member-delimiter-style.ts

import { TSESLint, TSESTree, AST_NODE_TYPES } from '@typescript-eslint/utils';
import * as util from '../util';

type Delimiter = 'comma' | 'none' | 'semi';
// need type's implicit index sig for deepMerge
// eslint-disable-next-line @typescript-eslint/consistent-type-definitions
type TypeOptions = {
  delimiter?: Delimiter;
  requireLast?: boolean;
};
type TypeOptionsWithType = TypeOptions & {
  type: string;
};
// eslint-disable-next-line @typescript-eslint/consistent-type-definitions
type BaseOptions = {
  multiline?: TypeOptions;
  singleline?: TypeOptions;
};
type Config = BaseOptions & {
  overrides?: {
    typeLiteral?: BaseOptions;
    interface?: BaseOptions;
  };
  multilineDetection?: 'brackets' | 'last-member';
};
type Options = [Config];
type MessageIds =
  | 'unexpectedComma'
  | 'unexpectedSemi'
  | 'expectedComma'
  | 'expectedSemi';
type LastTokenType = TSESTree.Token;

interface MakeFixFunctionParams {
  optsNone: boolean;
  optsSemi: boolean;
  lastToken: LastTokenType;
  missingDelimiter: boolean;
  lastTokenLine: string;
  isSingleLine: boolean;
}

type MakeFixFunctionReturnType =
  | ((fixer: TSESLint.RuleFixer) => TSESLint.RuleFix)
  | null;

const definition = {
  type: 'object',
  properties: {
    multiline: {
      type: 'object',
      properties: {
        delimiter: { enum: ['none', 'semi', 'comma'] },
        requireLast: { type: 'boolean' },
      },
      additionalProperties: false,
    },
    singleline: {
      type: 'object',
      properties: {
        // note can't have "none" for single line delimiter as it's invalid syntax
        delimiter: { enum: ['semi', 'comma'] },
        requireLast: { type: 'boolean' },
      },
      additionalProperties: false,
    },
  },
  additionalProperties: false,
};

const isLastTokenEndOfLine = (token: LastTokenType, line: string): boolean => {
  const positionInLine = token.loc.start.column;

  return positionInLine === line.length - 1;
};

const makeFixFunction = ({
  optsNone,
  optsSemi,
  lastToken,
  missingDelimiter,
  lastTokenLine,
  isSingleLine,
}: MakeFixFunctionParams): MakeFixFunctionReturnType => {
  // if removing is the action but last token is not the end of the line
  if (
    optsNone &&
    !isLastTokenEndOfLine(lastToken, lastTokenLine) &&
    !isSingleLine
  ) {
    return null;
  }

  return (fixer: TSESLint.RuleFixer): TSESLint.RuleFix => {
    if (optsNone) {
      // remove the unneeded token
      return fixer.remove(lastToken);
    }

    const token = optsSemi ? ';' : ',';

    if (missingDelimiter) {
      // add the missing delimiter
      return fixer.insertTextAfter(lastToken, token);
    }

    // correct the current delimiter
    return fixer.replaceText(lastToken, token);
  };
};

export default util.createRule<Options, MessageIds>({
  name: 'member-delimiter-style',
  meta: {
    type: 'suggestion',
    docs: {
      description:
        'Require a specific member delimiter style for interfaces and type literals',
      recommended: false,
    },
    fixable: 'code',
    messages: {
      unexpectedComma: 'Unexpected separator (,).',
      unexpectedSemi: 'Unexpected separator (;).',
      expectedComma: 'Expected a comma.',
      expectedSemi: 'Expected a semicolon.',
    },
    schema: [
      {
        type: 'object',
        properties: Object.assign({}, definition.properties, {
          overrides: {
            type: 'object',
            properties: {
              interface: definition,
              typeLiteral: definition,
            },
            additionalProperties: false,
          },
          multilineDetection: {
            enum: ['brackets', 'last-member'],
          },
        }),
        additionalProperties: false,
      },
    ],
  },
  defaultOptions: [
    {
      multiline: {
        delimiter: 'semi',
        requireLast: true,
      },
      singleline: {
        delimiter: 'semi',
        requireLast: false,
      },
      multilineDetection: 'brackets',
    },
  ],
  create(context, [options]) {
    const sourceCode = context.getSourceCode();

    // use the base options as the defaults for the cases
    const baseOptions = options;
    const overrides = baseOptions.overrides ?? {};
    const interfaceOptions: BaseOptions = util.deepMerge(
      baseOptions,
      overrides.interface,
    );
    const typeLiteralOptions: BaseOptions = util.deepMerge(
      baseOptions,
      overrides.typeLiteral,
    );

    /**
     * Check the last token in the given member.
     * @param member the member to be evaluated.
     * @param opts the options to be validated.
     * @param isLast a flag indicating `member` is the last in the interface or type literal.
     */
    function checkLastToken(
      member: TSESTree.TypeElement,
      opts: TypeOptionsWithType,
      isLast: boolean,
    ): void {
      /**
       * Resolves the boolean value for the given setting enum value
       * @param type the option name
       */
      function getOption(type: Delimiter): boolean {
        if (isLast && !opts.requireLast) {
          // only turn the option on if its expecting no delimiter for the last member
          return type === 'none';
        }
        return opts.delimiter === type;
      }

      let messageId: MessageIds | null = null;
      let missingDelimiter = false;
      const lastToken = sourceCode.getLastToken(member, {
        includeComments: false,
      });

      if (!lastToken) {
        return;
      }

      const sourceCodeLines = sourceCode.getLines();
      const lastTokenLine = sourceCodeLines[lastToken?.loc.start.line - 1];

      const optsSemi = getOption('semi');
      const optsComma = getOption('comma');
      const optsNone = getOption('none');

      if (lastToken.value === ';') {
        if (optsComma) {
          messageId = 'expectedComma';
        } else if (optsNone) {
          missingDelimiter = true;
          messageId = 'unexpectedSemi';
        }
      } else if (lastToken.value === ',') {
        if (optsSemi) {
          messageId = 'expectedSemi';
        } else if (optsNone) {
          missingDelimiter = true;
          messageId = 'unexpectedComma';
        }
      } else {
        if (optsSemi) {
          missingDelimiter = true;
          messageId = 'expectedSemi';
        } else if (optsComma) {
          missingDelimiter = true;
          messageId = 'expectedComma';
        }
      }

      if (messageId) {
        context.report({
          node: lastToken,
          loc: {
            start: {
              line: lastToken.loc.end.line,
              column: lastToken.loc.end.column,
            },
            end: {
              line: lastToken.loc.end.line,
              column: lastToken.loc.end.column,
            },
          },
          messageId,
          fix: makeFixFunction({
            optsNone,
            optsSemi,
            lastToken,
            missingDelimiter,
            lastTokenLine,
            isSingleLine: opts.type === 'single-line',
          }),
        });
      }
    }

    /**
     * Check the member separator being used matches the delimiter.
     * @param {ASTNode} node the node to be evaluated.
     */
    function checkMemberSeparatorStyle(
      node: TSESTree.TSInterfaceBody | TSESTree.TSTypeLiteral,
    ): void {
      const members =
        node.type === AST_NODE_TYPES.TSInterfaceBody ? node.body : node.members;

      let isSingleLine = node.loc.start.line === node.loc.end.line;
      if (
        options.multilineDetection === 'last-member' &&
        !isSingleLine &&
        members.length > 0
      ) {
        const lastMember = members[members.length - 1];
        if (lastMember.loc.end.line === node.loc.end.line) {
          isSingleLine = true;
        }
      }

      const typeOpts =
        node.type === AST_NODE_TYPES.TSInterfaceBody
          ? interfaceOptions
          : typeLiteralOptions;
      const opts = isSingleLine
        ? { ...typeOpts.singleline, type: 'single-line' }
        : { ...typeOpts.multiline, type: 'multi-line' };

      members.forEach((member, index) => {
        checkLastToken(member, opts ?? {}, index === members.length - 1);
      });
    }

    return {
      TSInterfaceBody: checkMemberSeparatorStyle,
      TSTypeLiteral: checkMemberSeparatorStyle,
    };
  },
});