function goUnionType()

in internal/lsp/protocol/typescript/code.ts [861:979]

• 97 lines of code
• 57 McCabe index (conditional complexity)

function goUnionType(n: ts.UnionTypeNode, nm: string): string {
  let help = `/*${n.getText()}*/`;  // show the original as a comment
  // There are some bad cases with newlines:
  // range?: boolean | {\n	};
  // full?: boolean | {\n		/**\n		 * The server supports deltas for full documents.\n		 */\n		delta?: boolean;\n	}
  // These are handled specially:
  if (nm == 'range') help = help.replace(/\n/, '');
  if (nm == 'full' && help.indexOf('\n') != -1) {
    help = '/*boolean | <elided struct>*/';
  }
  // handle all the special cases
  switch (n.types.length) {
    case 2: {
      const a = strKind(n.types[0]);
      const b = strKind(n.types[1]);
      if (a == 'NumberKeyword' && b == 'StringKeyword') {  // ID
        return `interface{} ${help}`;
      }
      // for null, b is not useful (LiternalType)
      if (n.types[1].getText() === 'null') {
        if (nm == 'textDocument/codeAction') {
          // (Command | CodeAction)[] | null
          return `[]CodeAction ${help}`;
        }
        let v = goType(n.types[0], 'a');
        return `${v} ${help}`;
      }
      if (a == 'BooleanKeyword') {  // usually want bool
        if (nm == 'codeActionProvider') return `interface{} ${help}`;
        if (nm == 'renameProvider') return `interface{} ${help}`;
        if (nm == 'full') return `interface{} ${help}`; // there's a struct
        if (nm == 'save') return `${goType(n.types[1], '680')} ${help}`;
        return `${goType(n.types[0], 'b')} ${help}`;
      }
      if (b == 'ArrayType') return `${goType(n.types[1], 'c')} ${help}`;
      if (help.includes('InsertReplaceEdit') && n.types[0].getText() == 'TextEdit') {
        return `*TextEdit ${help}`;
      }
      if (a == 'TypeReference') {
        if (nm == 'edits') return `${goType(n.types[0], '901')} ${help}`;
        if (a == b) return `interface{} ${help}`;
        if (nm == 'code') return `interface{} ${help}`;
        if (nm == 'editRange') return `${goType(n.types[0], '904')} ${help}`;
        if (nm === 'location') return `${goType(n.types[0], '905')} ${help}`;
      }
      if (a == 'StringKeyword') return `string ${help}`;
      if (a == 'TypeLiteral' && nm == 'TextDocumentContentChangeEvent') {
        return `${goType(n.types[0], nm)}`;
      }
      if (a == 'TypeLiteral' && b === 'TypeLiteral') {
        // DocumentDiagnosticReport
        // the first one includes the second one
        return `${goType(n.types[0], '9d')}`;
      }
      throw new Error(`911 ${nm}: a:${a}/${goType(n.types[0], '9a')} b:${b}/${goType(n.types[1], '9b')} ${loc(n)}`);
    }
    case 3: {
      const aa = strKind(n.types[0]);
      const bb = strKind(n.types[1]);
      const cc = strKind(n.types[2]);
      if (nm === 'workspace/symbol') return `${goType(n.types[0], '930')} ${help}`;
      if (nm == 'DocumentFilter' || nm == 'NotebookDocumentFilter' || nm == 'TextDocumentFilter') {
        // not really a union. the first is enough, up to a missing
        // omitempty but avoid repetitious comments
        return `${goType(n.types[0], 'g')}`;
      }
      if (nm == 'textDocument/documentSymbol') {
        return `[]interface{} ${help}`;
      }
      if (aa == 'TypeReference' && bb == 'ArrayType' && (cc == 'NullKeyword' || cc === 'LiteralType')) {
        return `${goType(n.types[0], 'd')} ${help}`;
      }
      if (aa == 'TypeReference' && bb == aa && cc == 'ArrayType') {
        // should check that this is Hover.Contents
        return `${goType(n.types[0], 'e')} ${help}`;
      }
      if (aa == 'ArrayType' && bb == 'TypeReference' && (cc == 'NullKeyword' || cc === 'LiteralType')) {
        // check this is nm == 'textDocument/completion'
        return `${goType(n.types[1], 'f')} ${help}`;
      }
      if (aa == 'LiteralType' && bb == aa && cc == aa) return `string ${help}`;
      // keep this for diagnosing unexpected interface{} results
      // console.log(`931, interface{} for ${aa}/${goType(n.types[0], 'g')},${bb}/${goType(n.types[1], 'h')},${cc}/${goType(n.types[2], 'i')} ${nm}`);
      break;
    }
    case 4:
      if (nm == 'documentChanges') return `TextDocumentEdit ${help} `;
      if (nm == 'textDocument/prepareRename') return `Range ${help} `;
      break;
    case 8: // LSPany
      break;
    default:
      throw new Error(`957 goUnionType len=${n.types.length} nm=${nm} ${n.getText()}`);
  }

  // Result will be interface{} with a comment
  let isLiteral = true;
  let literal = 'string';
  let res = 'interface{} /* ';
  n.types.forEach((v: ts.TypeNode, i: number) => {
    // might get an interface inside:
    //  (Command | CodeAction)[] | null
    let m = goType(v, nm);
    if (m.indexOf('interface') != -1) {
      // avoid nested comments
      m = m.split(' ')[0];
    }
    m = m.split('\n').join('; ');  // sloppy: struct{;
    res = res.concat(`${i == 0 ? '' : ' | '}`, m);
    if (!ts.isLiteralTypeNode(v)) isLiteral = false;
    else literal = strKind(v.literal) == 'StringLiteral' ? 'string' : 'number';
  });
  if (!isLiteral) {
    return res + '*/';
  }
  // I don't think we get here
  // trace?: 'off' | 'messages' | 'verbose' should get string
  return `${literal} /* ${n.getText()} */`;
}