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Update: for yoda, add a fixer #7199

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Sep 29, 2016
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Update: for yoda, add a fixer #7199

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2 changes: 2 additions & 0 deletions docs/rules/yoda.md
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Original file line number Diff line number Diff line change
@@ -1,5 +1,7 @@
# Require or disallow Yoda Conditions (yoda)

(fixable) The `--fix` option on the [command line](../user-guide/command-line-interface#fix) automatically fixes problems reported by this rule.

Yoda conditions are so named because the literal value of the condition comes first while the variable comes second. For example, the following is a Yoda condition:

```js
Expand Down
67 changes: 40 additions & 27 deletions lib/rules/yoda.js
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Expand Up @@ -141,7 +141,9 @@ module.exports = {
},
additionalProperties: false
}
]
],

fixable: "code"
},

create(context) {
Expand Down Expand Up @@ -219,46 +221,57 @@ module.exports = {
isParenWrapped());
}

const OPERATOR_FLIP_MAP = {
"===": "===",
"!==": "!==",
"==": "==",
"!=": "!=",
"<": ">",
">": "<",
"<=": ">=",
">=": "<="
};

/**
* Returns a string representation of a BinaryExpression node with its sides/operator flipped around.
* @param {ASTNode} node The BinaryExpression node
* @returns {string} A string representation of the node with the sides and operator flipped
*/
function getFlippedString(node) {
const operatorToken = sourceCode.getTokensBetween(node.left, node.right).find(token => token.value === node.operator);
const textBeforeOperator = sourceCode.getText().slice(node.left.range[1], operatorToken.range[0]);
const textAfterOperator = sourceCode.getText().slice(operatorToken.range[1], node.right.range[0]);
const leftText = sourceCode.getText(node.left);
const rightText = sourceCode.getText(node.right);

return rightText + textBeforeOperator + OPERATOR_FLIP_MAP[operatorToken.value] + textAfterOperator + leftText;
}

//--------------------------------------------------------------------------
// Public
//--------------------------------------------------------------------------

return {
BinaryExpression: always ? function(node) {

// Comparisons must always be yoda-style: if ("blue" === color)
if (
(node.right.type === "Literal" || looksLikeLiteral(node.right)) &&
!(node.left.type === "Literal" || looksLikeLiteral(node.left)) &&
!(!isEqualityOperator(node.operator) && onlyEquality) &&
isComparisonOperator(node.operator) &&
!(exceptRange && isRangeTest(context.getAncestors().pop()))
) {
context.report({
node,
message: "Expected literal to be on the left side of {{operator}}.",
data: {
operator: node.operator
}
});
}

} : function(node) {
BinaryExpression(node) {
const expectedLiteral = always ? node.left : node.right;
const expectedNonLiteral = always ? node.right : node.left;

// Comparisons must never be yoda-style (default)
// If `expectedLiteral` is not a literal, and `expectedNonLiteral` is a literal, raise an error.
if (
(node.left.type === "Literal" || looksLikeLiteral(node.left)) &&
!(node.right.type === "Literal" || looksLikeLiteral(node.right)) &&
(expectedNonLiteral.type === "Literal" || looksLikeLiteral(expectedNonLiteral)) &&
!(expectedLiteral.type === "Literal" || looksLikeLiteral(expectedLiteral)) &&
!(!isEqualityOperator(node.operator) && onlyEquality) &&
isComparisonOperator(node.operator) &&
!(exceptRange && isRangeTest(context.getAncestors().pop()))
) {
context.report({
node,
message: "Expected literal to be on the right side of {{operator}}.",
message: "Expected literal to be on the {{expectedSide}} side of {{operator}}.",
data: {
operator: node.operator
}
operator: node.operator,
expectedSide: always ? "left" : "right"
},
fix: fixer => fixer.replaceText(node, getFlippedString(node))
});
}

Expand Down
69 changes: 68 additions & 1 deletion tests/lib/rules/yoda.js
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Original file line number Diff line number Diff line change
Expand Up @@ -79,6 +79,7 @@ ruleTester.run("yoda", rule, {

{
code: "if (\"red\" == value) {}",
output: "if (value == \"red\") {}",
options: ["never"],
errors: [
{
Expand All @@ -89,6 +90,7 @@ ruleTester.run("yoda", rule, {
},
{
code: "if (true === value) {}",
output: "if (value === true) {}",
options: ["never"],
errors: [
{
Expand All @@ -99,6 +101,7 @@ ruleTester.run("yoda", rule, {
},
{
code: "if (5 != value) {}",
output: "if (value != 5) {}",
options: ["never"],
errors: [
{
Expand All @@ -109,6 +112,7 @@ ruleTester.run("yoda", rule, {
},
{
code: "if (null !== value) {}",
output: "if (value !== null) {}",
options: ["never"],
errors: [
{
Expand All @@ -119,6 +123,7 @@ ruleTester.run("yoda", rule, {
},
{
code: "if (\"red\" <= value) {}",
output: "if (value >= \"red\") {}",
options: ["never"],
errors: [
{
Expand All @@ -129,6 +134,7 @@ ruleTester.run("yoda", rule, {
},
{
code: "if (true >= value) {}",
output: "if (value <= true) {}",
options: ["never"],
errors: [
{
Expand All @@ -139,6 +145,7 @@ ruleTester.run("yoda", rule, {
},
{
code: "var foo = (5 < value) ? true : false",
output: "var foo = (value > 5) ? true : false",
options: ["never"],
errors: [
{
Expand All @@ -149,6 +156,7 @@ ruleTester.run("yoda", rule, {
},
{
code: "function foo() { return (null > value); }",
output: "function foo() { return (value < null); }",
options: ["never"],
errors: [
{
Expand All @@ -159,6 +167,7 @@ ruleTester.run("yoda", rule, {
},
{
code: "if (-1 < str.indexOf(substr)) {}",
output: "if (str.indexOf(substr) > -1) {}",
options: ["never"],
errors: [
{
Expand All @@ -169,6 +178,7 @@ ruleTester.run("yoda", rule, {
},
{
code: "if (value == \"red\") {}",
output: "if (\"red\" == value) {}",
options: ["always"],
errors: [
{
Expand All @@ -179,6 +189,7 @@ ruleTester.run("yoda", rule, {
},
{
code: "if (value === true) {}",
output: "if (true === value) {}",
options: ["always"],
errors: [
{
Expand All @@ -189,6 +200,7 @@ ruleTester.run("yoda", rule, {
},
{
code: "if (a < 0 && 0 <= b && b < 1) {}",
output: "if (a < 0 && b >= 0 && b < 1) {}",
options: ["never", { exceptRange: true }],
errors: [
{
Expand All @@ -199,6 +211,7 @@ ruleTester.run("yoda", rule, {
},
{
code: "if (0 <= a && a < 1 && b < 1) {}",
output: "if (a >= 0 && a < 1 && b < 1) {}",
options: ["never", { exceptRange: true }],
errors: [
{
Expand All @@ -209,6 +222,7 @@ ruleTester.run("yoda", rule, {
},
{
code: "if (1 < a && a < 0) {}",
output: "if (a > 1 && a < 0) {}",
options: ["never", { exceptRange: true }],
errors: [
{
Expand All @@ -219,6 +233,7 @@ ruleTester.run("yoda", rule, {
},
{
code: "0 < a && a < 1",
output: "a > 0 && a < 1",
options: ["never", { exceptRange: true }],
errors: [
{
Expand All @@ -229,6 +244,7 @@ ruleTester.run("yoda", rule, {
},
{
code: "var a = b < 0 || 1 <= b;",
output: "var a = b < 0 || b >= 1;",
options: ["never", { exceptRange: true }],
errors: [
{
Expand All @@ -239,6 +255,7 @@ ruleTester.run("yoda", rule, {
},
{
code: "if (0 <= x && x < -1) {}",
output: "if (x >= 0 && x < -1) {}",
options: ["never", { exceptRange: true }],
errors: [
{
Expand All @@ -249,6 +266,7 @@ ruleTester.run("yoda", rule, {
},
{
code: "var a = (b < 0 && 0 <= b);",
output: "var a = (0 > b && 0 <= b);",
options: ["always", { exceptRange: true }],
errors: [
{
Expand All @@ -259,6 +277,7 @@ ruleTester.run("yoda", rule, {
},
{
code: "if (0 <= a[b] && a['b'] < 1) {}",
output: "if (a[b] >= 0 && a['b'] < 1) {}",
options: ["never", { exceptRange: true }],
errors: [
{
Expand All @@ -269,6 +288,7 @@ ruleTester.run("yoda", rule, {
},
{
code: "if (0 <= a[b()] && a[b()] < 1) {}",
output: "if (a[b()] >= 0 && a[b()] < 1) {}",
options: ["never", { exceptRange: true }],
errors: [
{
Expand All @@ -279,6 +299,7 @@ ruleTester.run("yoda", rule, {
},
{
code: "if (3 == a) {}",
output: "if (a == 3) {}",
options: ["never", { onlyEquality: true }],
errors: [
{
Expand All @@ -289,6 +310,7 @@ ruleTester.run("yoda", rule, {
},
{
code: "foo(3 === a);",
output: "foo(a === 3);",
options: ["never", { onlyEquality: true }],
errors: [
{
Expand All @@ -299,6 +321,7 @@ ruleTester.run("yoda", rule, {
},
{
code: "foo(a === 3);",
output: "foo(3 === a);",
options: ["always", { onlyEquality: true }],
errors: [
{
Expand All @@ -309,13 +332,57 @@ ruleTester.run("yoda", rule, {
},
{
code: "if (0 <= x && x < 1) {}",
output: "if (x >= 0 && x < 1) {}",
errors: [
{
message: "Expected literal to be on the right side of <=.",
type: "BinaryExpression"
}
]
},
{
code: "if ( /* a */ 0 /* b */ < /* c */ foo /* d */ ) {}",
output: "if ( /* a */ foo /* b */ > /* c */ 0 /* d */ ) {}",
options: ["never"],
errors: [
{
message: "Expected literal to be on the right side of <.",
type: "BinaryExpression"
}
]
},
{
code: "if ( /* a */ foo /* b */ > /* c */ 0 /* d */ ) {}",
output: "if ( /* a */ 0 /* b */ < /* c */ foo /* d */ ) {}",
options: ["always"],
errors: [
{
message: "Expected literal to be on the left side of >.",
type: "BinaryExpression"
}
]
},
{
code: "if (foo()===1) {}",
output: "if (1===foo()) {}",
options: ["always"],
errors: [
{
message: "Expected literal to be on the left side of ===.",
type: "BinaryExpression"
}
]
},
{
code: "if (foo() === 1) {}",
output: "if (1 === foo()) {}",
options: ["always"],
errors: [
{
message: "Expected literal to be on the left side of ===.",
type: "BinaryExpression"
}
]
}

]
});