type-annotation-spacing.ts

import type { TSESTree } from '@typescript-eslint/utils';

import {
  createRule,
  isClassOrTypeElement,
  isFunction,
  isFunctionOrFunctionType,
  isIdentifier,
  isTSConstructorType,
  isTSFunctionType,
  isVariableDeclarator,
} from '../util';

interface WhitespaceRule {
  readonly before?: boolean;
  readonly after?: boolean;
}

interface WhitespaceOverride {
  readonly colon?: WhitespaceRule;
  readonly arrow?: WhitespaceRule;
  readonly variable?: WhitespaceRule;
  readonly property?: WhitespaceRule;
  readonly parameter?: WhitespaceRule;
  readonly returnType?: WhitespaceRule;
}

interface Config extends WhitespaceRule {
  readonly overrides?: WhitespaceOverride;
}

type WhitespaceRules = Required<WhitespaceOverride>;

type Options = [Config?];
type MessageIds =
  | 'expectedSpaceAfter'
  | 'expectedSpaceBefore'
  | 'unexpectedSpaceAfter'
  | 'unexpectedSpaceBefore'
  | 'unexpectedSpaceBetween';

function createRules(options?: Config): WhitespaceRules {
  const globals = {
    ...(options?.before !== undefined ? { before: options.before } : {}),
    ...(options?.after !== undefined ? { after: options.after } : {}),
  };
  const override = options?.overrides ?? {};
  const colon = {
    ...{ before: false, after: true },
    ...globals,
    ...override?.colon,
  };
  const arrow = {
    ...{ before: true, after: true },
    ...globals,
    ...override?.arrow,
  };

  return {
    colon: colon,
    arrow: arrow,
    variable: { ...colon, ...override?.variable },
    property: { ...colon, ...override?.property },
    parameter: { ...colon, ...override?.parameter },
    returnType: { ...colon, ...override?.returnType },
  };
}

function getIdentifierRules(
  rules: WhitespaceRules,
  node: TSESTree.Node | undefined,
): WhitespaceRule {
  const scope = node?.parent;

  if (isVariableDeclarator(scope)) {
    return rules.variable;
  } else if (isFunctionOrFunctionType(scope)) {
    return rules.parameter;
  }
  return rules.colon;
}

function getRules(
  rules: WhitespaceRules,
  node: TSESTree.TypeNode,
): WhitespaceRule {
  const scope = node?.parent?.parent;

  if (isTSFunctionType(scope) || isTSConstructorType(scope)) {
    return rules.arrow;
  } else if (isIdentifier(scope)) {
    return getIdentifierRules(rules, scope);
  } else if (isClassOrTypeElement(scope)) {
    return rules.property;
  } else if (isFunction(scope)) {
    return rules.returnType;
  }
  return rules.colon;
}

export default createRule<Options, MessageIds>({
  name: 'type-annotation-spacing',
  meta: {
    type: 'layout',
    docs: {
      description: 'Require consistent spacing around type annotations',
    },
    fixable: 'whitespace',
    messages: {
      expectedSpaceAfter: "Expected a space after the '{{type}}'.",
      expectedSpaceBefore: "Expected a space before the '{{type}}'.",
      unexpectedSpaceAfter: "Unexpected space after the '{{type}}'.",
      unexpectedSpaceBefore: "Unexpected space before the '{{type}}'.",
      unexpectedSpaceBetween:
        "Unexpected space between the '{{previousToken}}' and the '{{type}}'.",
    },
    schema: [
      {
        $defs: {
          spacingConfig: {
            type: 'object',
            properties: {
              before: { type: 'boolean' },
              after: { type: 'boolean' },
            },
            additionalProperties: false,
          },
        },
        type: 'object',
        properties: {
          before: { type: 'boolean' },
          after: { type: 'boolean' },
          overrides: {
            type: 'object',
            properties: {
              colon: { $ref: '#/items/0/$defs/spacingConfig' },
              arrow: { $ref: '#/items/0/$defs/spacingConfig' },
              variable: { $ref: '#/items/0/$defs/spacingConfig' },
              parameter: { $ref: '#/items/0/$defs/spacingConfig' },
              property: { $ref: '#/items/0/$defs/spacingConfig' },
              returnType: { $ref: '#/items/0/$defs/spacingConfig' },
            },
            additionalProperties: false,
          },
        },
        additionalProperties: false,
      },
    ],
  },
  defaultOptions: [
    // technically there is a default, but the overrides mean
    // that if we apply them here, it will break the no override case.
    {},
  ],
  create(context, [options]) {
    const punctuators = [':', '=>'];
    const sourceCode = context.getSourceCode();

    const ruleSet = createRules(options);

    /**
     * Checks if there's proper spacing around type annotations (no space
     * before colon, one space after).
     */
    function checkTypeAnnotationSpacing(
      typeAnnotation: TSESTree.TypeNode,
    ): void {
      const nextToken = typeAnnotation;
      const punctuatorTokenEnd = sourceCode.getTokenBefore(nextToken)!;
      let punctuatorTokenStart = punctuatorTokenEnd;
      let previousToken = sourceCode.getTokenBefore(punctuatorTokenEnd)!;
      let type = punctuatorTokenEnd.value;

      if (!punctuators.includes(type)) {
        return;
      }

      const { before, after } = getRules(ruleSet, typeAnnotation);

      if (type === ':' && previousToken.value === '?') {
        if (
          // eslint-disable-next-line deprecation/deprecation -- TODO - switch once our min ESLint version is 6.7.0
          sourceCode.isSpaceBetweenTokens(previousToken, punctuatorTokenStart)
        ) {
          context.report({
            node: punctuatorTokenStart,
            messageId: 'unexpectedSpaceBetween',
            data: {
              type,
              previousToken: previousToken.value,
            },
            fix(fixer) {
              return fixer.removeRange([
                previousToken.range[1],
                punctuatorTokenStart.range[0],
              ]);
            },
          });
        }

        // shift the start to the ?
        type = '?:';
        punctuatorTokenStart = previousToken;
        previousToken = sourceCode.getTokenBefore(previousToken)!;

        // handle the +/- modifiers for optional modification operators
        if (previousToken.value === '+' || previousToken.value === '-') {
          type = `${previousToken.value}?:`;
          punctuatorTokenStart = previousToken;
          previousToken = sourceCode.getTokenBefore(previousToken)!;
        }
      }

      const previousDelta =
        punctuatorTokenStart.range[0] - previousToken.range[1];
      const nextDelta = nextToken.range[0] - punctuatorTokenEnd.range[1];

      if (after && nextDelta === 0) {
        context.report({
          node: punctuatorTokenEnd,
          messageId: 'expectedSpaceAfter',
          data: {
            type,
          },
          fix(fixer) {
            return fixer.insertTextAfter(punctuatorTokenEnd, ' ');
          },
        });
      } else if (!after && nextDelta > 0) {
        context.report({
          node: punctuatorTokenEnd,
          messageId: 'unexpectedSpaceAfter',
          data: {
            type,
          },
          fix(fixer) {
            return fixer.removeRange([
              punctuatorTokenEnd.range[1],
              nextToken.range[0],
            ]);
          },
        });
      }

      if (before && previousDelta === 0) {
        context.report({
          node: punctuatorTokenStart,
          messageId: 'expectedSpaceBefore',
          data: {
            type,
          },
          fix(fixer) {
            return fixer.insertTextAfter(previousToken, ' ');
          },
        });
      } else if (!before && previousDelta > 0) {
        context.report({
          node: punctuatorTokenStart,
          messageId: 'unexpectedSpaceBefore',
          data: {
            type,
          },
          fix(fixer) {
            return fixer.removeRange([
              previousToken.range[1],
              punctuatorTokenStart.range[0],
            ]);
          },
        });
      }
    }

    return {
      TSMappedType(node): void {
        if (node.typeAnnotation) {
          checkTypeAnnotationSpacing(node.typeAnnotation);
        }
      },
      TSTypeAnnotation(node): void {
        checkTypeAnnotationSpacing(node.typeAnnotation);
      },
    };
  },
});