Enable no-implicit-coercion rule (#10186)

.eslintrc.yml

@@ -27,6 +27,7 @@ rules:
     - devDependencies: ["tests*/**", "scripts/**"]
   import/order: error
   no-else-return: error
+  no-implicit-coercion: error
   no-inner-declarations: error
   no-unneeded-ternary: error
   no-useless-return: error

jest.config.js

@@ -3,7 +3,7 @@
 const installPrettier = require("./scripts/install-prettier");
 
 const isProduction = process.env.NODE_ENV === "production";
-const ENABLE_CODE_COVERAGE = !!process.env.ENABLE_CODE_COVERAGE;
+const ENABLE_CODE_COVERAGE = Boolean(process.env.ENABLE_CODE_COVERAGE);
 if (isProduction || process.env.INSTALL_PACKAGE) {
   process.env.PRETTIER_DIR = installPrettier();
 }

src/cli/format.js

@@ -197,13 +197,12 @@ function format(context, input, opt) {
         repeat +
         " times."
     );
-    // should be using `performance.now()`, but only `Date` is cross-platform enough
-    const now = Date.now ? () => Date.now() : () => +new Date();
     let totalMs = 0;
     for (let i = 0; i < repeat; ++i) {
-      const startMs = now();
+      // should be using `performance.now()`, but only `Date` is cross-platform enough
+      const startMs = Date.now();
       prettier.formatWithCursor(input, opt);
-      totalMs += now() - startMs;
+      totalMs += Date.now() - startMs;
     }
     const averageMs = totalMs / repeat;
     const results = {

src/config/resolve-config.js

@@ -68,9 +68,9 @@ function getExplorer(opts) {
 function _resolveConfig(filePath, opts, sync) {
   opts = { useCache: true, ...opts };
   const loadOpts = {
-    cache: !!opts.useCache,
-    sync: !!sync,
-    editorconfig: !!opts.editorconfig,
+    cache: Boolean(opts.useCache),
+    sync: Boolean(sync),
+    editorconfig: Boolean(opts.editorconfig),
   };
   const { load, search } = getExplorer(loadOpts);
   const loadEditorConfig = resolveEditorConfig.getLoadFunction(loadOpts);

src/document/doc-builders.js

@@ -95,7 +95,7 @@ function group(contents, opts = {}) {
     type: "group",
     id: opts.id,
     contents,
-    break: !!opts.shouldBreak,
+    break: Boolean(opts.shouldBreak),
     expandedStates: opts.expandedStates,
   };
 }

src/language-css/utils.js

@@ -96,7 +96,7 @@ function isSCSS(parser, text) {
 }
 
 function isSCSSVariable(node) {
-  return !!(node && node.type === "word" && node.value.startsWith("$"));
+  return Boolean(node && node.type === "word" && node.value.startsWith("$"));
 }
 
 function isWideKeywords(value) {

src/language-graphql/printer-graphql.js

@@ -35,7 +35,7 @@ function genericPrint(path, options, print) {
     }
     case "OperationDefinition": {
       const hasOperation = options.originalText[locStart(n)] !== "{";
-      const hasName = !!n.name;
+      const hasName = Boolean(n.name);
       return [
         hasOperation ? n.operation : "",
         hasOperation && hasName ? [" ", path.call(print, "name")] : "",

src/language-js/embed/html.js

@@ -67,7 +67,7 @@ function format(path, print, textToDoc, options, { parser }) {
         continue;
       }
 
-      const placeholderIndex = +component;
+      const placeholderIndex = Number(component);
       parts.push(expressionDocs[placeholderIndex]);
     }
 

src/language-js/needs-parens.js

@@ -581,7 +581,7 @@ function needsParens(path, options) {
     case "ArrowFunctionExpression":
       switch (parent.type) {
         case "PipelineTopicExpression":
-          return !!(node.extra && node.extra.parenthesized);
+          return Boolean(node.extra && node.extra.parenthesized);
 
         case "BinaryExpression":
           return (

src/language-js/print/class.js

@@ -101,8 +101,8 @@ function printHardlineAfterHeritage(node) {
 
 function hasMultipleHeritage(node) {
   return (
-    ["superClass", "extends", "mixins", "implements"].filter(
-      (key) => !!node[key]
+    ["superClass", "extends", "mixins", "implements"].filter((key) =>
+      Boolean(node[key])
     ).length > 1
   );
 }

src/language-js/print/jsx.js

@@ -713,7 +713,7 @@ function printJsx(path, options, print) {
     case "JSXAttribute":
       return printJsxAttribute(path, options, print);
     case "JSXIdentifier":
-      return "" + n.name;
+      return String(n.name);
     case "JSXNamespacedName":
       return join(":", [
         path.call(print, "namespace"),

src/language-js/printer-estree.js

@@ -490,7 +490,7 @@ function printPathNoParens(path, options, print, args) {
         return printNumber(n.raw);
       }
       if (typeof n.value !== "string") {
-        return "" + n.value;
+        return String(n.value);
       }
       return nodeStr(n, options);
     case "Directive":
@@ -873,7 +873,7 @@ function printPathNoParens(path, options, print, args) {
     case "ArrayTypeAnnotation":
       return [path.call(print, "elementType"), "[]"];
     case "BooleanLiteralTypeAnnotation":
-      return "" + n.value;
+      return String(n.value);
 
     case "EnumDeclaration":
       return ["enum ", path.call(print, "id"), " ", path.call(print, "body")];

src/language-js/utils.js

@@ -1160,7 +1160,7 @@ function getLeftMost(node) {
 
 function isBitwiseOperator(operator) {
   return (
-    !!bitshiftOperators[operator] ||
+    Boolean(bitshiftOperators[operator]) ||
     operator === "|" ||
     operator === "^" ||
     operator === "&"

src/language-markdown/printer-markdown.js

@@ -892,7 +892,7 @@ function clamp(value, min, max) {
 }
 
 function hasPrettierIgnore(path) {
-  const index = +path.getName();
+  const index = Number(path.getName());
 
   if (index === 0) {
     return false;

src/main/multiparser.js

@@ -37,12 +37,12 @@ function textToDoc(
       ...parentOptions,
       ...partialNextOptions,
       parentParser: parentOptions.parser,
-      embeddedInHtml: !!(
+      embeddedInHtml: Boolean(
         parentOptions.embeddedInHtml ||
-        parentOptions.parser === "html" ||
-        parentOptions.parser === "vue" ||
-        parentOptions.parser === "angular" ||
-        parentOptions.parser === "lwc"
+          parentOptions.parser === "html" ||
+          parentOptions.parser === "vue" ||
+          parentOptions.parser === "angular" ||
+          parentOptions.parser === "lwc"
       ),
       originalText: text,
     },

tests_integration/runPrettier.js

@@ -63,8 +63,8 @@ function runPrettier(dir, args = [], options = {}) {
   const originalStdoutIsTTY = process.stdout.isTTY;
 
   process.chdir(normalizeDir(dir));
-  process.stdin.isTTY = !!options.isTTY;
-  process.stdout.isTTY = !!options.stdoutIsTTY;
+  process.stdin.isTTY = Boolean(options.isTTY);
+  process.stdout.isTTY = Boolean(options.stdoutIsTTY);
   process.argv = ["path/to/node", "path/to/prettier/bin", ...args];
 
   jest.resetModules();
@@ -77,7 +77,7 @@ function runPrettier(dir, args = [], options = {}) {
     .mockImplementation(() => SynchronousPromise.resolve(options.input || ""));
   jest
     .spyOn(require(thirdParty), "isCI")
-    .mockImplementation(() => !!options.ci);
+    .mockImplementation(() => Boolean(options.ci));
   jest
     .spyOn(require(thirdParty), "cosmiconfig")
     .mockImplementation((moduleName, options) =>