Option to fail on warnings

[l1bbcsg]

I would like to propose an option that could make the compiler fail if at least one warning is encountered, regardless of errors and exit with a non-zero exit code.

This could be a simple flags such as --fail-on-warnings or a more sophisticated setting like --error-level that could introduce more granular control, i.e. still exit with 0 if compilation failed with errors.

Use case for this is either a purist approach when no warnings are tolerated or code quality control CI job that verifies new code with --checks-only.

[brad4d]

I believe this option already exists. The magic words are --jscomp_error=* to say "treat all diagnostic groups as errors".

[l1bbcsg]

I don't think this is quite the right option. It seems to change behaviour much more elevating a lot of other warnings that are not normally reported to errors.

This example:

/**
 * @type {number}
 */
let a = 10;

a = 'foo'

Produces a warning:

google-closure-compiler a.js --checks_only --warning_level verbose

a.js:6: WARNING - [JSC_TYPE_MISMATCH] assignment
found   : string
required: number
a = 'foo'
^^^^^^^^^

0 error(s), 1 warning(s), 100.0% typed

But with --jscomp_error=* there are now two errors:

google-closure-compiler a.js --checks_only --warning_level verbose --jscomp_error=*

a.js:6: ERROR - [JSC_MISSING_SEMICOLON] Missing semicolon
a = 'foo'
^^^^^^^^^

a.js:6: ERROR - [JSC_TYPE_MISMATCH] assignment
found   : string
required: number
a = 'foo'
^^^^^^^^^

2 error(s), 0 warning(s), 100.0% typed

On a large code base I encountered many more new errors and compiler actually crashed with java.lang.RuntimeException: INTERNAL COMPILER ERROR.

[brad4d]

Created internal issue
http://b/139437890

[brad4d]

This is looking harder to do than I'd wish, but I think the gist is that the proposed option would need to trigger doing options.addWarningsGuard(new StrictWarningsGuard()) when the compiler options are created in CommandLineRunner#createOptions().