switch-exhaustiveness-check.js
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"use strict";
var __createBinding = (this && this.__createBinding) || (Object.create ? (function(o, m, k, k2) {
if (k2 === undefined) k2 = k;
Object.defineProperty(o, k2, { enumerable: true, get: function() { return m[k]; } });
}) : (function(o, m, k, k2) {
if (k2 === undefined) k2 = k;
o[k2] = m[k];
}));
var __setModuleDefault = (this && this.__setModuleDefault) || (Object.create ? (function(o, v) {
Object.defineProperty(o, "default", { enumerable: true, value: v });
}) : function(o, v) {
o["default"] = v;
});
var __importStar = (this && this.__importStar) || function (mod) {
if (mod && mod.__esModule) return mod;
var result = {};
if (mod != null) for (var k in mod) if (k !== "default" && Object.prototype.hasOwnProperty.call(mod, k)) __createBinding(result, mod, k);
__setModuleDefault(result, mod);
return result;
};
Object.defineProperty(exports, "__esModule", { value: true });
const ts = __importStar(require("typescript"));
const util_1 = require("../util");
const tsutils_1 = require("tsutils");
exports.default = util_1.createRule({
name: 'switch-exhaustiveness-check',
meta: {
type: 'suggestion',
docs: {
description: 'Exhaustiveness checking in switch with union type',
category: 'Best Practices',
recommended: false,
suggestion: true,
requiresTypeChecking: true,
},
schema: [],
messages: {
switchIsNotExhaustive: 'Switch is not exhaustive. Cases not matched: {{missingBranches}}',
addMissingCases: 'Add branches for missing cases.',
},
},
defaultOptions: [],
create(context) {
const sourceCode = context.getSourceCode();
const service = util_1.getParserServices(context);
const checker = service.program.getTypeChecker();
const compilerOptions = service.program.getCompilerOptions();
function getNodeType(node) {
const tsNode = service.esTreeNodeToTSNodeMap.get(node);
return util_1.getConstrainedTypeAtLocation(checker, tsNode);
}
function fixSwitch(fixer, node, missingBranchTypes, symbolName) {
var _a;
const lastCase = node.cases.length > 0 ? node.cases[node.cases.length - 1] : null;
const caseIndent = lastCase
? ' '.repeat(lastCase.loc.start.column)
: // if there are no cases, use indentation of the switch statement
// and leave it to user to format it correctly
' '.repeat(node.loc.start.column);
const missingCases = [];
for (const missingBranchType of missingBranchTypes) {
// While running this rule on checker.ts of TypeScript project
// the fix introduced a compiler error due to:
//
// type __String = (string & {
// __escapedIdentifier: void;
// }) | (void & {
// __escapedIdentifier: void;
// }) | InternalSymbolName;
//
// The following check fixes it.
if (missingBranchType.isIntersection()) {
continue;
}
const missingBranchName = (_a = missingBranchType.getSymbol()) === null || _a === void 0 ? void 0 : _a.escapedName;
let caseTest = checker.typeToString(missingBranchType);
if (symbolName &&
(missingBranchName || missingBranchName === '') &&
util_1.requiresQuoting(missingBranchName.toString(), compilerOptions.target)) {
caseTest = `${symbolName}['${missingBranchName}']`;
}
const errorMessage = `Not implemented yet: ${caseTest} case`;
missingCases.push(`case ${caseTest}: { throw new Error('${errorMessage}') }`);
}
const fixString = missingCases
.map(code => `${caseIndent}${code}`)
.join('\n');
if (lastCase) {
return fixer.insertTextAfter(lastCase, `\n${fixString}`);
}
// there were no existing cases
const openingBrace = sourceCode.getTokenAfter(node.discriminant, util_1.isOpeningBraceToken);
const closingBrace = sourceCode.getTokenAfter(node.discriminant, util_1.isClosingBraceToken);
return fixer.replaceTextRange([openingBrace.range[0], closingBrace.range[1]], ['{', fixString, `${caseIndent}}`].join('\n'));
}
function checkSwitchExhaustive(node) {
var _a;
const discriminantType = getNodeType(node.discriminant);
const symbolName = (_a = discriminantType.getSymbol()) === null || _a === void 0 ? void 0 : _a.escapedName;
if (discriminantType.isUnion()) {
const unionTypes = tsutils_1.unionTypeParts(discriminantType);
const caseTypes = new Set();
for (const switchCase of node.cases) {
if (switchCase.test === null) {
// Switch has 'default' branch - do nothing.
return;
}
caseTypes.add(getNodeType(switchCase.test));
}
const missingBranchTypes = unionTypes.filter(unionType => !caseTypes.has(unionType));
if (missingBranchTypes.length === 0) {
// All cases matched - do nothing.
return;
}
context.report({
node: node.discriminant,
messageId: 'switchIsNotExhaustive',
data: {
missingBranches: missingBranchTypes
.map(missingType => {
var _a;
return tsutils_1.isTypeFlagSet(missingType, ts.TypeFlags.ESSymbolLike)
? `typeof ${(_a = missingType.getSymbol()) === null || _a === void 0 ? void 0 : _a.escapedName}`
: checker.typeToString(missingType);
})
.join(' | '),
},
suggest: [
{
messageId: 'addMissingCases',
fix(fixer) {
return fixSwitch(fixer, node, missingBranchTypes, symbolName === null || symbolName === void 0 ? void 0 : symbolName.toString());
},
},
],
});
}
}
return {
SwitchStatement: checkSwitchExhaustive,
};
},
});
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