Enable "strict" mode for runtime code.

[kitsonk]

We should be able to do this now.

Fixes #3324

[kitsonk]

Too many changes, will take another stab at this at some point in the future.

[Ciantic]

What do you mean by too many changes? I hope this makes it before 1.0, because that's when the libraries will start to gather speed.

[maxmellen]

@kitsonk Would you be open to contributions on this?

[kitsonk]

Too many changes upstream, making it difficult to land the PR.

Yeah, @maxmellen, if you wanted to try.

[maxmellen]

Great! Having a go at it.

I noticed these compiler options moved to compiler_host.ts where there are now multiple sets of compiler options:

deno/cli/js/compiler_host.ts

Lines 33 to 73 in ed68055

	/** Options that need to be used when generating a bundle (either trusted or
	* runtime). */
	export const defaultBundlerOptions: ts.CompilerOptions = {
	inlineSourceMap: false,
	module: ts.ModuleKind.AMD,
	outDir: undefined,
	outFile: `${OUT_DIR}/bundle.js`,
	// disabled until we have effective way to modify source maps
	sourceMap: false
	};
	/** Default options used by the compiler Host when compiling. */
	export const defaultCompileOptions: ts.CompilerOptions = {
	allowJs: true,
	allowNonTsExtensions: true,
	// TODO(#3324) Enable strict mode for user code.
	// strict: true,
	checkJs: false,
	esModuleInterop: true,
	module: ts.ModuleKind.ESNext,
	outDir: OUT_DIR,
	resolveJsonModule: true,
	sourceMap: true,
	stripComments: true,
	target: ts.ScriptTarget.ESNext,
	jsx: ts.JsxEmit.React
	};
	/** Options that need to be used when doing a runtime (non bundled) compilation */
	export const defaultRuntimeCompileOptions: ts.CompilerOptions = {
	outDir: undefined
	};
	/** Default options used when doing a transpile only. */
	export const defaultTranspileOptions: ts.CompilerOptions = {
	esModuleInterop: true,
	module: ts.ModuleKind.ESNext,
	sourceMap: true,
	scriptComments: true,
	target: ts.ScriptTarget.ESNext
	};

I was wondering if strict mode should also be enabled in these other options, notably the defaultTranspileOptions.

@kitsonk What do you think?

[maxmellen]

@kitsonk I've opened a PR here: #3899

[kitsonk]

Transpile does no type checking, so strict mode makes no sense there.