Add isNonEmptyArray (#9902)

.eslintrc.yml

@@ -109,6 +109,7 @@ overrides:
   - files: src/**/*.js
     rules:
       prettier-internal-rules/prefer-fast-path-each: error
+      prettier-internal-rules/prefer-is-non-empty-array: error
   - files:
       - src/language-*/**/*.js
     rules:

scripts/tools/eslint-plugin-prettier-internal-rules/index.js

@@ -7,6 +7,7 @@ module.exports = {
     "jsx-identifier-case": require("./jsx-identifier-case"),
     "no-node-comments": require("./no-node-comments"),
     "prefer-fast-path-each": require("./prefer-fast-path-each"),
+    "prefer-is-non-empty-array": require("./prefer-is-non-empty-array"),
     "require-json-extensions": require("./require-json-extensions"),
   },
 };

scripts/tools/eslint-plugin-prettier-internal-rules/prefer-is-non-empty-array.js

@@ -0,0 +1,152 @@
+"use strict";
+
+const getLengthSelector = (path) =>
+  `[${path}.type="MemberExpression"][${path}.property.type="Identifier"][${path}.property.name="length"]`;
+const selector = [
+  "LogicalExpression",
+  ':not(FunctionDeclaration[id.name="isNonEmptyArray"] *)',
+  '[operator="&&"]',
+  `:matches(${[
+    // `&& foo.length`
+    getLengthSelector("right"),
+    // `&& foo.length !== 0`
+    // `&& foo.length > 0`
+    [
+      '[right.type="BinaryExpression"]',
+      ':matches([right.operator="!=="], [right.operator=">"])',
+      getLengthSelector("right.left"),
+      '[right.right.type="Literal"]',
+      '[right.right.raw="0"]',
+    ].join(""),
+  ].join(", ")})`,
+].join("");
+
+const negativeSelector = [
+  "LogicalExpression",
+  '[operator="||"]',
+  `:matches(${[
+    // `|| !foo.length`
+    [
+      '[right.type="UnaryExpression"]',
+      '[right.operator="!"]',
+      getLengthSelector("right.argument"),
+    ].join(""),
+    // `|| foo.length === 0`
+    [
+      '[right.type="BinaryExpression"]',
+      '[right.operator="==="]',
+      getLengthSelector("right.left"),
+      '[right.right.type="Literal"]',
+      '[right.right.raw="0"]',
+    ].join(""),
+  ].join(", ")})`,
+].join("");
+
+const isArrayIsArrayCall = (node) =>
+  node.type === "CallExpression" &&
+  node.callee.type === "MemberExpression" &&
+  node.callee.object.type === "Identifier" &&
+  node.callee.object.name === "Array" &&
+  node.callee.property.type === "Identifier" &&
+  node.callee.property.name === "isArray";
+
+const MESSAGE_ID = "prefer-is-non-empty-array";
+
+module.exports = {
+  meta: {
+    type: "suggestion",
+    docs: {
+      url:
+        "https://github.com/prettier/prettier/blob/master/scripts/eslint-plugin-prettier-internal-rules/prefer-is-non-empty-array.js",
+    },
+    messages: {
+      [MESSAGE_ID]: "Please use `isNonEmptyArray()`.",
+    },
+    fixable: "code",
+  },
+  create(context) {
+    const sourceCode = context.getSourceCode();
+
+    return {
+      [selector](node) {
+        let { left, right } = node;
+
+        while (left.type === "LogicalExpression" && left.operator === "&&") {
+          left = left.right;
+        }
+
+        let leftObject = left;
+        // `Array.isArray(foo)`
+        if (isArrayIsArrayCall(leftObject)) {
+          leftObject = leftObject.arguments[0];
+        }
+
+        const rightObject =
+          right.type === "BinaryExpression" ? right.left.object : right.object;
+        const objectText = sourceCode.getText(rightObject);
+        // Simple compare with code
+        if (sourceCode.getText(leftObject) !== objectText) {
+          return;
+        }
+
+        const [start] = left.range;
+        const [, end] = node.range;
+        context.report({
+          loc: {
+            start: sourceCode.getLocFromIndex(start),
+            end: sourceCode.getLocFromIndex(end),
+          },
+          messageId: MESSAGE_ID,
+          fix(fixer) {
+            return fixer.replaceTextRange(
+              [start, end],
+              `isNonEmptyArray(${objectText})`
+            );
+          },
+        });
+      },
+      [negativeSelector](node) {
+        let { left, right } = node;
+
+        while (left.type === "LogicalExpression" && left.operator === "||") {
+          left = left.right;
+        }
+
+        if (!left.type === "UnaryExpression" || left.operator !== "!") {
+          return;
+        }
+
+        const rightObject =
+          right.type === "UnaryExpression"
+            ? right.argument.object
+            : right.left.object;
+        let leftObject = left.argument;
+        if (isArrayIsArrayCall(leftObject)) {
+          leftObject = leftObject.arguments[0];
+        }
+
+        const objectText = sourceCode.getText(rightObject);
+        // Simple compare with code
+        if (sourceCode.getText(leftObject) !== objectText) {
+          return;
+        }
+
+        const [start] = left.range;
+        const [, end] = node.range;
+        context.report({
+          loc: {
+            start: sourceCode.getLocFromIndex(start),
+            end: sourceCode.getLocFromIndex(end),
+          },
+          messageId: MESSAGE_ID,
+          fix(fixer) {
+            return fixer.replaceTextRange(
+              [start, end],
+              `!isNonEmptyArray(${objectText})`
+            );
+          },
+        });
+      },
+    };
+  },
+};

src/common/util.js

@@ -624,6 +624,10 @@ function getShebang(text) {
   return text.slice(0, index);
 }
 
+function isNonEmptyArray(object) {
+  return Array.isArray(object) && object.length > 0;
+}
+
 module.exports = {
   inferParserByLanguage,
   replaceEndOfLineWith,
@@ -660,4 +664,5 @@ module.exports = {
   addTrailingComment,
   isFrontMatterNode,
   getShebang,
+  isNonEmptyArray,
 };

src/language-css/printer-postcss.js

@@ -6,6 +6,7 @@ const {
   hasNewline,
   isFrontMatterNode,
   isNextLineEmpty,
+  isNonEmptyArray,
 } = require("../common/util");
 const {
   builders: {
@@ -469,7 +470,7 @@ function genericPrint(path, options, print) {
     case "selector-pseudo": {
       return concat([
         maybeToLowerCase(node.value),
-        node.nodes && node.nodes.length > 0
+        isNonEmptyArray(node.nodes)
           ? concat(["(", join(", ", path.map(print, "nodes")), ")"])
           : "",
       ]);

src/language-css/utils.js

@@ -1,5 +1,6 @@
 "use strict";
 
+const { isNonEmptyArray } = require("../common/util");
 const colorAdjusterFunctions = new Set([
   "red",
   "green",
@@ -59,7 +60,7 @@ function getPropOfDeclNode(path) {
 }
 
 function hasSCSSInterpolation(groupList) {
-  if (groupList && groupList.length) {
+  if (isNonEmptyArray(groupList)) {
     for (let i = groupList.length - 1; i > 0; i--) {
       // If we find `#{`, return true.
       if (
@@ -76,7 +77,7 @@ function hasSCSSInterpolation(groupList) {
 }
 
 function hasStringOrFunction(groupList) {
-  if (groupList && groupList.length) {
+  if (isNonEmptyArray(groupList)) {
     for (let i = 0; i < groupList.length; i++) {
       if (groupList[i].type === "string" || groupList[i].type === "func") {
         return true;

src/language-graphql/printer-graphql.js

@@ -3,7 +3,7 @@
 const {
   builders: { concat, join, hardline, line, softline, group, indent, ifBreak },
 } = require("../document");
-const { isNextLineEmpty } = require("../common/util");
+const { isNextLineEmpty, isNonEmptyArray } = require("../common/util");
 const { insertPragma } = require("./pragma");
 const { locStart, locEnd } = require("./loc");
 
@@ -39,7 +39,7 @@ function genericPrint(path, options, print) {
       return concat([
         hasOperation ? n.operation : "",
         hasOperation && hasName ? concat([" ", path.call(print, "name")]) : "",
-        n.variableDefinitions && n.variableDefinitions.length
+        isNonEmptyArray(n.variableDefinitions)
           ? group(
               concat([
                 "(",
@@ -66,7 +66,7 @@ function genericPrint(path, options, print) {
       return concat([
         "fragment ",
         path.call(print, "name"),
-        n.variableDefinitions && n.variableDefinitions.length
+        isNonEmptyArray(n.variableDefinitions)
           ? group(
               concat([
                 "(",

src/language-html/ast.js

@@ -1,5 +1,6 @@
 "use strict";
 
+const { isNonEmptyArray } = require("../common/util");
 const NODES_KEYS = {
   attrs: true,
   children: true,
@@ -71,13 +72,11 @@ class Node {
   }
 
   get firstChild() {
-    return this.children && this.children.length !== 0
-      ? this.children[0]
-      : null;
+    return isNonEmptyArray(this.children) ? this.children[0] : null;
   }
 
   get lastChild() {
-    return this.children && this.children.length !== 0
+    return isNonEmptyArray(this.children)
       ? this.children[this.children.length - 1]
       : null;
   }

src/language-html/printer-html.js

@@ -18,7 +18,7 @@ const {
   },
   utils: { mapDoc, cleanDoc },
 } = require("../document");
-const { replaceEndOfLineWith } = require("../common/util");
+const { replaceEndOfLineWith, isNonEmptyArray } = require("../common/util");
 const { print: printFrontMatter } = require("../utils/front-matter");
 const clean = require("./clean");
 const {
@@ -657,7 +657,7 @@ function getNodeContent(node, options) {
 function printAttributes(path, options, print) {
   const node = path.getValue();
 
-  if (!node.attrs || node.attrs.length === 0) {
+  if (!isNonEmptyArray(node.attrs)) {
     return node.isSelfClosing
       ? /**
          *     <br />

src/language-js/comments.js

@@ -10,6 +10,7 @@ const {
   addTrailingComment,
   addDanglingComment,
   getNextNonSpaceNonCommentCharacterIndex,
+  isNonEmptyArray,
 } = require("../common/util");
 const {
   isBlockComment,
@@ -386,8 +387,7 @@ function handleClassComments({
       enclosingNode.type === "TSInterfaceDeclaration")
   ) {
     if (
-      enclosingNode.decorators &&
-      enclosingNode.decorators.length > 0 &&
+      isNonEmptyArray(enclosingNode.decorators) &&
       !(followingNode && followingNode.type === "Decorator")
     ) {
       addTrailingComment(
@@ -924,7 +924,7 @@ function getCommentChildNodes(node, options) {
     node.value.type === "FunctionExpression" &&
     getFunctionParameters(node.value).length === 0 &&
     !node.value.returnType &&
-    (!node.value.typeParameters || node.value.typeParameters.length === 0) &&
+    !isNonEmptyArray(node.value.typeParameters) &&
     node.value.body
   ) {
     return [...(node.decorators || []), node.key, node.value.body];

src/language-js/embed/css.js

@@ -1,5 +1,6 @@
 "use strict";
 
+const { isNonEmptyArray } = require("../../common/util");
 const {
   builders: { indent, hardline, softline, concat },
   utils: { mapDoc, replaceNewlinesWithLiterallines, cleanDoc },
@@ -52,7 +53,7 @@ function transformCssDoc(quasisDoc, parentNode, expressionDocs) {
 // returns a new doc with all the placeholders replaced,
 // or null if it couldn't replace any expression
 function replacePlaceholders(quasisDoc, expressionDocs) {
-  if (!expressionDocs || !expressionDocs.length) {
+  if (!isNonEmptyArray(expressionDocs)) {
     return quasisDoc;
   }
   let replaceCounter = 0;

src/language-js/loc.js

@@ -1,5 +1,7 @@
 "use strict";
 
+const { isNonEmptyArray } = require("../common/util");
+
 /**
  * @typedef {import("./types/estree").Node} Node
  */
@@ -12,7 +14,7 @@ function locStart(node, opts) {
     const decorators =
       (node.declaration && node.declaration.decorators) || node.decorators;
 
-    if (decorators && decorators.length > 0) {
+    if (isNonEmptyArray(decorators)) {
       return locStart(decorators[0]);
     }
   }

src/language-js/print/assignment.js

@@ -1,5 +1,6 @@
 "use strict";
 
+const { isNonEmptyArray } = require("../../common/util");
 const {
   builders: { concat, line, group, indent },
 } = require("../../document");
@@ -69,8 +70,7 @@ function printAssignmentRight(leftNode, rightNode, printedRight, options) {
       !shouldInlineLogicalExpression(rightNode.test)) ||
     rightNode.type === "StringLiteralTypeAnnotation" ||
     (rightNode.type === "ClassExpression" &&
-      rightNode.decorators &&
-      rightNode.decorators.length) ||
+      isNonEmptyArray(rightNode.decorators)) ||
     ((leftNode.type === "Identifier" ||
       isStringLiteral(leftNode) ||
       leftNode.type === "MemberExpression") &&

src/language-js/print/block.js

@@ -1,7 +1,7 @@
 "use strict";
 
 const { printDanglingComments } = require("../../main/comments");
-const { isNextLineEmpty } = require("../../common/util");
+const { isNextLineEmpty, isNonEmptyArray } = require("../../common/util");
 const {
   builders: { concat, hardline, indent },
 } = require("../../document");
@@ -21,7 +21,6 @@ function printBlock(path, options, print) {
   }
 
   parts.push("{");
-
   const printed = printBlockBody(path, options, print);
   if (printed) {
     parts.push(indent(concat([hardline, printed])), hardline);
@@ -58,8 +57,7 @@ function printBlock(path, options, print) {
 function printBlockBody(path, options, print) {
   const node = path.getValue();
 
-  const nodeHasDirectives =
-    Array.isArray(node.directives) && node.directives.length > 0;
+  const nodeHasDirectives = isNonEmptyArray(node.directives);
   const nodeHasBody = node.body.some((node) => node.type !== "EmptyStatement");
   const nodeHasComment = hasComment(node, CommentCheckFlags.Dangling);
 

src/language-js/print/class.js

@@ -1,5 +1,6 @@
 "use strict";
 
+const { isNonEmptyArray } = require("../../common/util");
 const { printComments, printDanglingComments } = require("../../main/comments");
 const {
   builders: { concat, join, line, hardline, softline, group, indent, ifBreak },
@@ -35,9 +36,9 @@ function printClass(path, options, print) {
   const groupMode =
     (n.id && hasComment(n.id, CommentCheckFlags.Trailing)) ||
     (n.superClass && hasComment(n.superClass)) ||
-    (n.extends && n.extends.length !== 0) || // DeclareClass
-    (n.mixins && n.mixins.length !== 0) ||
-    (n.implements && n.implements.length !== 0);
+    isNonEmptyArray(n.extends) || // DeclareClass
+    isNonEmptyArray(n.mixins) ||
+    isNonEmptyArray(n.implements);
 
   const partsGroup = [];
   const extendsParts = [];
@@ -113,7 +114,7 @@ function shouldIndentOnlyHeritageClauses(node) {
 
 function printList(path, options, print, listName) {
   const n = path.getValue();
-  if (!n[listName] || n[listName].length === 0) {
+  if (!isNonEmptyArray(n[listName])) {
     return "";
   }
 
@@ -158,7 +159,7 @@ function printClassMethod(path, options, print) {
   const n = path.getValue();
   const parts = [];
 
-  if (n.decorators && n.decorators.length !== 0) {
+  if (isNonEmptyArray(n.decorators)) {
     parts.push(printDecorators(path, options, print));
   }
   if (n.accessibility) {
@@ -197,7 +198,7 @@ function printClassProperty(path, options, print) {
   const parts = [];
   const semi = options.semi ? ";" : "";
 
-  if (n.decorators && n.decorators.length !== 0) {
+  if (isNonEmptyArray(n.decorators)) {
     parts.push(printDecorators(path, options, print));
   }
   if (n.accessibility) {

src/language-js/print/interface.js

@@ -1,5 +1,6 @@
 "use strict";
 
+const { isNonEmptyArray } = require("../../common/util");
 const {
   builders: { concat, join, line, group, indent, ifBreak },
 } = require("../../document");
@@ -41,7 +42,7 @@ function printInterface(path, options, print) {
       CommentCheckFlags.Trailing | CommentCheckFlags.Line
     );
 
-  if (n.extends && n.extends.length !== 0) {
+  if (isNonEmptyArray(n.extends)) {
     extendsParts.push(
       shouldIndentOnlyHeritageClauses
         ? ifBreak(" ", line, {
@@ -57,7 +58,7 @@ function printInterface(path, options, print) {
 
   if (
     (n.id && hasComment(n.id, CommentCheckFlags.Trailing)) ||
-    (n.extends && n.extends.length !== 0)
+    isNonEmptyArray(n.extends)
   ) {
     const printedExtends = concat(extendsParts);
     if (shouldIndentOnlyHeritageClauses) {

src/language-js/print/misc.js

@@ -1,5 +1,6 @@
 "use strict";
 
+const { isNonEmptyArray } = require("../../common/util");
 const {
   builders: { concat, indent, join, line },
 } = require("../../document");
@@ -67,7 +68,7 @@ function printBindExpressionCallee(path, options, print) {
 
 function printTypeScriptModifiers(path, options, print) {
   const n = path.getValue();
-  if (!n.modifiers || !n.modifiers.length) {
+  if (!isNonEmptyArray(n.modifiers)) {
     return "";
   }
   return concat([join(" ", path.map(print, "modifiers")), " "]);

src/language-js/print/module.js

@@ -1,5 +1,6 @@
 "use strict";
 
+const { isNonEmptyArray } = require("../../common/util");
 const {
   builders: { concat, softline, group, indent, join, line, ifBreak, hardline },
 } = require("../../document");
@@ -168,7 +169,7 @@ function printModuleSpecifiers(path, options, print) {
   /** @type{Doc[]} */
   const parts = [" "];
 
-  if (node.specifiers && node.specifiers.length > 0) {
+  if (isNonEmptyArray(node.specifiers)) {
     const standaloneSpecifiers = [];
     const groupedSpecifiers = [];
 
@@ -246,7 +247,7 @@ function shouldNotPrintSpecifiers(node, options) {
 
   if (
     type !== "ImportDeclaration" ||
-    (Array.isArray(specifiers) && specifiers.length > 0) ||
+    isNonEmptyArray(specifiers) ||
     importKind === "type"
   ) {
     return false;
@@ -260,7 +261,7 @@ function shouldNotPrintSpecifiers(node, options) {
 
 function printImportAssertions(path, options, print) {
   const node = path.getNode();
-  if (Array.isArray(node.assertions) && node.assertions.length !== 0) {
+  if (isNonEmptyArray(node.assertions)) {
     return concat([
       " assert {",
       options.bracketSpacing ? " " : "",

src/language-js/printer-estree.js

@@ -12,6 +12,7 @@ const {
   printString,
   printNumber,
   isNextLineEmpty,
+  isNonEmptyArray,
 } = require("../common/util");
 const {
   builders: {
@@ -127,8 +128,7 @@ function genericPrint(path, options, printPath, args) {
   ) {
     // their decorators are handled themselves
   } else if (
-    node.decorators &&
-    node.decorators.length > 0 &&
+    isNonEmptyArray(node.decorators) &&
     // If the parent node is an export declaration and the decorator
     // was written before the export, the export will be responsible
     // for printing the decorators.
@@ -162,8 +162,7 @@ function genericPrint(path, options, printPath, args) {
   } else if (
     isExportDeclaration(node) &&
     node.declaration &&
-    node.declaration.decorators &&
-    node.declaration.decorators.length > 0 &&
+    isNonEmptyArray(node.declaration.decorators) &&
     // Only print decorators here if they were written before the export,
     // otherwise they are printed by the node.declaration
     locStart(node, { ignoreDecorators: true }) >

src/language-js/utils.js

@@ -6,6 +6,7 @@ const {
   hasNewline,
   hasNewlineInRange,
   skipWhitespace,
+  isNonEmptyArray,
 } = require("../common/util");
 const { locStart, locEnd, hasSameLocStart } = require("./loc");
 
@@ -1470,7 +1471,7 @@ const getCommentTestFunction = (flags, fn) => {
  * @returns {boolean}
  */
 function hasComment(node, flags, fn) {
-  if (!node || !Array.isArray(node.comments) || node.comments.length === 0) {
+  if (!node || !isNonEmptyArray(node.comments)) {
     return false;
   }
   const test = getCommentTestFunction(flags, fn);

src/language-markdown/printer-markdown.js

@@ -5,6 +5,7 @@ const {
   getMinNotPresentContinuousCount,
   getMaxContinuousCount,
   getStringWidth,
+  isNonEmptyArray,
 } = require("../common/util");
 const {
   builders: {
@@ -773,7 +774,7 @@ function printChildren(path, options, print, events) {
 
 function getLastDescendantNode(node) {
   let current = node;
-  while (current.children && current.children.length !== 0) {
+  while (isNonEmptyArray(current.children)) {
     current = current.children[current.children.length - 1];
   }
   return current;

src/language-yaml/utils.js

@@ -1,6 +1,6 @@
 "use strict";
 
-const { getLast } = require("../common/util");
+const { getLast, isNonEmptyArray } = require("../common/util");
 
 function getAncestorCount(path, filter) {
   let counter = 0;
@@ -98,7 +98,7 @@ function isLastDescendantNode(path) {
 }
 
 function getLastDescendantNode(node) {
-  return "children" in node && node.children.length !== 0
+  return isNonEmptyArray(node.children)
     ? getLastDescendantNode(getLast(node.children))
     : node;
 }
@@ -124,7 +124,7 @@ function hasPrettierIgnore(path) {
 }
 
 function isEmptyNode(node) {
-  return (!node.children || node.children.length === 0) && !hasComments(node);
+  return !isNonEmptyArray(node.children) && !hasComments(node);
 }
 
 function hasComments(node) {
@@ -138,11 +138,11 @@ function hasComments(node) {
 }
 
 function hasLeadingComments(node) {
-  return node && node.leadingComments && node.leadingComments.length !== 0;
+  return node && isNonEmptyArray(node.leadingComments);
 }
 
 function hasMiddleComments(node) {
-  return node && node.middleComments && node.middleComments.length !== 0;
+  return node && isNonEmptyArray(node.middleComments);
 }
 
 function hasIndicatorComment(node) {
@@ -154,7 +154,7 @@ function hasTrailingComment(node) {
 }
 
 function hasEndComments(node) {
-  return node && node.endComments && node.endComments.length !== 0;
+  return node && isNonEmptyArray(node.endComments);
 }
 
 /**

src/main/comments.js

@@ -24,6 +24,7 @@ const {
   addLeadingComment,
   addDanglingComment,
   addTrailingComment,
+  isNonEmptyArray,
 } = require("../common/util");
 
 const childNodesCache = new WeakMap();
@@ -559,7 +560,7 @@ function printComments(path, print, options, needsSemi) {
   const printed = print(path);
   const comments = value && value.comments;
 
-  if (!comments || comments.length === 0) {
+  if (!isNonEmptyArray(comments)) {
     return prependCursorPlaceholder(path, options, printed);
   }