Get .d.ts from input path

getDeclaration.ts

/**
 * @prompt
 * 指定されたTypeScriptのファイルから型定義とimportを抽出します
 * $ deno run -A getDeclaration.ts <target>
 */

import ts from "npm:[email protected]";

export function getSourceSummary(filePath: string): string {
  const compilerOptions: ts.CompilerOptions = {
    declaration: true,
    emitDeclarationOnly: true,
    noEmitOnError: false,
    target: ts.ScriptTarget.ESNext,
    module: ts.ModuleKind.ESNext,
    removeComments: false,
    moduleResolution: ts.ModuleResolutionKind.NodeNext,
    skipLibCheck: true,
    allowJs: true,
    checkJs: false,
    strict: false,
    noImplicitAny: false,
  };

  const host = ts.createCompilerHost(compilerOptions);
  let declarationOutput = "";
  host.writeFile = (fileName, contents) => {
    if (fileName.endsWith(".d.ts")) {
      declarationOutput = contents;
    }
  };

  const program = ts.createProgram({
    rootNames: [filePath],
    options: compilerOptions,
    host: host,
  });
  program.emit();
  const source = program.getSourceFile(filePath)!;
  const imports = source.statements.filter((stmt) =>
    ts.isImportDeclaration(stmt)
  );
  const printer = ts.createPrinter({
    removeComments: true,
  });
  let outputText = "";
  if (imports.length > 0) {
    outputText += "/// Imports\n";
  }
  for (const stmt of imports) {
    const importCode = printer.printNode(ts.EmitHint.Unspecified, stmt, source);
    outputText += importCode + "\n";
  }

  outputText += `/// Declaration\n${declarationOutput}`;
  return outputText;
}

if (import.meta.main) {
  const filePath = Deno.args[0];
  const summary = getSourceSummary(filePath);
  console.log(summary);
}