component-refactoring

# Langflow Component Refactoring Skill Refactor high-complexity React components in the Langflow frontend codebase with the patterns and workflow below. > **Complexity Threshold**: Components with complexity > 50 (measured manually by counting conditionals, nesting levels, and lines) should be refactored before testing. ## Quick Reference ### Commands (run from `src/frontend/`) ```bash cd src/frontend # Lint with Biome npm run lint # Type checking npm run type-check # Run tests npm test ``` ### Manual Complexity Assessment Since Langflow does not have automated complexity analysis tools, assess components manually: 1. **Count conditionals**: Each `if/else`, `switch/case`, ternary, `&&`/`||` chain adds +1. 2. **Count nesting levels**: Each level of nesting within conditionals or loops adds +1. 3. **Count total lines**: Target < 300 lines per component file. 4. **Count state hooks**: More than 5 `useState` calls suggests hook extraction. 5. **Count effects**: More than 3 `useEffect` calls suggests effect consolidation. ### Complexity Score Interpretation | Score | Level | Action | |-------|-------|--------| | 0-25 | Simple | Ready for testing | | 26-50 | Medium | Consider minor refactoring | | 51-75 | Complex | **Refactor before testing** | | 76-100 | Very Complex | **Must refactor** | ## Core Refactoring Patterns ### Pattern 1: Extract Custom Hooks **When**: Component has complex state management, multiple `useState`/`useEffect`, or business logic mixed with UI. **Langflow Convention**: Place hooks in a `hooks/` subdirectory or alongside the component as `use-<feature>.ts`. Langflow uses kebab-case filenames with `use-` prefix. ```typescript // Before: Complex state logic in component const FlowPage: FC = () => { const [nodes, setNodes] = useState<Node[]>([]) const [edges, setEdges] = useState<Edge[]>([]) const [buildStatus, setBuildStatus] = useState<BuildStatus>(BuildStatus.IDLE) // 50+ lines of state management logic... return <div>...</div> } // After: Extract to custom hook // hooks/use-flow-state.ts export const useFlowState = (flowId: string) => { const [nodes, setNodes] = useState<Node[]>([]) const [edges, setEdges] = useState<Edge[]>([]) const [buildStatus, setBuildStatus] = useState<BuildStatus>(BuildStatus.IDLE) // Related state management logic here return { nodes, setNodes, edges, setEdges, buildStatus, setBuildStatus } } // Component becomes cleaner const FlowPage: FC = () => { const { nodes, setNodes, edges, setEdges } = useFlowState(flowId) return <div>...</div> } ``` **Langflow Examples**: - `src/frontend/src/hooks/use-add-component.ts` - `src/frontend/src/hooks/use-unsaved-changes.ts` - `src/frontend/src/hooks/use-refresh-model-inputs.ts` ### Pattern 2: Extract Sub-Components **When**: Single component has multiple UI sections, conditional rendering blocks, or repeated patterns. **Langflow Convention**: Place sub-components in subdirectories or as separate files in the same directory. UI primitives go in `components/ui/`, domain components in `components/core/`, reusable components in `components/common/`. ```typescript // Before: Monolithic JSX with multiple sections const GenericNode = () => { return ( <div> {/* 100 lines of header UI */} {/* 100 lines of parameter fields */} {/* 100 lines of output handles */} </div> ) } // After: Split into focused components // CustomNodes/GenericNode/ // generic-node.tsx (orchestration only — kebab-case, descriptive name) // components/ // node-header.tsx // node-parameters.tsx // node-outputs.tsx const GenericNode = () => { return ( <div> <NodeHeader nodeData={data} /> <NodeParameters fields={fields} /> <NodeOutputs outputs={outputs} /> </div> ) } ``` **Langflow Examples**: - `src/frontend/src/CustomNodes/GenericNode/components/` - `src/frontend/src/components/core/` - `src/frontend/src/components/ui/` ### Pattern 3: Simplify Conditional Logic **When**: Deep nesting (> 3 levels), complex ternaries, or multiple `if/else` chains. ```typescript // Before: Deeply nested conditionals const getFieldComponent = (field: InputFieldType) => { if (field.type === "str") { if (field.multiline) { return <TextAreaComponent /> } else if (field.password) { return <PasswordInput /> } else if (field.options?.length) { return <Dropdown options={field.options} /> } else { return <InputComponent /> } } else if (field.type === "int") { return <IntComponent /> } else if (field.type === "float") { return <FloatComponent /> } return null } // After: Use lookup tables + early returns const FIELD_COMPONENT_MAP: Record<string, FC<FieldProps>> = { int: IntComponent, float: FloatComponent, bool: ToggleComponent, code: CodeAreaComponent, } const STR_VARIANT_MAP: Record<string, FC<FieldProps>> = { multiline: TextAreaComponent, password: PasswordInput, options: Dropdown, } const getFieldComponent = (field: InputFieldType) => { if (field.type !== "str") { const Component = FIELD_COMPONENT_MAP[field.type] return Component ? <Component {...field} /> : null } const variant = field.multiline ? "multiline" : field.password ? "password" : field.options?.length ? "options" : "default" const Component = STR_VARIANT_MAP[variant] ?? InputComponent return <Component {...field} /> } ``` ### Pattern 4: Extract API/Data Logic **When**: Component directly handles API calls, data transformation, or complex async operations. **Langflow Convention**: - This skill is for component decomposition, not query/mutation design. - When refactoring data fetching, use `frontend-query-mutation` for query patterns, `UseRequestProcessor`, cache invalidation, and mutation error handling. - Do not create thin passthrough `useQuery` wrappers during refactoring; only extract a custom hook when it truly orchestrates multiple queries/mutations or shared derived state. - API hooks live in `controllers/API/queries/{domain}/`. **Langflow Examples**: - `src/frontend/src/controllers/API/queries/flows/use-post-add-flow.ts` - `src/frontend/src/controllers/API/queries/variables/use-get-global-variables.ts` - `src/frontend/src/controllers/API/queries/folders/use-get-folders.ts` ### Pattern 5: Extract Modal/Dialog Management **When**: Component manages multiple modals with complex open/close states. **Langflow Convention**: Modals should be extracted with their state management. ```typescript // Before: Multiple modal states in component const FlowToolbar = () => { const [showExportModal, setShowExportModal] = useState(false) const [showShareModal, setShowShareModal] = useState(false) const [showDeleteConfirm, setShowDeleteConfirm] = useState(false) const [showApiModal, setShowApiModal] = useState(false) // 5+ more modal states... } // After: Extract to modal management hook type ModalType = "export" | "share" | "delete" | "api" | null const useFlowToolbarModals = () => { const [activeModal, setActiveModal] = useState<ModalType>(null) const openModal = useCallback((type: ModalType) => setActiveModal(type), []) const closeModal = useCallback(() => setActiveModal(null), []) return { activeModal, openModal, closeModal, isOpen: (type: ModalType) => activeModal === type, } } ``` ### Pattern 6: Extract Form Logic **When**: Complex form validation, submission handling, or field transformation. **Langflow Convention**: Extract form state and validation into hooks. ```typescript // Extract form validation and submission const useFlowSettingsForm = (initialValues: FlowSettings) => { const [values, setValues] = useState(initialValues) const [errors, setErrors] = useState<Record<string, string>>({}) const validate = useCallback(() => { const newErrors: Record<string, string> = {} if (!values.name?.trim()) newErrors.name = "Name is required" if (values.endpoint_name && !/^[a-z0-9-]+$/.test(values.endpoint_name)) { newErrors.endpoint_name = "Must be lowercase alphanumeric with hyphens" } setErrors(newErrors) return Object.keys(newErrors).length === 0 }, [values]) const handleChange = useCallback((field: string, value: any) => { setValues((prev) => ({ ...prev, [field]: value })) }, []) return { values, errors, validate, handleChange } } ``` ## Langflow-Specific Refactoring Guidelines ### 1. Zustand Store Selectors **When**: Component reads many values from a Zustand store, causing unnecessary re-renders. ```typescript // Before: Selecting too many values const Component = () => { const flowStore = useFlowStore() // Component re-renders on ANY store change } // After: Use individual selectors const Component = () => { const nodes = useFlowStore((state) => state.nodes) const edges = useFlowStore((state) => state.edges) // Component only re-renders when nodes or edges change } ``` **Langflow Reference**: All stores in `src/frontend/src/stores/` follow this selector pattern. ### 2. Custom Node Components **When**: Refactoring flow node components (`CustomNodes/GenericNode/`). **Conventions**: - Keep node logic in custom hooks - Extract parameter rendering to separate components - Use the existing `components/` subdirectory for sub-components ``` CustomNodes/GenericNode/ generic-node.tsx # Node registration and main render (kebab-case, NOT index.tsx) components/ handle-render.tsx # Handle rendering node-description.tsx # Node description display node-input-field.tsx # Input field rendering node-name.tsx # Node name display node-output-field.tsx # Output field rendering node-status.tsx # Build status display ``` ### 3. Flow Canvas Components **When**: Refactoring components related to the flow editor canvas. **Conventions**: - `@xyflow/react` v12 is the canvas library - Keep canvas event handlers separate from UI rendering - Use `useFlowStore` for flow state management - Use `useFlowsManagerStore` for multi-flow management ### 4. API Query Hook Components **When**: Refactoring components that consume API data. **Conventions**: - Use existing query hooks from `controllers/API/queries/` - Access `UseRequestProcessor` for new queries/mutations - Use query key arrays like `["useGetGlobalVariables"]` for cache management - Cache invalidation belongs in mutation `onSettled` callbacks ## Refactoring Workflow ### Step 1: Assess Complexity Manually count: - Total conditionals (if/else, switch, ternary, &&/||) - Maximum nesting depth - Total lines of code - Number of useState/useEffect hooks - Number of distinct UI sections ### Step 2: Plan Create a refactoring plan based on detected features: | Detected Feature | Refactoring Action | |------------------|-------------------| | 5+ `useState` hooks with related state | Extract custom hook | | API calls in component body | Extract to query hook | | 3+ event handlers with logic | Extract event handlers to hook | | 300+ lines | Split into sub-components | | Deep conditional nesting (>3) | Simplify conditional logic | | Multiple modal states | Extract modal management | ### Step 3: Execute Incrementally 1. **Extract one piece at a time** 2. **Run lint, type-check, and tests after each extraction** 3. **Verify functionality before next step** ``` For each extraction: 1. Extract code 2. Run: npm run lint 3. Run: npm run type-check 4. Run: npm test 5. Test functionality manually 6. PASS? -> Next extraction FAIL? -> Fix before continuing ``` ### Step 4: Verify After refactoring, re-assess complexity manually: - Target complexity < 50 - Target line count < 300 - Target max nesting depth <= 3 - Target max function length < 30 lines ## Common Mistakes to Avoid ### Over-Engineering ```typescript // Too many tiny hooks const useButtonText = () => useState("Click") const useButtonDisabled = () => useState(false) const useButtonLoading = () => useState(false) // Cohesive hook with related state const useButtonState = () => { const [text, setText] = useState("Click") const [disabled, setDisabled] = useState(false) const [loading, setLoading] = useState(false) return { text, setText, disabled, setDisabled, loading, setLoading } } ``` ### Breaking Existing Patterns