_impl/table.py	Extends download args with optional locale and forwards it into export pipeline.
marimo/_plugins/ui/_impl/dataframes/dataframe.py	Forwards optional locale into dataframe export pipeline.
frontend/src/components/data-table/schemas.ts	Extends RPC schema/types to accept optional locale.
frontend/src/components/data-table/export-locale.ts	New helper to resolve decimal separator from `Intl.NumberFormat(...).formatToParts`.
frontend/src/components/data-table/export-actions.tsx	Uses `useLocale()` to attach locale to CSV/TSV download/copy requests and factors request-building helpers.
frontend/src/components/data-table/tests/export-locale.test.ts	Adds tests for locale resolution and schema acceptance of optional locale.
frontend/src/components/data-table/tests/export-actions.test.tsx	Adds tests ensuring parity between download and clipboard requests (locale included only for CSV/TSV).
frontend/plugins.openapi.yaml	Updates generated frontend OpenAPI schema to include optional locale for download_as inputs.

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cubic-dev-ai

All reported issues were addressed

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github-actions · 2026-08-26T06:37:58Z

Coverage Report for ./frontend

Status	Category	Percentage	Covered / Total
🔵	Lines	56.19%	20972 / 37317
🔵	Statements	56.11%	21339 / 38027
🔵	Functions	49.07%	4703 / 9583
🔵	Branches	49.53%	10782 / 21765

File Coverage

File	Stmts	Branches	Functions	Lines	Uncovered Lines
Changed Files
frontend/src/components/data-table/export-actions.tsx	51.16%	35.71%	52.38%	51.19%	124, 170-177, 181-192, 204-207, 216, 221, 230-238, 242, 247-282, 333-369
frontend/src/components/data-table/export-locale.ts	87.5%	85.71%	100%	87.5%	24-26
frontend/src/components/data-table/schemas.ts	100%	100%	100%	100%

Generated in workflow #20840 for commit ef964c5 by the Vitest Coverage Report Action

Locale-aware delimited serialization bypassed Polars normalization, changed pandas index headers and Windows line endings, and rejected empty configured separators. Keep locale policy in the table layer while moving serialization primitives below it. Return structured locale validation errors without hiding unrelated export failures.

cubic-dev-ai

All reported issues were addressed across 16 files (changes from recent commits).

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Structured export errors must stop file and clipboard actions before empty URLs reach the browser. Polars also needs a safe fallback for nested containers that cannot use its native string cast. Preserve the fast scalar path, serialize complex nested cells as JSON, and expose numeric narrowing through a TypeGuard.

cubic-dev-ai

All reported issues were addressed across 6 files (changes from recent commits).

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Download and clipboard rows exposed the same accessible name, which let the download error regression test pass through either action. Give each action a distinct name so assistive technology and tests can select it reliably. Pandas-native CSV output also follows the platform line separator. Compare the compatibility tests with pandas output so the Windows job does not assume LF.

Light2Dark

5.6 Sol on Codex

I found one pandas export regression to address.

The updated frontend sends a locale for every CSV and TSV request, including en-US. That means pandas exports now use PandasTableManager.to_delimited_str. For a dataframe with an unnamed, non-default index, this method calls with_index_as_columns(), which gives the index a synthetic name.

Before this PR, pandas produces:

,value
10,1.5

With this PR, the same export produces:

Index0,value
10,1.5

Unnamed MultiIndex levels similarly become Index0, Index1, and so on. This changes the exported column schema even though the feature should only change field and decimal separators.

Light2Dark

kirangadhave and others added 5 commits August 25, 2026 16:17

feat(frontend): resolve locale for table export requests

7a22005

CSV and TSV downloads need the browser decimal separator on the wire. Keep locale optional so older clients can still send only format. Co-authored-by: Cursor <cursoragent@cursor.com>

feat(table): add locale-aware delimited export dialect

7277673

CSV and TSV need a shared field and decimal separator policy so adapters can format numbers without rewriting completed text. Default-table exports stay locale-neutral unless a dialect is provided.

feat(table): format delimited exports through Narwhals

6f15d6e

Pandas and Polars already wrap Narwhals, so locale decimal formatting belongs in one writer. Adapters only prepare index and nested columns.

feat(table): plumb locale through download_as handlers

5dfee48

feat(frontend): send locale with CSV and TSV table exports

e58029b

Copilot AI lite review requested due to automatic review settings August 26, 2026 06:32

github-actions Bot added the bash-focus Area to focus on during release bug bash label Aug 26, 2026

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Copilot started reviewing on behalf of kirangadhave August 26, 2026 06:32 View session

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Light2Dark mentioned this pull request Aug 27, 2026

perf(table): make localized Polars exports native-speed #10674

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perf(table): make localized Polars exports native-speed (#10674)

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kirangadhave marked this pull request as draft August 27, 2026 18:15

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