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Author SHA1 Message Date
Jorge Cabiedes Acosta
2d26ba5483 [compiler] Change ValidateNoDerivedComputationsInEffect logic to track prop and local state derived values variables 2025-09-23 11:25:43 -07:00
Jorge Cabiedes Acosta
f989af23f9 [compiler] ValidateNoDerivedComputationsInEffects test cases
Summary:
This creates the test cases we expect this first iteration of calculate in render to catch

Test Plan:
Test cases:
2025-09-23 11:25:43 -07:00
29 changed files with 1262 additions and 148 deletions

View File

@@ -5,21 +5,31 @@
* LICENSE file in the root directory of this source tree.
*/
import {CompilerError, SourceLocation} from '..';
import {CompilerError, Effect} from '..';
import {ErrorCategory} from '../CompilerError';
import {
ArrayExpression,
BlockId,
FunctionExpression,
HIRFunction,
IdentifierId,
isSetStateType,
isUseEffectHookType,
Place,
CallExpression,
Instruction,
isUseStateType,
} from '../HIR';
import {
eachInstructionValueOperand,
eachTerminalOperand,
} from '../HIR/visitors';
import {eachInstructionLValue, eachInstructionOperand} from '../HIR/visitors';
import {isMutable} from '../ReactiveScopes/InferReactiveScopeVariables';
import {assertExhaustive} from '../Utils/utils';
type TypeOfValue = 'ignored' | 'fromProps' | 'fromState' | 'fromPropsAndState';
type DerivationMetadata = {
typeOfValue: TypeOfValue;
place: Place;
sourcesIds: Set<IdentifierId>;
};
/**
* Validates that useEffect is not used for derived computations which could/should
@@ -45,102 +55,226 @@ import {
* ```
*/
export function validateNoDerivedComputationsInEffects(fn: HIRFunction): void {
const candidateDependencies: Map<IdentifierId, ArrayExpression> = new Map();
const functions: Map<IdentifierId, FunctionExpression> = new Map();
const locals: Map<IdentifierId, IdentifierId> = new Map();
const derivationCache: Map<IdentifierId, DerivationMetadata> = new Map();
if (fn.fnType === 'Hook') {
for (const param of fn.params) {
if (param.kind === 'Identifier') {
derivationCache.set(param.identifier.id, {
place: param,
sourcesIds: new Set([param.identifier.id]),
typeOfValue: 'fromProps',
});
}
}
} else if (fn.fnType === 'Component') {
const props = fn.params[0];
if (props != null && props.kind === 'Identifier') {
derivationCache.set(props.identifier.id, {
place: props,
sourcesIds: new Set([props.identifier.id]),
typeOfValue: 'fromProps',
});
}
}
const errors = new CompilerError();
for (const block of fn.body.blocks.values()) {
for (const instr of block.instructions) {
const {lvalue, value} = instr;
if (value.kind === 'LoadLocal') {
locals.set(lvalue.identifier.id, value.place.identifier.id);
} else if (value.kind === 'ArrayExpression') {
candidateDependencies.set(lvalue.identifier.id, value);
} else if (value.kind === 'FunctionExpression') {
functions.set(lvalue.identifier.id, value);
} else if (
value.kind === 'CallExpression' ||
value.kind === 'MethodCall'
) {
const callee =
value.kind === 'CallExpression' ? value.callee : value.property;
if (
isUseEffectHookType(callee.identifier) &&
value.args.length === 2 &&
value.args[0].kind === 'Identifier' &&
value.args[1].kind === 'Identifier'
for (const phi of block.phis) {
let typeOfValue: TypeOfValue = 'ignored';
let sourcesIds: Set<IdentifierId> = new Set();
for (const operand of phi.operands.values()) {
const operandMetadata = derivationCache.get(operand.identifier.id);
if (operandMetadata === undefined) {
continue;
}
typeOfValue = joinValue(typeOfValue, operandMetadata.typeOfValue);
sourcesIds.add(operand.identifier.id);
}
if (typeOfValue !== 'ignored') {
addDerivationEntry(phi.place, sourcesIds, typeOfValue, derivationCache);
}
}
for (const i of block.instructions) {
function recordInstructiorDerivations(instr: Instruction): void {
let typeOfValue: TypeOfValue = 'ignored';
const sources: Set<IdentifierId> = new Set();
const {lvalue, value} = instr;
if (value.kind === 'FunctionExpression') {
functions.set(lvalue.identifier.id, value);
for (const [, block] of value.loweredFunc.func.body.blocks) {
for (const instr of block.instructions) {
recordInstructiorDerivations(instr);
}
}
} else if (
value.kind === 'CallExpression' ||
value.kind === 'MethodCall'
) {
const effectFunction = functions.get(value.args[0].identifier.id);
const deps = candidateDependencies.get(value.args[1].identifier.id);
const callee =
value.kind === 'CallExpression' ? value.callee : value.property;
if (
effectFunction != null &&
deps != null &&
deps.elements.length !== 0 &&
deps.elements.every(element => element.kind === 'Identifier')
isUseEffectHookType(callee.identifier) &&
value.args.length === 2 &&
value.args[0].kind === 'Identifier' &&
value.args[1].kind === 'Identifier'
) {
const dependencies: Array<IdentifierId> = deps.elements.map(dep => {
CompilerError.invariant(dep.kind === 'Identifier', {
reason: `Dependency is checked as a place above`,
const effectFunction = functions.get(value.args[0].identifier.id);
if (effectFunction != null) {
validateEffect(
effectFunction.loweredFunc.func,
errors,
derivationCache,
);
}
} else if (isUseStateType(lvalue.identifier)) {
const stateValueSource = value.args[0];
if (stateValueSource.kind === 'Identifier') {
sources.add(stateValueSource.identifier.id);
}
typeOfValue = joinValue(typeOfValue, 'fromState');
}
}
for (const operand of eachInstructionOperand(instr)) {
const operandMetadata = derivationCache.get(operand.identifier.id);
if (operandMetadata === undefined) {
continue;
}
typeOfValue = joinValue(typeOfValue, operandMetadata.typeOfValue);
for (const id of operandMetadata.sourcesIds) {
sources.add(id);
}
}
if (typeOfValue === 'ignored') {
return;
}
for (const lvalue of eachInstructionLValue(instr)) {
addDerivationEntry(lvalue, sources, typeOfValue, derivationCache);
}
for (const operand of eachInstructionOperand(instr)) {
switch (operand.effect) {
case Effect.Capture:
case Effect.Store:
case Effect.ConditionallyMutate:
case Effect.ConditionallyMutateIterator:
case Effect.Mutate: {
if (isMutable(instr, operand)) {
addDerivationEntry(
operand,
sources,
typeOfValue,
derivationCache,
);
}
break;
}
case Effect.Freeze:
case Effect.Read: {
// no-op
break;
}
case Effect.Unknown: {
CompilerError.invariant(false, {
reason: 'Unexpected unknown effect',
description: null,
details: [
{
kind: 'error',
loc: value.loc,
message: 'this is checked as a place above',
loc: operand.loc,
message: 'Unexpected unknown effect',
},
],
});
return locals.get(dep.identifier.id) ?? dep.identifier.id;
});
validateEffect(
effectFunction.loweredFunc.func,
dependencies,
errors,
);
}
default: {
assertExhaustive(
operand.effect,
`Unexpected effect kind \`${operand.effect}\``,
);
}
}
}
}
recordInstructiorDerivations(i);
}
}
if (errors.hasAnyErrors()) {
throw errors;
}
}
function joinValue(
lvalueType: TypeOfValue,
valueType: TypeOfValue,
): TypeOfValue {
if (lvalueType === 'ignored') return valueType;
if (valueType === 'ignored') return lvalueType;
if (lvalueType === valueType) return lvalueType;
return 'fromPropsAndState';
}
function addDerivationEntry(
derivedVar: Place,
sourcesIds: Set<IdentifierId>,
typeOfValue: TypeOfValue,
derivationCache: Map<IdentifierId, DerivationMetadata>,
): void {
let newValue: DerivationMetadata = {
place: derivedVar,
sourcesIds: new Set(),
typeOfValue: typeOfValue ?? 'ignored',
};
if (sourcesIds !== undefined) {
for (const id of sourcesIds) {
const sourcePlace = derivationCache.get(id)?.place;
if (sourcePlace === undefined) {
continue;
}
/*
* If the identifier of the source is a promoted identifier, then
* we should set the target as the source.
*/
if (
sourcePlace.identifier.name === null ||
sourcePlace.identifier.name?.kind === 'promoted'
) {
newValue.sourcesIds.add(derivedVar.identifier.id);
} else {
newValue.sourcesIds.add(sourcePlace.identifier.id);
}
}
}
derivationCache.set(derivedVar.identifier.id, newValue);
}
function validateEffect(
effectFunction: HIRFunction,
effectDeps: Array<IdentifierId>,
errors: CompilerError,
derivationCache: Map<IdentifierId, DerivationMetadata>,
): void {
for (const operand of effectFunction.context) {
if (isSetStateType(operand.identifier)) {
continue;
} else if (effectDeps.find(dep => dep === operand.identifier.id) != null) {
continue;
} else {
// Captured something other than the effect dep or setState
return;
}
}
for (const dep of effectDeps) {
if (
effectFunction.context.find(operand => operand.identifier.id === dep) ==
null
) {
// effect dep wasn't actually used in the function
return;
}
}
const seenBlocks: Set<BlockId> = new Set();
const values: Map<IdentifierId, Array<IdentifierId>> = new Map();
for (const dep of effectDeps) {
values.set(dep, [dep]);
}
const setStateLocations: Array<SourceLocation> = [];
const effectDerivedSetStateCalls: Array<{
value: CallExpression;
sourceIds: Set<IdentifierId>;
}> = [];
for (const block of effectFunction.body.blocks.values()) {
for (const pred of block.preds) {
if (!seenBlocks.has(pred)) {
@@ -148,90 +282,36 @@ function validateEffect(
return;
}
}
for (const phi of block.phis) {
const aggregateDeps: Set<IdentifierId> = new Set();
for (const operand of phi.operands.values()) {
const deps = values.get(operand.identifier.id);
if (deps != null) {
for (const dep of deps) {
aggregateDeps.add(dep);
}
}
}
if (aggregateDeps.size !== 0) {
values.set(phi.place.identifier.id, Array.from(aggregateDeps));
}
}
for (const instr of block.instructions) {
switch (instr.value.kind) {
case 'Primitive':
case 'JSXText':
case 'LoadGlobal': {
break;
}
case 'LoadLocal': {
const deps = values.get(instr.value.place.identifier.id);
if (deps != null) {
values.set(instr.lvalue.identifier.id, deps);
}
break;
}
case 'ComputedLoad':
case 'PropertyLoad':
case 'BinaryExpression':
case 'TemplateLiteral':
case 'CallExpression':
case 'MethodCall': {
const aggregateDeps: Set<IdentifierId> = new Set();
for (const operand of eachInstructionValueOperand(instr.value)) {
const deps = values.get(operand.identifier.id);
if (deps != null) {
for (const dep of deps) {
aggregateDeps.add(dep);
}
}
}
if (aggregateDeps.size !== 0) {
values.set(instr.lvalue.identifier.id, Array.from(aggregateDeps));
}
if (
instr.value.kind === 'CallExpression' &&
isSetStateType(instr.value.callee.identifier) &&
instr.value.args.length === 1 &&
instr.value.args[0].kind === 'Identifier'
) {
const deps = values.get(instr.value.args[0].identifier.id);
if (deps != null && new Set(deps).size === effectDeps.length) {
setStateLocations.push(instr.value.callee.loc);
} else {
// doesn't depend on any deps
return;
}
}
break;
for (const instr of block.instructions) {
if (
instr.value.kind === 'CallExpression' &&
isSetStateType(instr.value.callee.identifier) &&
instr.value.args.length === 1 &&
instr.value.args[0].kind === 'Identifier'
) {
const argMetadata = derivationCache.get(
instr.value.args[0].identifier.id,
);
if (argMetadata !== undefined) {
effectDerivedSetStateCalls.push({
value: instr.value,
sourceIds: argMetadata.sourcesIds,
});
}
default: {
return;
}
}
}
for (const operand of eachTerminalOperand(block.terminal)) {
if (values.has(operand.identifier.id)) {
//
return;
}
}
seenBlocks.add(block.id);
}
for (const loc of setStateLocations) {
for (const derivedSetStateCall of effectDerivedSetStateCalls) {
errors.push({
category: ErrorCategory.EffectDerivationsOfState,
reason:
'Values derived from props and state should be calculated during render, not in an effect. (https://react.dev/learn/you-might-not-need-an-effect#updating-state-based-on-props-or-state)',
description: null,
loc,
loc: derivedSetStateCall.value.loc,
suggestions: null,
});
}

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@@ -0,0 +1,88 @@
## Input
```javascript
// @validateNoDerivedComputationsInEffects
import {useEffect, useState} from 'react';
function Component({initialName}) {
const [name, setName] = useState('');
useEffect(() => {
setName(initialName);
}, [initialName]);
return (
<div>
// 🟡 If the is also called outside of the effect, it's still wrong but
should be solved by hoisting state
<input value={name} onChange={e => setName(e.target.value)} />
</div>
);
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{initialName: 'John'}],
};
```
## Code
```javascript
import { c as _c } from "react/compiler-runtime"; // @validateNoDerivedComputationsInEffects
import { useEffect, useState } from "react";
function Component(t0) {
const $ = _c(6);
const { initialName } = t0;
const [name, setName] = useState("");
let t1;
let t2;
if ($[0] !== initialName) {
t1 = () => {
setName(initialName);
};
t2 = [initialName];
$[0] = initialName;
$[1] = t1;
$[2] = t2;
} else {
t1 = $[1];
t2 = $[2];
}
useEffect(t1, t2);
let t3;
if ($[3] === Symbol.for("react.memo_cache_sentinel")) {
t3 = (e) => setName(e.target.value);
$[3] = t3;
} else {
t3 = $[3];
}
let t4;
if ($[4] !== name) {
t4 = (
<div>
// 🟡 If the is also called outside of the effect, it's still wrong but
should be solved by hoisting state
<input value={name} onChange={t3} />
</div>
);
$[4] = name;
$[5] = t4;
} else {
t4 = $[5];
}
return t4;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{ initialName: "John" }],
};
```
### Eval output
(kind: ok) <div>// 🟡 If the is also called outside of the effect, it's still wrong but should be solved by hoisting state<input value="John"></div>

View File

@@ -0,0 +1,23 @@
// @validateNoDerivedComputationsInEffects
import {useEffect, useState} from 'react';
function Component({initialName}) {
const [name, setName] = useState('');
useEffect(() => {
setName(initialName);
}, [initialName]);
return (
<div>
// 🟡 If the is also called outside of the effect, it's still wrong but
should be solved by hoisting state
<input value={name} onChange={e => setName(e.target.value)} />
</div>
);
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{initialName: 'John'}],
};

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@@ -0,0 +1,67 @@
## Input
```javascript
// @validateNoDerivedComputationsInEffects
import {useEffect, useState} from 'react';
function Component({propValue}) {
const [value, setValue] = useState(null);
useEffect(() => {
setValue(propValue);
}, [propValue]);
return <MockComponent setter={setValue} />;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{propValue: 'test'}],
};
```
## Code
```javascript
import { c as _c } from "react/compiler-runtime"; // @validateNoDerivedComputationsInEffects
import { useEffect, useState } from "react";
function Component(t0) {
const $ = _c(4);
const { propValue } = t0;
const [, setValue] = useState(null);
let t1;
let t2;
if ($[0] !== propValue) {
t1 = () => {
setValue(propValue);
};
t2 = [propValue];
$[0] = propValue;
$[1] = t1;
$[2] = t2;
} else {
t1 = $[1];
t2 = $[2];
}
useEffect(t1, t2);
let t3;
if ($[3] === Symbol.for("react.memo_cache_sentinel")) {
t3 = <MockComponent setter={setValue} />;
$[3] = t3;
} else {
t3 = $[3];
}
return t3;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{ propValue: "test" }],
};
```
### Eval output
(kind: exception) MockComponent is not defined

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@@ -0,0 +1,16 @@
// @validateNoDerivedComputationsInEffects
import {useEffect, useState} from 'react';
function Component({propValue}) {
const [value, setValue] = useState(null);
useEffect(() => {
setValue(propValue);
}, [propValue]);
return <MockComponent setter={setValue} />;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{propValue: 'test'}],
};

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@@ -0,0 +1,73 @@
## Input
```javascript
// @validateNoDerivedComputationsInEffects
import {useEffect, useState, useRef} from 'react';
export default function Component({test}) {
const [local, setLocal] = useState('');
const myRef = useRef(null);
useEffect(() => {
setLocal(myRef.current + test);
}, [test]);
return <>{local}</>;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{test: 'testString'}],
};
```
## Code
```javascript
import { c as _c } from "react/compiler-runtime"; // @validateNoDerivedComputationsInEffects
import { useEffect, useState, useRef } from "react";
export default function Component(t0) {
const $ = _c(5);
const { test } = t0;
const [local, setLocal] = useState("");
const myRef = useRef(null);
let t1;
let t2;
if ($[0] !== test) {
t1 = () => {
setLocal(myRef.current + test);
};
t2 = [test];
$[0] = test;
$[1] = t1;
$[2] = t2;
} else {
t1 = $[1];
t2 = $[2];
}
useEffect(t1, t2);
let t3;
if ($[3] !== local) {
t3 = <>{local}</>;
$[3] = local;
$[4] = t3;
} else {
t3 = $[4];
}
return t3;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{ test: "testString" }],
};
```
### Eval output
(kind: ok) nulltestString

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@@ -0,0 +1,19 @@
// @validateNoDerivedComputationsInEffects
import {useEffect, useState, useRef} from 'react';
export default function Component({test}) {
const [local, setLocal] = useState('');
const myRef = useRef(null);
useEffect(() => {
setLocal(myRef.current + test);
}, [test]);
return <>{local}</>;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{test: 'testString'}],
};

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@@ -0,0 +1,75 @@
## Input
```javascript
// @validateNoDerivedComputationsInEffects
import {useEffect, useState} from 'react';
function Component({propValue, onChange}) {
const [value, setValue] = useState(null);
useEffect(() => {
setValue(propValue);
onChange();
}, [propValue]);
return <div>{value}</div>;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{propValue: 'test'}],
};
```
## Code
```javascript
import { c as _c } from "react/compiler-runtime"; // @validateNoDerivedComputationsInEffects
import { useEffect, useState } from "react";
function Component(t0) {
const $ = _c(7);
const { propValue, onChange } = t0;
const [value, setValue] = useState(null);
let t1;
if ($[0] !== onChange || $[1] !== propValue) {
t1 = () => {
setValue(propValue);
onChange();
};
$[0] = onChange;
$[1] = propValue;
$[2] = t1;
} else {
t1 = $[2];
}
let t2;
if ($[3] !== propValue) {
t2 = [propValue];
$[3] = propValue;
$[4] = t2;
} else {
t2 = $[4];
}
useEffect(t1, t2);
let t3;
if ($[5] !== value) {
t3 = <div>{value}</div>;
$[5] = value;
$[6] = t3;
} else {
t3 = $[6];
}
return t3;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{ propValue: "test" }],
};
```
### Eval output
(kind: exception) onChange is not a function

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@@ -0,0 +1,17 @@
// @validateNoDerivedComputationsInEffects
import {useEffect, useState} from 'react';
function Component({propValue, onChange}) {
const [value, setValue] = useState(null);
useEffect(() => {
setValue(propValue);
onChange();
}, [propValue]);
return <div>{value}</div>;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{propValue: 'test'}],
};

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@@ -0,0 +1,70 @@
## Input
```javascript
// @validateNoDerivedComputationsInEffects
import {useEffect, useState} from 'react';
function Component({propValue}) {
const [value, setValue] = useState(null);
useEffect(() => {
setValue(propValue);
globalCall();
}, [propValue]);
return <div>{value}</div>;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{propValue: 'test'}],
};
```
## Code
```javascript
import { c as _c } from "react/compiler-runtime"; // @validateNoDerivedComputationsInEffects
import { useEffect, useState } from "react";
function Component(t0) {
const $ = _c(5);
const { propValue } = t0;
const [value, setValue] = useState(null);
let t1;
let t2;
if ($[0] !== propValue) {
t1 = () => {
setValue(propValue);
globalCall();
};
t2 = [propValue];
$[0] = propValue;
$[1] = t1;
$[2] = t2;
} else {
t1 = $[1];
t2 = $[2];
}
useEffect(t1, t2);
let t3;
if ($[3] !== value) {
t3 = <div>{value}</div>;
$[3] = value;
$[4] = t3;
} else {
t3 = $[4];
}
return t3;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{ propValue: "test" }],
};
```
### Eval output
(kind: exception) globalCall is not defined

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@@ -0,0 +1,17 @@
// @validateNoDerivedComputationsInEffects
import {useEffect, useState} from 'react';
function Component({propValue}) {
const [value, setValue] = useState(null);
useEffect(() => {
setValue(propValue);
globalCall();
}, [propValue]);
return <div>{value}</div>;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{propValue: 'test'}],
};

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@@ -0,0 +1,49 @@
## Input
```javascript
// @validateNoDerivedComputationsInEffects
import {useEffect, useState} from 'react';
function Component({value, enabled}) {
const [localValue, setLocalValue] = useState('');
useEffect(() => {
if (enabled) {
setLocalValue(value);
} else {
setLocalValue('disabled');
}
}, [value, enabled]);
return <div>{localValue}</div>;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{value: 'test', enabled: true}],
};
```
## Error
```
Found 1 error:
Error: You might not need an effect. Derive values in render, not effects.
Derived values (From props: [value]) should be computed during render, rather than in effects. Using an effect triggers an additional render which can hurt performance and user experience, potentially briefly showing stale values to the user.
error.derived-state-conditionally-in-effect.ts:9:6
7 | useEffect(() => {
8 | if (enabled) {
> 9 | setLocalValue(value);
| ^^^^^^^^^^^^^^^^^^^^ This should be computed during render, not in an effect
10 | } else {
11 | setLocalValue('disabled');
12 | }
```

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@@ -0,0 +1,21 @@
// @validateNoDerivedComputationsInEffects
import {useEffect, useState} from 'react';
function Component({value, enabled}) {
const [localValue, setLocalValue] = useState('');
useEffect(() => {
if (enabled) {
setLocalValue(value);
} else {
setLocalValue('disabled');
}
}, [value, enabled]);
return <div>{localValue}</div>;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{value: 'test', enabled: true}],
};

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@@ -0,0 +1,39 @@
## Input
```javascript
// @validateNoDerivedComputationsInEffects
export default function Component(input = 'empty') {
const [currInput, setCurrInput] = useState(input);
useEffect(() => {
setCurrInput(input);
}, [input]);
return <div>{currInput}</div>;
}
```
## Error
```
Found 1 error:
Error: You might not need an effect. Derive values in render, not effects.
Derived values (From props: [input]) should be computed during render, rather than in effects. Using an effect triggers an additional render which can hurt performance and user experience, potentially briefly showing stale values to the user.
error.derived-state-from-default-props.ts:7:4
5 |
6 | useEffect(() => {
> 7 | setCurrInput(input);
| ^^^^^^^^^^^^^^^^^^^ This should be computed during render, not in an effect
8 | }, [input]);
9 |
10 | return <div>{currInput}</div>;
```

View File

@@ -0,0 +1,11 @@
// @validateNoDerivedComputationsInEffects
export default function Component(input = 'empty') {
const [currInput, setCurrInput] = useState(input);
useEffect(() => {
setCurrInput(input);
}, [input]);
return <div>{currInput}</div>;
}

View File

@@ -0,0 +1,53 @@
## Input
```javascript
// @validateNoDerivedComputationsInEffects
import {useEffect, useState} from 'react';
function Component({firstName}) {
const [lastName, setLastName] = useState(null);
const [fullName, setFullName] = useState(null);
const middleName = 'D.';
useEffect(() => {
setFullName(firstName + ' ' + middleName + ' ' + lastName);
}, [firstName, middleName, lastName]);
return (
<div>
<input value={lastName} onChange={e => setLastName(e.target.value)} />
<div>{fullName}</div>
</div>
);
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{firstName: 'John'}],
};
```
## Error
```
Found 1 error:
Error: You might not need an effect. Derive values in render, not effects.
Derived values (From props and local state: [firstName]) should be computed during render, rather than in effects. Using an effect triggers an additional render which can hurt performance and user experience, potentially briefly showing stale values to the user.
error.derived-state-from-prop-local-state-and-component-scope.ts:11:4
9 |
10 | useEffect(() => {
> 11 | setFullName(firstName + ' ' + middleName + ' ' + lastName);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This should be computed during render, not in an effect
12 | }, [firstName, middleName, lastName]);
13 |
14 | return (
```

View File

@@ -0,0 +1,25 @@
// @validateNoDerivedComputationsInEffects
import {useEffect, useState} from 'react';
function Component({firstName}) {
const [lastName, setLastName] = useState(null);
const [fullName, setFullName] = useState(null);
const middleName = 'D.';
useEffect(() => {
setFullName(firstName + ' ' + middleName + ' ' + lastName);
}, [firstName, middleName, lastName]);
return (
<div>
<input value={lastName} onChange={e => setLastName(e.target.value)} />
<div>{fullName}</div>
</div>
);
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{firstName: 'John'}],
};

View File

@@ -0,0 +1,45 @@
## Input
```javascript
// @validateNoDerivedComputationsInEffects
function Component({value}) {
const [localValue, setLocalValue] = useState('');
useEffect(() => {
setLocalValue(value);
document.title = `Value: ${value}`;
}, [value]);
return <div>{localValue}</div>;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{value: 'test'}],
};
```
## Error
```
Found 1 error:
Error: You might not need an effect. Derive values in render, not effects.
Derived values (From props: [value]) should be computed during render, rather than in effects. Using an effect triggers an additional render which can hurt performance and user experience, potentially briefly showing stale values to the user.
error.derived-state-from-prop-with-side-effect.ts:7:4
5 |
6 | useEffect(() => {
> 7 | setLocalValue(value);
| ^^^^^^^^^^^^^^^^^^^^ This should be computed during render, not in an effect
8 | document.title = `Value: ${value}`;
9 | }, [value]);
10 |
```

View File

@@ -0,0 +1,17 @@
// @validateNoDerivedComputationsInEffects
function Component({value}) {
const [localValue, setLocalValue] = useState('');
useEffect(() => {
setLocalValue(value);
document.title = `Value: ${value}`;
}, [value]);
return <div>{localValue}</div>;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{value: 'test'}],
};

View File

@@ -0,0 +1,50 @@
## Input
```javascript
// @validateNoDerivedComputationsInEffects
import {useEffect, useState} from 'react';
function Component({propValue}) {
const [value, setValue] = useState(null);
function localFunction() {
console.log('local function');
}
useEffect(() => {
setValue(propValue);
localFunction();
}, [propValue]);
return <div>{value}</div>;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{propValue: 'test'}],
};
```
## Error
```
Found 1 error:
Error: You might not need an effect. Derive values in render, not effects.
Derived values (From props: [propValue]) should be computed during render, rather than in effects. Using an effect triggers an additional render which can hurt performance and user experience, potentially briefly showing stale values to the user.
error.effect-contains-local-function-call.ts:12:4
10 |
11 | useEffect(() => {
> 12 | setValue(propValue);
| ^^^^^^^^^^^^^^^^^^^ This should be computed during render, not in an effect
13 | localFunction();
14 | }, [propValue]);
15 |
```

View File

@@ -0,0 +1,22 @@
// @validateNoDerivedComputationsInEffects
import {useEffect, useState} from 'react';
function Component({propValue}) {
const [value, setValue] = useState(null);
function localFunction() {
console.log('local function');
}
useEffect(() => {
setValue(propValue);
localFunction();
}, [propValue]);
return <div>{value}</div>;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{propValue: 'test'}],
};

View File

@@ -10,7 +10,7 @@ function BadExample() {
// 🔴 Avoid: redundant state and unnecessary Effect
const [fullName, setFullName] = useState('');
useEffect(() => {
setFullName(capitalize(firstName + ' ' + lastName));
setFullName(firstName + ' ' + lastName);
}, [firstName, lastName]);
return <div>{fullName}</div>;
@@ -24,13 +24,15 @@ function BadExample() {
```
Found 1 error:
Error: Values derived from props and state should be calculated during render, not in an effect. (https://react.dev/learn/you-might-not-need-an-effect#updating-state-based-on-props-or-state)
Error: You might not need an effect. Derive values in render, not effects.
Derived values (From local state: []) should be computed during render, rather than in effects. Using an effect triggers an additional render which can hurt performance and user experience, potentially briefly showing stale values to the user.
error.invalid-derived-computation-in-effect.ts:9:4
7 | const [fullName, setFullName] = useState('');
8 | useEffect(() => {
> 9 | setFullName(capitalize(firstName + ' ' + lastName));
| ^^^^^^^^^^^ Values derived from props and state should be calculated during render, not in an effect. (https://react.dev/learn/you-might-not-need-an-effect#updating-state-based-on-props-or-state)
> 9 | setFullName(firstName + ' ' + lastName);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This should be computed during render, not in an effect
10 | }, [firstName, lastName]);
11 |
12 | return <div>{fullName}</div>;

View File

@@ -6,7 +6,7 @@ function BadExample() {
// 🔴 Avoid: redundant state and unnecessary Effect
const [fullName, setFullName] = useState('');
useEffect(() => {
setFullName(capitalize(firstName + ' ' + lastName));
setFullName(firstName + ' ' + lastName);
}, [firstName, lastName]);
return <div>{fullName}</div>;

View File

@@ -0,0 +1,46 @@
## Input
```javascript
// @validateNoDerivedComputationsInEffects
import {useEffect, useState} from 'react';
export default function Component(props) {
const [displayValue, setDisplayValue] = useState('');
useEffect(() => {
const computed = props.prefix + props.value + props.suffix;
setDisplayValue(computed);
}, [props.prefix, props.value, props.suffix]);
return <div>{displayValue}</div>;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{prefix: '[', value: 'test', suffix: ']'}],
};
```
## Error
```
Found 1 error:
Error: You might not need an effect. Derive values in render, not effects.
Derived values (From props: [props]) should be computed during render, rather than in effects. Using an effect triggers an additional render which can hurt performance and user experience, potentially briefly showing stale values to the user.
error.invalid-derived-state-from-computed-props.ts:9:4
7 | useEffect(() => {
8 | const computed = props.prefix + props.value + props.suffix;
> 9 | setDisplayValue(computed);
| ^^^^^^^^^^^^^^^^^^^^^^^^^ This should be computed during render, not in an effect
10 | }, [props.prefix, props.value, props.suffix]);
11 |
12 | return <div>{displayValue}</div>;
```

View File

@@ -0,0 +1,18 @@
// @validateNoDerivedComputationsInEffects
import {useEffect, useState} from 'react';
export default function Component(props) {
const [displayValue, setDisplayValue] = useState('');
useEffect(() => {
const computed = props.prefix + props.value + props.suffix;
setDisplayValue(computed);
}, [props.prefix, props.value, props.suffix]);
return <div>{displayValue}</div>;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{prefix: '[', value: 'test', suffix: ']'}],
};

View File

@@ -0,0 +1,47 @@
## Input
```javascript
// @validateNoDerivedComputationsInEffects
import {useEffect, useState} from 'react';
export default function Component({props}) {
const [fullName, setFullName] = useState(
props.firstName + ' ' + props.lastName
);
useEffect(() => {
setFullName(props.firstName + ' ' + props.lastName);
}, [props.firstName, props.lastName]);
return <div>{fullName}</div>;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{props: {firstName: 'John', lastName: 'Doe'}}],
};
```
## Error
```
Found 1 error:
Error: You might not need an effect. Derive values in render, not effects.
Derived values (From props: [props]) should be computed during render, rather than in effects. Using an effect triggers an additional render which can hurt performance and user experience, potentially briefly showing stale values to the user.
error.invalid-derived-state-from-destructured-props.ts:10:4
8 |
9 | useEffect(() => {
> 10 | setFullName(props.firstName + ' ' + props.lastName);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This should be computed during render, not in an effect
11 | }, [props.firstName, props.lastName]);
12 |
13 | return <div>{fullName}</div>;
```

View File

@@ -0,0 +1,19 @@
// @validateNoDerivedComputationsInEffects
import {useEffect, useState} from 'react';
export default function Component({props}) {
const [fullName, setFullName] = useState(
props.firstName + ' ' + props.lastName
);
useEffect(() => {
setFullName(props.firstName + ' ' + props.lastName);
}, [props.firstName, props.lastName]);
return <div>{fullName}</div>;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{props: {firstName: 'John', lastName: 'Doe'}}],
};

View File

@@ -0,0 +1,82 @@
## Input
```javascript
// @validateNoDerivedComputationsInEffects
import {useEffect, useState, useRef} from 'react';
export default function Component({test}) {
const [local, setLocal] = useState('');
const myRef = useRef(null);
useEffect(() => {
if (myRef.current) {
setLocal(test + 'Available');
} else {
setLocal(test + 'NotAvailable');
}
}, [test]);
return <>{local}</>;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{test: 'testString'}],
};
```
## Code
```javascript
import { c as _c } from "react/compiler-runtime"; // @validateNoDerivedComputationsInEffects
import { useEffect, useState, useRef } from "react";
export default function Component(t0) {
const $ = _c(5);
const { test } = t0;
const [local, setLocal] = useState("");
const myRef = useRef(null);
let t1;
let t2;
if ($[0] !== test) {
t1 = () => {
if (myRef.current) {
setLocal(test + "Available");
} else {
setLocal(test + "NotAvailable");
}
};
t2 = [test];
$[0] = test;
$[1] = t1;
$[2] = t2;
} else {
t1 = $[1];
t2 = $[2];
}
useEffect(t1, t2);
let t3;
if ($[3] !== local) {
t3 = <>{local}</>;
$[3] = local;
$[4] = t3;
} else {
t3 = $[4];
}
return t3;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{ test: "testString" }],
};
```
### Eval output
(kind: ok) testStringNotAvailable

View File

@@ -0,0 +1,23 @@
// @validateNoDerivedComputationsInEffects
import {useEffect, useState, useRef} from 'react';
export default function Component({test}) {
const [local, setLocal] = useState('');
const myRef = useRef(null);
useEffect(() => {
if (myRef.current) {
setLocal(test + 'Available');
} else {
setLocal(test + 'NotAvailable');
}
}, [test]);
return <>{local}</>;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{test: 'testString'}],
};