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prefer-string-slice: Handle negative length in .substr() #709

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merged 3 commits into from May 4, 2020
Merged

prefer-string-slice: Handle negative length in .substr() #709

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09a24bb
Rename `slice` to `sliceArguments`
fisker May 3, 2020
e8b85ac
Fix bug
fisker May 3, 2020
4db63d9
Fix code style
fisker May 3, 2020
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43 changes: 25 additions & 18 deletions rules/prefer-string-slice.js
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Expand Up @@ -63,35 +63,42 @@ const create = context => {
const firstArgument = argumentNodes[0] ? sourceCode.getText(argumentNodes[0]) : undefined;
const secondArgument = argumentNodes[1] ? sourceCode.getText(argumentNodes[1]) : undefined;

let slice;
let sliceArguments;

if (argumentNodes.length === 0) {
slice = [];
sliceArguments = [];
} else if (argumentNodes.length === 1) {
slice = [firstArgument];
sliceArguments = [firstArgument];
} else if (argumentNodes.length === 2) {
if (firstArgument === '0') {
slice = [firstArgument, secondArgument];
sliceArguments = [firstArgument];
if (isLiteralNumber(secondArgument) || isLengthProperty(argumentNodes[1])) {
sliceArguments.push(secondArgument);
} else if (typeof getNumericValue(argumentNodes[1]) === 'number') {
sliceArguments.push(Math.max(0, getNumericValue(argumentNodes[1])));
} else {
sliceArguments.push(`Math.max(0, ${secondArgument})`);
}
} else if (
isLiteralNumber(argumentNodes[0]) &&
isLiteralNumber(argumentNodes[1])
) {
slice = [
sliceArguments = [
firstArgument,
argumentNodes[0].value + argumentNodes[1].value
];
} else if (
isLikelyNumeric(argumentNodes[0]) &&
isLikelyNumeric(argumentNodes[1])
) {
slice = [firstArgument, firstArgument + ' + ' + secondArgument];
sliceArguments = [firstArgument, firstArgument + ' + ' + secondArgument];
}
}

if (slice) {
if (sliceArguments) {
const objectText = getNodeText(objectNode);

problem.fix = fixer => fixer.replaceText(node, `${objectText}.slice(${slice.join(', ')})`);
problem.fix = fixer => fixer.replaceText(node, `${objectText}.slice(${sliceArguments.join(', ')})`);
}

context.report(problem);
Expand All @@ -111,27 +118,27 @@ const create = context => {

const firstNumber = argumentNodes[0] ? getNumericValue(argumentNodes[0]) : undefined;

let slice;
let sliceArguments;

if (argumentNodes.length === 0) {
slice = [];
sliceArguments = [];
} else if (argumentNodes.length === 1) {
if (firstNumber !== undefined) {
slice = [Math.max(0, firstNumber)];
sliceArguments = [Math.max(0, firstNumber)];
} else if (isLengthProperty(argumentNodes[0])) {
slice = [firstArgument];
sliceArguments = [firstArgument];
} else {
slice = [`Math.max(0, ${firstArgument})`];
sliceArguments = [`Math.max(0, ${firstArgument})`];
}
} else if (argumentNodes.length === 2) {
const secondNumber = argumentNodes[1] ? getNumericValue(argumentNodes[1]) : undefined;
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If argumentNodes.length === 2 , argumentNodes[1] has to be a node.

const secondNumber = getNumericValue(argumentNodes[1]);

if (firstNumber !== undefined && secondNumber !== undefined) {
slice = firstNumber > secondNumber ?
sliceArguments = firstNumber > secondNumber ?
[Math.max(0, secondNumber), Math.max(0, firstNumber)] :
[Math.max(0, firstNumber), Math.max(0, secondNumber)];
} else if (firstNumber === 0 || secondNumber === 0) {
slice = [0, `Math.max(0, ${firstNumber === 0 ? secondArgument : firstArgument})`];
sliceArguments = [0, `Math.max(0, ${firstNumber === 0 ? secondArgument : firstArgument})`];
} else {
// As values aren't Literal, we can not know whether secondArgument will become smaller than the first or not, causing an issue:
// .substring(0, 2) and .substring(2, 0) returns the same result
Expand All @@ -142,9 +149,9 @@ const create = context => {
}
}

if (slice) {
if (sliceArguments) {
const objectText = getNodeText(objectNode);
problem.fix = fixer => fixer.replaceText(node, `${objectText}.slice(${slice.join(', ')})`);
problem.fix = fixer => fixer.replaceText(node, `${objectText}.slice(${sliceArguments.join(', ')})`);
}

context.report(problem);
Expand Down
30 changes: 29 additions & 1 deletion test/prefer-string-slice.js
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Expand Up @@ -84,7 +84,7 @@ ruleTester.run('prefer-string-slice', rule, {
`,
output: outdent`
const length = 123;
"foo".slice(0, length)
"foo".slice(0, Math.max(0, length))
`,
errors
},
Expand All @@ -99,6 +99,16 @@ ruleTester.run('prefer-string-slice', rule, {
`,
errors
},
{
code: '"foo".substr(0, -1)',
output: '"foo".slice(0, 0)',
errors
},
{
code: '"foo".substr(0, "foo".length)',
output: '"foo".slice(0, "foo".length)',
errors
},
{
code: outdent`
const length = 123;
Expand Down Expand Up @@ -138,6 +148,18 @@ ruleTester.run('prefer-string-slice', rule, {
code: '"foo".substr(1, 2)',
errors
},
// Extra arguments
{
code: 'foo.substr(1, 2, 3)',
output: 'foo.substr(1, 2, 3)',
errors
},
// #700
{
code: '"Sample".substr(0, "Sample".lastIndexOf("/"))',
output: '"Sample".slice(0, Math.max(0, "Sample".lastIndexOf("/")))',
errors
},

{
code: 'foo.substring()',
Expand Down Expand Up @@ -210,6 +232,12 @@ ruleTester.run('prefer-string-slice', rule, {
{
code: '"foo".substring(1, 3)',
errors
},
// Extra arguments
{
code: 'foo.substring(1, 2, 3)',
output: 'foo.substring(1, 2, 3)',
errors
}
]
});
Expand Down