V8 engine support

[PopGoesTheWza]

Fixes #735

• npm run test succeeds.
• npm run lint succeeds.
• Appropriate changes to README are included in PR.

[PopGoesTheWza]

@shinout : please review & test this PR

if OK, we'll ask grant for a release

[shinout]

All your changes seem good to me 👍

One thing I would like to request is that the getTranspileOptions() in files.ts should use ts.findConfigFile(). Otherwise, tsconfig files cannot be found in monorepo-structured projects.

function getTranspileOptions(): ts.TranspileOptions {
  const projectPath = findUp.sync(DOT.PROJECT.PATH);
  const tsconfigPath = projectPath
    ? ts.findConfigFile(projectPath, ts.sys.fileExists)
    : undefined;
  if (!tsconfigPath) {
    return {};
  }
  const tsconfigContent = fs.readFileSync(tsconfigPath, FS_OPTIONS);
  const parsedConfigResult = ts.parseConfigFileTextToJson(
    tsconfigPath,
    tsconfigContent
  );
  return {
    compilerOptions: parsedConfigResult.config.compilerOptions
  };
}

This may work.

[shinout]

@PopGoesTheWza
Also, I have to say that I failed to push ESNext codes to GAS even using this branch of clasp. As I repeatedly said, it's because of GAS server which parses pushed codes as non-ESNext ones. I think it's too early to release this version until GAS accepts ESNext codes via HTTP. Have you ever encountered a similar situation?

[PopGoesTheWza]

Otherwise, tsconfig files cannot be found in monorepo-structured projects.

@shinout do you have a sample monorepo to test?

I personally use this template for single repo/multiple GAS targets. I plan on updating it to support V8 engine.

[PopGoesTheWza]

until GAS accepts ESNext codes via HTTP

@shinout I am unsure what you mean. I had no time for testing clasp push of ES2019 yet but intend to do so this weekend.

[shinout]

@PopGoesTheWza
Here is a sample monorepo directory structure.
This is the most typical one when using lerna.

(monorepo root)
├── tsconfig.json
├── packages
│   └── gas-package01
│       └── index.ts

The essence is that the main directory (gas-package01 here) is two or more directories distant from tsconfig.json. The current implementation only considers the parent directory of a given project. ts. findConfigFile() looks up ancestors recursively.
https://github.com/microsoft/TypeScript/blob/4a34294908bed6701dcba2456ca7ac5eafe0ddff/src/compiler/program.ts#L4

I am unsure what you mean

Sorry about that. Let me explain more precisely. The command clasp push uses googleapis's method projects.updateContent(). It accesses to this REST API, which seems to validate pushed codes before updating contents. The validation fails when we push ESNext codes, then the update cannot be done. I suppose the validation logic at their REST API server still doesn't accept ESNext grammar. Thus, even if this version of clasp is released, we won't be able to push ESNext codes.

[PopGoesTheWza]

@grant ready for release.

I drafted the release notes https://github.com/google/clasp/releases/edit/untagged-477cea24e1e150fb3fc4