stuff

buildfiles/app/node_modules/eslint/lib/rules/no-unneeded-ternary.js

@@ -0,0 +1,166 @@
+/**
+ * @fileoverview Rule to flag no-unneeded-ternary
+ * @author Gyandeep Singh
+ */
+
+"use strict";
+
+const astUtils = require("./utils/ast-utils");
+
+// Operators that always result in a boolean value
+const BOOLEAN_OPERATORS = new Set(["==", "===", "!=", "!==", ">", ">=", "<", "<=", "in", "instanceof"]);
+const OPERATOR_INVERSES = {
+    "==": "!=",
+    "!=": "==",
+    "===": "!==",
+    "!==": "==="
+
+    // Operators like < and >= are not true inverses, since both will return false with NaN.
+};
+const OR_PRECEDENCE = astUtils.getPrecedence({ type: "LogicalExpression", operator: "||" });
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = {
+    meta: {
+        type: "suggestion",
+
+        docs: {
+            description: "disallow ternary operators when simpler alternatives exist",
+            category: "Stylistic Issues",
+            recommended: false,
+            url: "https://eslint.org/docs/rules/no-unneeded-ternary"
+        },
+
+        schema: [
+            {
+                type: "object",
+                properties: {
+                    defaultAssignment: {
+                        type: "boolean",
+                        default: true
+                    }
+                },
+                additionalProperties: false
+            }
+        ],
+
+        fixable: "code",
+
+        messages: {
+            unnecessaryConditionalExpression: "Unnecessary use of boolean literals in conditional expression.",
+            unnecessaryConditionalAssignment: "Unnecessary use of conditional expression for default assignment."
+        }
+    },
+
+    create(context) {
+        const options = context.options[0] || {};
+        const defaultAssignment = options.defaultAssignment !== false;
+        const sourceCode = context.getSourceCode();
+
+        /**
+         * Test if the node is a boolean literal
+         * @param {ASTNode} node The node to report.
+         * @returns {boolean} True if the its a boolean literal
+         * @private
+         */
+        function isBooleanLiteral(node) {
+            return node.type === "Literal" && typeof node.value === "boolean";
+        }
+
+        /**
+         * Creates an expression that represents the boolean inverse of the expression represented by the original node
+         * @param {ASTNode} node A node representing an expression
+         * @returns {string} A string representing an inverted expression
+         */
+        function invertExpression(node) {
+            if (node.type === "BinaryExpression" && Object.prototype.hasOwnProperty.call(OPERATOR_INVERSES, node.operator)) {
+                const operatorToken = sourceCode.getFirstTokenBetween(
+                    node.left,
+                    node.right,
+                    token => token.value === node.operator
+                );
+                const text = sourceCode.getText();
+
+                return text.slice(node.range[0],
+                    operatorToken.range[0]) + OPERATOR_INVERSES[node.operator] + text.slice(operatorToken.range[1], node.range[1]);
+            }
+
+            if (astUtils.getPrecedence(node) < astUtils.getPrecedence({ type: "UnaryExpression" })) {
+                return `!(${astUtils.getParenthesisedText(sourceCode, node)})`;
+            }
+            return `!${astUtils.getParenthesisedText(sourceCode, node)}`;
+        }
+
+        /**
+         * Tests if a given node always evaluates to a boolean value
+         * @param {ASTNode} node An expression node
+         * @returns {boolean} True if it is determined that the node will always evaluate to a boolean value
+         */
+        function isBooleanExpression(node) {
+            return node.type === "BinaryExpression" && BOOLEAN_OPERATORS.has(node.operator) ||
+                node.type === "UnaryExpression" && node.operator === "!";
+        }
+
+        /**
+         * Test if the node matches the pattern id ? id : expression
+         * @param {ASTNode} node The ConditionalExpression to check.
+         * @returns {boolean} True if the pattern is matched, and false otherwise
+         * @private
+         */
+        function matchesDefaultAssignment(node) {
+            return node.test.type === "Identifier" &&
+                   node.consequent.type === "Identifier" &&
+                   node.test.name === node.consequent.name;
+        }
+
+        return {
+
+            ConditionalExpression(node) {
+                if (isBooleanLiteral(node.alternate) && isBooleanLiteral(node.consequent)) {
+                    context.report({
+                        node,
+                        messageId: "unnecessaryConditionalExpression",
+                        fix(fixer) {
+                            if (node.consequent.value === node.alternate.value) {
+
+                                // Replace `foo ? true : true` with just `true`, but don't replace `foo() ? true : true`
+                                return node.test.type === "Identifier" ? fixer.replaceText(node, node.consequent.value.toString()) : null;
+                            }
+                            if (node.alternate.value) {
+
+                                // Replace `foo() ? false : true` with `!(foo())`
+                                return fixer.replaceText(node, invertExpression(node.test));
+                            }
+
+                            // Replace `foo ? true : false` with `foo` if `foo` is guaranteed to be a boolean, or `!!foo` otherwise.
+
+                            return fixer.replaceText(node, isBooleanExpression(node.test) ? astUtils.getParenthesisedText(sourceCode, node.test) : `!${invertExpression(node.test)}`);
+                        }
+                    });
+                } else if (!defaultAssignment && matchesDefaultAssignment(node)) {
+                    context.report({
+                        node,
+                        messageId: "unnecessaryConditionalAssignment",
+                        fix: fixer => {
+                            const shouldParenthesizeAlternate =
+                                (
+                                    astUtils.getPrecedence(node.alternate) < OR_PRECEDENCE ||
+                                    astUtils.isCoalesceExpression(node.alternate)
+                                ) &&
+                                !astUtils.isParenthesised(sourceCode, node.alternate);
+                            const alternateText = shouldParenthesizeAlternate
+                                ? `(${sourceCode.getText(node.alternate)})`
+                                : astUtils.getParenthesisedText(sourceCode, node.alternate);
+                            const testText = astUtils.getParenthesisedText(sourceCode, node.test);
+
+                            return fixer.replaceText(node, `${testText} || ${alternateText}`);
+                        }
+                    });
+                }
+            }
+        };
+    }
+};