ts-docs.ts

const ts = require("typescript");
const vfs = require("@typescript/vfs");

const compilerOptions = {
  strict: true,
  target: ts.ScriptTarget.ES2015,
  typeRoots: [],
  lib: ["es5"],
  skipDefaultLibCheck: true,
  skipLibCheck: true,
  moduleResolution: ts.ModuleResolutionKind.NodeJs,
  module: ts.ModuleKind.ES2015,
};

const filename = "index.ts";
const file = `
interface StackBaseProps<T> {
  as: T;
  hasWrap?: boolean;
}

interface StackJustifyProps {
  /** The foo prop should not repeat the description */
  foo?: 'blue';
  /** You cannot use gap when using a "space" justify property */
  gap?: never;
}

interface StackGapProps {
  /** The foo prop should not repeat the description */
  foo?: 'red';
  /** The space between children */
  gap?: number;
}

type StackProps<T = string> = StackBaseProps<T> & (StackGapProps | StackJustifyProps);
`;

async function run() {
  const fsMap = await vfs.createDefaultMapFromNodeModules(compilerOptions);
  fsMap.set(filename, file);

  const system = vfs.createSystem(fsMap);
  const host = vfs.createVirtualCompilerHost(system, compilerOptions, ts);
  const program = ts.createProgram({
    rootNames: [...fsMap.keys()],
    options: compilerOptions,
    host: host.compilerHost,
  });
  const checker = program.getTypeChecker();

  // This will update the fsMap with new files
  // for the .d.ts and .js files
  program.emit();

  // Now I can look at the AST for the .ts file too
  const index = program.getSourceFile("index.ts");

  const properties = checker
    .getDeclaredTypeOfSymbol(index.locals.get("StackProps"))
    .getProperties();

  console.log(
    properties.map((prop) => {
      const propType = checker.getTypeOfSymbolAtLocation(prop, index);
      const isOptional = (prop.getFlags() & ts.SymbolFlags.Optional) !== 0;
      const description = Array.from(
        new Set(
          prop
            .getDocumentationComment()
            .map((d) => d.text.trim())
            .filter((t) => t !== "")
        )
      ).join("\n");

      return {
        name: prop.getName(),
        type: checker.typeToString(propType),
        // BUG: Required always returns true
        required: !isOptional,
        description,
      };
    })
  );
}

run();