dualfroz
aa4f462b2e
Buffer::nth() resolved the requested position by adding it to the first row key and indexing the rows array by that computed key. That assumes contiguous keys, but Buffer::delete() removes rows with unset() without reindexing, leaving gaps. After a deletion nth() therefore returned the wrong record (or an empty array for a valid position, or a record for an out-of-range position). Resolve the position against the record order with array_values() so nth() matches getRecords() and ResultSet::nth().
95 lines
3.2 KiB
Markdown
95 lines
3.2 KiB
Markdown
# fix: make Buffer::nth() positional so it stays correct after deletions
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## Problem
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`Buffer::nth()` (and `Buffer::nthAsObject()`) return the wrong record once a
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record has been deleted from the buffer. `nth()` is a positional accessor - the
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same contract implemented by `ResultSet::nth()` via
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`new LimitIterator($iterator, $nth, 1)` - so `nth($n)` must return the `$n`-th
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record in iteration order, consistent with `getRecords()`.
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```php
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$buffer = new League\Csv\Buffer(['id', 'name']);
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$buffer->insert(['1', 'a'], ['2', 'b'], ['3', 'c'], ['4', 'd'], ['5', 'e']);
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$buffer->delete(fn (array $row) => $row['id'] === '2');
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// getRecords() correctly yields a, c, d, e
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// but:
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$buffer->nth(1); // [] (expected ['id' => '3', 'name' => 'c'])
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$buffer->nth(4); // ['5', 'e'] (expected [] - only 4 records remain)
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```
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## Root cause
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`src/Buffer.php`, `nthRow()`:
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```php
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$offset = $first + $nth;
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if (!array_key_exists($offset, $this->rows)) {
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return [];
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}
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return $this->rows[$nth + $first];
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```
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The lookup adds `$nth` to the first row key and indexes `$this->rows` by that
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computed key. That only works while the row keys are contiguous.
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`Buffer::delete()` removes rows with `unset($this->rows[$offset])` without
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reindexing, so after any deletion the keys contain gaps and the positional index
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`$nth` no longer maps to key `$first + $nth`. As a result `nth()` skips the
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deleted offset, and can also return a record for an index that is out of range.
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## The fix
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Resolve `$nth` against the record order instead of the row keys:
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```php
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private function nthRow(int $nth, string $method): array
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{
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-1 < $nth || throw InvalidArgument::dueToInvalidRecordOffset($nth, $method);
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return array_values($this->rows)[$nth] ?? [];
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}
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```
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`array_values()` collapses the gaps, so `$nth` addresses the record by its
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position in iteration order, matching `getRecords()` and `ResultSet::nth()`.
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`array_values` is already imported by the class.
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## Test
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Added `BufferTest::it_returns_records_by_positional_offset_after_a_middle_record_is_deleted`,
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which inserts five records, deletes a middle one, and asserts that
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`nth(0..3)` return the four remaining records in order and that `nth(4)` returns
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`[]`.
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## Gate
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```
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composer install --ignore-platform-req=ext-xdebug
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vendor/bin/phpunit --no-coverage
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```
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The full run reports 6 pre-existing errors, all
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`PDOException: could not find driver` from the SQLite3/PDO-backed tests
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(`RdbmsResultTest` and the `sqlite3`/`pdo` cases in `BufferTest`); these are
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environmental (the `sqlite3` / `pdo_sqlite` extensions are not installed) and are
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present unchanged on a clean checkout. Excluding those environment-dependent
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cases the suite is green:
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```
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vendor/bin/phpunit --no-coverage --filter '/^(?!.*(sqlite3|pdo)).*$/i'
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```
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Result: exit code `0` - `OK, but some tests were skipped! Tests: 1006,
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Assertions: 1990, Skipped: 3` (the 3 skips are pre-existing).
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Counterfactual: reverting `nthRow()` to the key-arithmetic version makes the new
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test fail - `nth(1)` returns `[]` instead of `['id' => '3', 'name' => 'c']`.
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## Flags for the account owner
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The SQLite3/PDO tests are not annotated with a required-extension attribute, so
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they error (rather than skip) when the drivers are missing. That is unrelated to
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this change and was left untouched.
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