Reduce amount of code necessary to quickly format the diagnostics to a string

Search Terms

FormatDiagnosticsHost

Suggestion

Often when someone is working with the TypeScript compiler API their type checker might have diagnostics. It would be useful for people to quickly check them by typing:

ts.formatDiagnostics(ts.getPreEmitDiagnostics(program))

Instead of:

ts.formatDiagnostics(ts.getPreEmitDiagnostics(program), {
    getCurrentDirectory: () => ts.sys.getCurrentDirectory(),
    getCanonicalFileName: f => f,
    getNewLine: () => "\n"
})

Possible solution is to make providing FormatDiagnosticsHost optional or add a default FormatDiagnosticsHost that people can use (or both).

Also for ts.formatDiagnostic and ts.formatDiagnosticsWithColorAndContext

Use Cases

Easier for people to quickly check the diagnostics while they're developing with the compiler API.

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

Related Issues

#29581

Start with the TypeScript compiler API entry points formatDiagnostics, formatDiagnostic, and formatDiagnosticsWithColorAndContext, then trace how FormatDiagnosticsHost is currently required. Compare the proposed optional-host and default-host approaches, while preserving existing calls. Done means diagnostics can be quickly formatted without passing a host, with existing behavior unchanged.