Return -1 from SQLite String.IndexOf(value, startIndex) when the valu…

[ilkertskn]

…e is not found

• The translation computed (instr(substr(...)) - 1) + startIndex, which yields startIndex - 1 instead of -1 when instr returns 0 (the value is not found), so IndexOf produced a wrong non-negative result
• Wrap the result in a CASE that returns -1 when instr is 0, matching String.IndexOf
• Add a test for the not-found case and update the affected SQL baselines

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        Summary of the changes
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        Fixes #bugnumber

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[ilkertskn]

@dotnet-policy-service agree

[Copilot]

Pull request overview

Fixes SQLite translation of string.IndexOf(value, startIndex) so that it correctly returns -1 when the searched value isn’t found (SQLite instr() returns 0, which previously caused the expression to yield startIndex - 1).

Changes:

• Update SQLite IndexOf(..., startIndex) translation to wrap instr(substr(...)) in a CASE returning -1 when instr() returns 0.
• Update existing SQL baselines for IndexOf starting-position tests to reflect the new CASE translation.
• Add a new functional test covering the “not found => -1” case for IndexOf with a starting position.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
test/EFCore.Sqlite.FunctionalTests/Query/Translations/StringTranslationsSqliteTest.cs	Updates SQL baselines for starting-position IndexOf and adds a new test asserting -1 when not found.
src/EFCore.Sqlite.Core/Query/Internal/Translators/SqliteStringMethodTranslator.cs	Fixes the SQLite translation for IndexOf(value, startIndex) by guarding the instr() result with a CASE.