Don't transform empty CSV table that was never created#736
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insert_upsert_implementation always tries to call transform() after the insert when --detect-types is set, but for an empty CSV (header row only, no data rows) insert_all is a no-op and the table is never created. transform() then asserts table.exists() and crashes. Guard the transform call with table.exists(). Added a regression test that fails on main and passes here. Same guard applied to the analogous multi-file path further down. Closes simonw#702 Signed-off-by: Charlie Tonneslan <cst0520@gmail.com>
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Closes #702.
When a CSV file is header-only, `insert_all` is a no-op so the table never gets created, but the `--detect-types` path still calls `transform(types=tracker.types)` afterwards and `transform` asserts `table.exists()`. Result is the `AssertionError: Cannot transform a table that doesn't exist yet` traceback from the issue.
Gate the `transform` call on `table.exists()` so the empty case is a clean no-op. Applied the same guard to the analogous loop further down in `memory`-style multi-file insertion. Added a regression test that fails on main and passes here.
📚 Documentation preview 📚: https://sqlite-utils--736.org.readthedocs.build/en/736/