OverrideClickResolver — Specs

Line coverage: OverrideClickResolver.swift 93% · refreshed 2026-05-27 by /coverage-explore

Summary

In Settings, each shortcut can override the global Appearance values (style / size / theme / shortcut-style). A segmented control shows either the global value (no override) or the override value. OverrideClickResolver.decide is the pure kernel for "what should a click on that segment do": given the clicked index, whether an override is currently set, the stored override value, the current global index, and a valueAtIndex encoder, it returns .skip (no change) or .write(value:) (set/update the override).

The key invariant it encodes (the rules the user stated): an override's set/unset state and its value are independent. Clicking the currently-displayed value never changes state; clicking a different value writes/updates the override; and the only way to unset an override is the link button (never modeled as a click here).

Behavior & edge cases

• Displayed value is derived from hasOverride + globalIndex, not from UserDefaults. This matters because the registered default for an override key can differ from the global — comparing against UserDefaults (the old bug) wrote/skipped incorrectly.
• A .write re-encodes the new index via valueAtIndex (the persisted string isn't assumed to equal the index).
• A malformed stored override (non-Int string) is treated as "displayed = -1", so a click still writes (corrupt defaults don't silently turn every click into a no-op).
• nil stored value with no override falls back to the global as the displayed value.

Test scenarios

Mirrors OverrideClickResolverTests.swift 1:1.

Rule 1 — clicking the displayed value is a no-op

• testNoOpWhenClickingDisplayedGlobal — override unset, click the displayed global → .skip.
• testNoOpWhenClickingDisplayedOverride — override set, click the displayed override value → .skip.
• testOverrideStaysSetWhenItsValueMatchesGlobal — override set to a value that coincides with the global; clicking it stays .skip (set-state survives; only the link button unsets).
• testNoOpWhenRegisteredDefaultDiffersFromGlobal — displayed = global even when the registered default differs → .skip (regression: don't compare against UserDefaults).

Rule 2 — clicking a different value writes the override

• testWriteOverrideOnClickAwayFromGlobal — override unset, click a different value → .write.
• testWriteOverrideOnClickAwayFromExistingOverride — override set, click a different value → .write (still set, new value).
• testWritesOverrideWhenClickValueEqualsRegisteredDefault — new value equals the registered default but differs from global → .write (regression: previously skipped).
• testWriteOverrideEvenWhenNewValueMatchesGlobal — new value coincidentally equals the global but differs from the current override → .write (stays set).

Encoding & defensive handling

• testValueAtIndexEncoderIsHonored — the persisted string comes from valueAtIndex, not the raw index.
• testStoredOverrideMalformedFallsThroughToWrite — corrupt stored value (non-Int) → treated as displayed -1 → .write.
• testNilStoredOverrideWithMatchingGlobalIsSkip — nil stored value, override unset, click the global → .skip.
• testHasOverrideTrueWithNilStoredFallsThroughToWrite — inconsistent state (override marked SET but stored value is nil) → treated as displayed -1 → .write (defensive: don't silently no-op).