assignment.js

"use strict";

const { isNonEmptyArray, getStringWidth } = require("../../common/util.js");
const {
  builders: { line, group, indent, indentIfBreak, lineSuffixBoundary },
  utils: { cleanDoc, willBreak, canBreak },
} = require("../../document/index.js");
const {
  hasLeadingOwnLineComment,
  isBinaryish,
  isStringLiteral,
  isLiteral,
  isNumericLiteral,
  isCallExpression,
  isMemberExpression,
  getCallArguments,
  rawText,
  hasComment,
  isSignedNumericLiteral,
  isObjectProperty,
} = require("../utils/index.js");
const { shouldInlineLogicalExpression } = require("./binaryish.js");
const { printCallExpression } = require("./call-expression.js");

function printAssignment(
  path,
  options,
  print,
  leftDoc,
  operator,
  rightPropertyName
) {
  const layout = chooseLayout(path, options, print, leftDoc, rightPropertyName);

  const rightDoc = print(rightPropertyName, { assignmentLayout: layout });

  switch (layout) {
    // First break after operator, then the sides are broken independently on their own lines
    case "break-after-operator":
      return group([group(leftDoc), operator, group(indent([line, rightDoc]))]);

    // First break right-hand side, then left-hand side
    case "never-break-after-operator":
      return group([group(leftDoc), operator, " ", rightDoc]);

    // First break right-hand side, then after operator
    case "fluid": {
      const groupId = Symbol("assignment");
      return group([
        group(leftDoc),
        operator,
        group(indent(line), { id: groupId }),
        lineSuffixBoundary,
        indentIfBreak(rightDoc, { groupId }),
      ]);
    }

    case "break-lhs":
      return group([leftDoc, operator, " ", group(rightDoc)]);

    // Parts of assignment chains aren't wrapped in groups.
    // Once one of them breaks, the chain breaks too.
    case "chain":
      return [group(leftDoc), operator, line, rightDoc];

    case "chain-tail":
      return [group(leftDoc), operator, indent([line, rightDoc])];

    case "chain-tail-arrow-chain":
      return [group(leftDoc), operator, rightDoc];

    case "only-left":
      return leftDoc;
  }
}

function printAssignmentExpression(path, options, print) {
  const node = path.getValue();
  return printAssignment(
    path,
    options,
    print,
    print("left"),
    [" ", node.operator],
    "right"
  );
}

function printVariableDeclarator(path, options, print) {
  return printAssignment(path, options, print, print("id"), " =", "init");
}

function chooseLayout(path, options, print, leftDoc, rightPropertyName) {
  const node = path.getValue();
  const rightNode = node[rightPropertyName];

  if (!rightNode) {
    return "only-left";
  }

  // Short assignment chains (only 2 segments) are NOT formatted as chains.
  //   1) a = b = c; (expression statements)
  //   2) var/let/const a = b = c;

  const isTail = !isAssignment(rightNode);
  const shouldUseChainFormatting = path.match(
    isAssignment,
    isAssignmentOrVariableDeclarator,
    (node) =>
      !isTail ||
      (node.type !== "ExpressionStatement" &&
        node.type !== "VariableDeclaration")
  );
  if (shouldUseChainFormatting) {
    return !isTail
      ? "chain"
      : rightNode.type === "ArrowFunctionExpression" &&
        rightNode.body.type === "ArrowFunctionExpression"
      ? "chain-tail-arrow-chain"
      : "chain-tail";
  }
  const isHeadOfLongChain = !isTail && isAssignment(rightNode.right);

  if (
    isHeadOfLongChain ||
    hasLeadingOwnLineComment(options.originalText, rightNode)
  ) {
    return "break-after-operator";
  }

  if (
    (rightNode.type === "CallExpression" &&
      rightNode.callee.name === "require") ||
    // do not put values on a separate line from the key in json
    options.parser === "json5" ||
    options.parser === "json"
  ) {
    return "never-break-after-operator";
  }

  if (
    isComplexDestructuring(node) ||
    isComplexTypeAliasParams(node) ||
    hasComplexTypeAnnotation(node) ||
    (isArrowFunctionVariableDeclarator(node) && canBreak(leftDoc))
  ) {
    return "break-lhs";
  }

  // wrapping object properties with very short keys usually doesn't add much value
  const hasShortKey = isObjectPropertyWithShortKey(node, leftDoc, options);

  if (
    path.call(
      () => shouldBreakAfterOperator(path, options, print, hasShortKey),
      rightPropertyName
    )
  ) {
    return "break-after-operator";
  }

  if (
    hasShortKey ||
    rightNode.type === "TemplateLiteral" ||
    rightNode.type === "TaggedTemplateExpression" ||
    rightNode.type === "BooleanLiteral" ||
    isNumericLiteral(rightNode) ||
    rightNode.type === "ClassExpression"
  ) {
    return "never-break-after-operator";
  }

  return "fluid";
}

function shouldBreakAfterOperator(path, options, print, hasShortKey) {
  const rightNode = path.getValue();

  if (isBinaryish(rightNode) && !shouldInlineLogicalExpression(rightNode)) {
    return true;
  }

  switch (rightNode.type) {
    case "StringLiteralTypeAnnotation":
    case "SequenceExpression":
      return true;
    case "ConditionalExpression": {
      const { test } = rightNode;
      return isBinaryish(test) && !shouldInlineLogicalExpression(test);
    }
    case "ClassExpression":
      return isNonEmptyArray(rightNode.decorators);
  }

  if (hasShortKey) {
    return false;
  }

  let node = rightNode;
  const propertiesForPath = [];
  for (;;) {
    if (node.type === "UnaryExpression") {
      node = node.argument;
      propertiesForPath.push("argument");
    } else if (node.type === "TSNonNullExpression") {
      node = node.expression;
      propertiesForPath.push("expression");
    } else {
      break;
    }
  }
  if (
    isStringLiteral(node) ||
    path.call(
      () => isPoorlyBreakableMemberOrCallChain(path, options, print),
      ...propertiesForPath
    )
  ) {
    return true;
  }

  return false;
}

// prefer to break destructuring assignment
// if it includes default values or non-shorthand properties
function isComplexDestructuring(node) {
  if (isAssignmentOrVariableDeclarator(node)) {
    const leftNode = node.left || node.id;
    return (
      leftNode.type === "ObjectPattern" &&
      leftNode.properties.length > 2 &&
      leftNode.properties.some(
        (property) =>
          isObjectProperty(property) &&
          (!property.shorthand ||
            (property.value && property.value.type === "AssignmentPattern"))
      )
    );
  }
  return false;
}

function isAssignment(node) {
  return node.type === "AssignmentExpression";
}

function isAssignmentOrVariableDeclarator(node) {
  return isAssignment(node) || node.type === "VariableDeclarator";
}

function isComplexTypeAliasParams(node) {
  const typeParams = getTypeParametersFromTypeAlias(node);
  if (isNonEmptyArray(typeParams)) {
    const constraintPropertyName =
      node.type === "TSTypeAliasDeclaration" ? "constraint" : "bound";
    if (
      typeParams.length > 1 &&
      typeParams.some((param) => param[constraintPropertyName] || param.default)
    ) {
      return true;
    }
  }
  return false;
}

function getTypeParametersFromTypeAlias(node) {
  if (isTypeAlias(node) && node.typeParameters && node.typeParameters.params) {
    return node.typeParameters.params;
  }
  return null;
}

function isTypeAlias(node) {
  return node.type === "TSTypeAliasDeclaration" || node.type === "TypeAlias";
}

function hasComplexTypeAnnotation(node) {
  if (node.type !== "VariableDeclarator") {
    return false;
  }
  const { typeAnnotation } = node.id;
  if (!typeAnnotation || !typeAnnotation.typeAnnotation) {
    return false;
  }
  const typeParams = getTypeParametersFromTypeReference(
    typeAnnotation.typeAnnotation
  );
  return (
    isNonEmptyArray(typeParams) &&
    typeParams.length > 1 &&
    typeParams.some(
      (param) =>
        isNonEmptyArray(getTypeParametersFromTypeReference(param)) ||
        param.type === "TSConditionalType"
    )
  );
}

function isArrowFunctionVariableDeclarator(node) {
  return (
    node.type === "VariableDeclarator" &&
    node.init &&
    node.init.type === "ArrowFunctionExpression"
  );
}

function getTypeParametersFromTypeReference(node) {
  if (
    isTypeReference(node) &&
    node.typeParameters &&
    node.typeParameters.params
  ) {
    return node.typeParameters.params;
  }
  return null;
}

function isTypeReference(node) {
  return (
    node.type === "TSTypeReference" || node.type === "GenericTypeAnnotation"
  );
}

/**
 * A chain with no calls at all or whose calls are all without arguments or with lone short arguments,
 * excluding chains printed by `printMemberChain`
 */
function isPoorlyBreakableMemberOrCallChain(
  path,
  options,
  print,
  deep = false
) {
  const node = path.getValue();
  const goDeeper = () =>
    isPoorlyBreakableMemberOrCallChain(path, options, print, true);

  if (node.type === "TSNonNullExpression") {
    return path.call(goDeeper, "expression");
  }

  if (isCallExpression(node)) {
    /** @type {any} TODO */
    const doc = printCallExpression(path, options, print);
    if (doc.label === "member-chain") {
      return false;
    }

    const args = getCallArguments(node);
    const isPoorlyBreakableCall =
      args.length === 0 ||
      (args.length === 1 && isLoneShortArgument(args[0], options));
    if (!isPoorlyBreakableCall) {
      return false;
    }

    if (isCallExpressionWithComplexTypeArguments(node, print)) {
      return false;
    }

    return path.call(goDeeper, "callee");
  }

  if (isMemberExpression(node)) {
    return path.call(goDeeper, "object");
  }

  return deep && (node.type === "Identifier" || node.type === "ThisExpression");
}

const LONE_SHORT_ARGUMENT_THRESHOLD_RATE = 0.25;

function isLoneShortArgument(node, { printWidth }) {
  if (hasComment(node)) {
    return false;
  }

  const threshold = printWidth * LONE_SHORT_ARGUMENT_THRESHOLD_RATE;

  if (
    node.type === "ThisExpression" ||
    (node.type === "Identifier" && node.name.length <= threshold) ||
    (isSignedNumericLiteral(node) && !hasComment(node.argument))
  ) {
    return true;
  }

  const regexpPattern =
    (node.type === "Literal" && "regex" in node && node.regex.pattern) ||
    (node.type === "RegExpLiteral" && node.pattern);

  if (regexpPattern) {
    return regexpPattern.length <= threshold;
  }

  if (isStringLiteral(node)) {
    return rawText(node).length <= threshold;
  }

  if (node.type === "TemplateLiteral") {
    return (
      node.expressions.length === 0 &&
      node.quasis[0].value.raw.length <= threshold &&
      !node.quasis[0].value.raw.includes("\n")
    );
  }

  return isLiteral(node);
}

function isObjectPropertyWithShortKey(node, keyDoc, options) {
  if (!isObjectProperty(node)) {
    return false;
  }
  // TODO: for performance, it might make sense to use a more lightweight
  // version of cleanDoc, such that it would stop once it detects that
  // the doc can't be reduced to a string.
  keyDoc = cleanDoc(keyDoc);
  const MIN_OVERLAP_FOR_BREAK = 3;
  //   ↓↓ - insufficient overlap for a line break
  // key1: longValue1,
  //   ↓↓↓↓↓↓ - overlap is long enough to break
  // key2abcd:
  //   longValue2
  return (
    typeof keyDoc === "string" &&
    getStringWidth(keyDoc) < options.tabWidth + MIN_OVERLAP_FOR_BREAK
  );
}

function isCallExpressionWithComplexTypeArguments(node, print) {
  const typeArgs = getTypeArgumentsFromCallExpression(node);
  if (isNonEmptyArray(typeArgs)) {
    if (typeArgs.length > 1) {
      return true;
    }
    if (typeArgs.length === 1) {
      const firstArg = typeArgs[0];
      if (
        firstArg.type === "TSUnionType" ||
        firstArg.type === "UnionTypeAnnotation" ||
        firstArg.type === "TSIntersectionType" ||
        firstArg.type === "IntersectionTypeAnnotation" ||
        firstArg.type === "TSTypeLiteral" ||
        firstArg.type === "ObjectTypeAnnotation"
      ) {
        return true;
      }
    }
    const typeArgsKeyName = node.typeParameters
      ? "typeParameters"
      : "typeArguments";
    if (willBreak(print(typeArgsKeyName))) {
      return true;
    }
  }
  return false;
}

function getTypeArgumentsFromCallExpression(node) {
  return (
    (node.typeParameters && node.typeParameters.params) ||
    (node.typeArguments && node.typeArguments.params)
  );
}

module.exports = {
  printVariableDeclarator,
  printAssignmentExpression,
  printAssignment,
  isArrowFunctionVariableDeclarator,
};