Vue 3 debugging and error handling for runtime issues, warnings, async failures, and hydration bugs. For development best practices and common gotchas, use vue-best-practices.
Reactivity
- Tracing unexpected re-renders and state updates → See reactivity-debugging-hooks
- Ref values not updating due to missing.value access → See ref-value-access
- State stops updating after destructuring reactive objects → See reactive-destructuring
- Refs inside arrays, Maps, or Sets not unwrapping → See refs-in-collections-need-value
- Nested refs rendering as [object Object] in templates → See template-ref-unwrapping-top-level
- Reactive proxy identity comparisons always return false → See reactivity-proxy-identity-hazard
- Third-party instances breaking when proxied → See reactivity-markraw-for-non-reactive
- Watchers only firing once per tick unexpectedly → See reactivity-same-tick-batching
Computed
- Computed getter triggers mutations or requests unexpectedly → See computed-no-side-effects
- Mutating computed values causes changes to disappear → See computed-return-value-readonly
- Computed value never updates after conditional logic → See computed-conditional-dependencies
- Sorting or reversing arrays breaks original state → See computed-array-mutation
- Passing parameters to computed properties fails → See computed-no-parameters
Watchers
- Async operations overwriting with stale data → See watch-async-cleanup
- Creating watchers inside async callbacks → See watch-async-creation-memory-leak
- Watcher never triggers for reactive object properties → See watch-reactive-property-getter
- Async watchEffect misses dependencies after await → See watcheffect-async-dependency-tracking
- DOM reads are stale inside watcher callbacks → See watch-flush-timing
- Deep watchers report identical old/new values → See watch-deep-same-object-reference
- watchEffect runs before template refs update → See watcheffect-flush-post-for-refs
Components
- Child component throws "component not found" error → See local-components-not-in-descendants
- Click listener doesn't fire on custom component → See click-events-on-components
- Parent can't access child ref data in script setup → See component-ref-requires-defineexpose
- HTML template parsing breaks Vue component syntax → See in-dom-template-parsing-caveats
- Wrong component renders due to naming collisions → See component-naming-conflicts
- Parent styles don't apply to multi-root component → See multi-root-component-class-attrs
Props & Emits
- Variables referenced in defineProps cause errors → See prop-defineprops-scope-limitation
- Component emits undeclared event causing warnings → See declare-emits-for-documentation
- defineEmits used inside function or conditional → See defineEmits-must-be-top-level
- defineEmits has both type and runtime arguments → See defineEmits-no-runtime-and-type-mixed
- Native event listeners not responding to clicks → See native-event-collision-with-emits
- Component event fires twice when clicking → See undeclared-emits-double-firing
Templates
- Getting template compilation errors with statements → See template-expressions-restrictions
- "Cannot read property of undefined" runtime errors → See v-if-null-check-order
- Dynamic directive arguments not working properly → See dynamic-argument-constraints
- v-else elements rendering unconditionally always → See v-else-must-follow-v-if
- Mixing v-if with v-for causes precedence bugs and migration breakage → See no-v-if-with-v-for
- Template function calls mutating state cause unpredictable re-render bugs → See template-functions-no-side-effects
- Child components in loops showing undefined data → See v-for-component-props
- Array order changing after sorting or reversing → See v-for-computed-reverse-sort
- List items disappearing or swapping state unexpectedly → See v-for-key-attribute
- Getting off-by-one errors with range iteration → See v-for-range-starts-at-one
- v-show or v-else not working on template elements → See v-show-template-limitation
Template Refs
- Ref becomes null when element is conditionally hidden → See template-ref-null-with-v-if
- Ref array indices don't match data array in loops → See template-ref-v-for-order
- Refactoring template ref names breaks silently in code → See use-template-ref-vue35
Forms & v-model
- Initial form values not showing when using v-model → See v-model-ignores-html-attributes
- Textarea content changes not updating the ref → See textarea-no-interpolation
- iOS users cannot select dropdown first option → See select-initial-value-ios-bug
- Parent and child components have different values → See define-model-default-value-sync
- Object property changes not syncing to parent → See definemodel-object-mutation-no-emit
- Real-time search/validation broken for Chinese/Japanese input → See v-model-ime-composition
- Number input returns empty string instead of zero → See v-model-number-modifier-behavior
- Custom checkbox values not submitted in forms → See checkbox-true-false-value-form-submission
Events & Modifiers
- Chaining multiple event modifiers produces unexpected results → See event-modifier-order-matters
- Keyboard shortcuts don't fire with system modifier keys → See keyup-modifier-timing
- Keyboard shortcuts fire with unintended modifier combinations → See exact-modifier-for-precise-shortcuts
- Combining passive and prevent modifiers breaks event behavior → See no-passive-with-prevent
Lifecycle
- Memory leaks from unremoved event listeners → See cleanup-side-effects
- DOM access fails before component mounts → See lifecycle-dom-access-timing
- DOM reads return stale values after state changes → See dom-update-timing-nexttick
- SSR rendering differs from client hydration → See lifecycle-ssr-awareness
- Lifecycle hooks registered asynchronously never run → See lifecycle-hooks-synchronous-registration
Slots
- Accessing child component data in slot content returns undefined values → See slot-render-scope-parent-only
- Mixing named and scoped slots together causes compilation errors → See slot-named-scoped-explicit-default
- Using v-slot on native HTML elements causes compilation errors → See slot-v-slot-on-components-or-templates-only
- Unexpected content placement from implicit default slot behavior → See slot-implicit-default-content
- Scoped slot props missing expected name property → See slot-name-reserved-prop
- Wrapper components breaking child slot functionality → See slot-forwarding-to-child-components
Provide/Inject
- Calling provide after async operations fails silently → See provide-inject-synchronous-setup
- Tracing where provided values come from → See provide-inject-debugging-challenges
- Injected values not updating when provider changes → See provide-inject-reactivity-not-automatic
- Multiple components share same default object → See provide-inject-default-value-factory
Attrs
- Both internal and fallthrough event handlers execute → See attrs-event-listener-merging
- Explicit attributes overwritten by fallthrough values → See fallthrough-attrs-overwrite-vue3
- Attributes applying to wrong element in wrappers → See inheritattrs-false-for-wrapper-components
Composables
- Composable called outside setup context or asynchronously → See composable-call-location-restrictions
- Composable reactive dependency not updating when input changes → See composable-tovalue-inside-watcheffect
- Composable mutates external state unexpectedly → See composable-avoid-hidden-side-effects
- Destructuring composable returns breaks reactivity unexpectedly → See composable-naming-return-pattern
Composition API
- Lifecycle hooks failing silently after async operations → See composition-api-script-setup-async-context
- Parent component refs unable to access exposed properties → See define-expose-before-await
- Functional-programming patterns break expected Vue reactivity behavior → See composition-api-not-functional-programming
- React Hook mental model causes incorrect Composition API usage → See composition-api-vs-react-hooks-differences
Animation
- Animations fail to trigger when DOM nodes are reused → See animation-key-for-rerender
- TransitionGroup list updates feel laggy under load → See animation-transitiongroup-performance
TypeScript
- Mutable prop defaults leak state between component instances → See ts-withdefaults-mutable-factory-function
- reactive() generic typing causes ref unwrapping mismatches → See ts-reactive-no-generic-argument
- Template refs throw null access errors before mount or after v-if unmount → See ts-template-ref-null-handling
- Optional boolean props behave as false instead of undefined → See ts-defineprops-boolean-default-false
- Imported defineProps types fail with unresolvable or complex type references → See ts-defineprops-imported-types-limitations
- Untyped DOM event handlers fail under strict TypeScript settings → See ts-event-handler-explicit-typing
- Dynamic component refs trigger reactive component warnings → See ts-shallowref-for-dynamic-components
- Union-typed template expressions fail type checks without narrowing → See ts-template-type-casting
Async Components
- Route components misconfigured with defineAsyncComponent lazy loading → See async-component-vue-router
- Network failures or timeouts loading components → See async-component-error-handling
- Template refs undefined after component reactivation → See async-component-keepalive-ref-issue
Render Functions
- Render function output stays static after state changes → See rendering-render-function-return-from-setup
- Reused vnode instances render incorrectly → See render-function-vnodes-must-be-unique
- String component names render as HTML elements → See rendering-resolve-component-for-string-names
- Accessing vnode internals breaks on Vue updates → See render-function-avoid-internal-vnode-properties
- Vue 2 render function patterns crash in Vue 3 → See rendering-render-function-h-import-vue3
- Slot content not rendering from h() → See rendering-render-function-slots-as-functions
KeepAlive
- Child components mount twice with nested Vue Router routes → See keepalive-router-nested-double-mount
- Memory grows when combining KeepAlive with Transition animations → See keepalive-transition-memory-leak
Transitions
- JavaScript transition hooks hang without done callback → See transition-js-hooks-done-callback
- Move animations fail on inline list elements → See transition-group-flip-inline-elements
- List items jump instead of smoothly animating → See transition-group-move-animation-position-absolute
- Vue 2 to Vue 3 TransitionGroup wrapper changes break layout → See transition-group-no-default-wrapper-vue3
- Nested transitions cut off before finishing → See transition-nested-duration
- Scoped styles stop working in reusable transition wrappers → See transition-reusable-scoped-style
- RouterView transitions animate unexpectedly on first render → See transition-router-view-appear
- Mixing CSS transitions and animations causes timing issues → See transition-type-when-mixed
- Cleanup hooks missed during rapid transition swaps → See transition-unmount-hook-timing
Teleport
- Teleport target element not found in DOM → See teleport-target-must-exist
- Teleported content breaks SSR hydration → See teleport-ssr-hydration
- Scoped styles not applying to teleported content → See teleport-scoped-styles-limitation
Suspense
- Need to handle async errors from Suspense components → See suspense-no-builtin-error-handling
- Using Suspense with server-side rendering → See suspense-ssr-hydration-issues
- Async component loading/error UI ignored under Suspense → See async-component-suspense-control
SSR
- HTML differs between server and client renders → See ssr-hydration-mismatch-causes
- User state leaks between requests from shared singleton stores → See state-ssr-cross-request-pollution
- Browser-only APIs crash server rendering in universal code paths → See ssr-platform-specific-apis
Performance
- List children re-render unnecessarily because parent passes unstable props → See perf-props-stability-update-optimization
- Computed objects retrigger effects despite equivalent values → See perf-computed-object-stability
SFC (Single File Components)
- Trying to use named exports from component script blocks → See sfc-named-exports-forbidden
- Variables not updating in template after changes → See sfc-script-setup-reactivity
- Scoped styles not applying to child component elements → See sfc-scoped-css-child-component-styling
- Scoped styles not applying to dynamic v-html content → See sfc-scoped-css-dynamic-content
- Scoped styles not applying to slot content → See sfc-scoped-css-slot-content
- Tailwind classes missing when built dynamically → See tailwind-dynamic-class-generation
- Recursive components not rendering due to name conflicts → See self-referencing-component-name
Plugins
- Debugging why global properties cause naming conflicts → See plugin-global-properties-sparingly
- Plugin not working or inject returns undefined → See plugin-install-before-mount
- Plugin global properties are unavailable in setup-based components → See plugin-prefer-provide-inject-over-global-properties
- Plugin type augmentation mistakes break ComponentCustomProperties typing → See plugin-typescript-type-augmentation
App Configuration
- App configuration methods not working after mount call → See configure-app-before-mount
- Chaining app config off mount() fails because mount returns component instance → See mount-return-value
- require.context-based component auto-registration fails in Vite → See dynamic-component-registration-vite