Fix GH#18217 issue for FileLog.

[valera-rozuvan]

Fixes occurrence of #18217 in FileLog class.

[ghost]

The only reason this removes the need for a cast is because we don't have "strictPropertyInitialization": true, set in tsconfig-base.json -- if that were set then there would be an error at private readonly logFile: string;. As it is currently you've fooled the compiler into thinking logFile can't be undefined, when it actually can since it's only assigned conditionally in the constructor -- but the error will come back when we enable strictPropertyInitialization.

I think a simpler fix would be to just add if (this.logEnabled && this.logFile !== undefined) { ... } around the body of writeLine -- so far it's worked because callers checked isEnabled() first, but it would actually be simpler and safer if they didn't and just called writeLine unconditionally and let us handle everything in there. @sheetalkamat thoughts?

[sheetalkamat]

I think keeping isEnabled is good idea since we don't want to create potential string concats if not necessary. It would be good idea to assert isEnabled instead?

[ghost]

Maybe we could generate the string lazily? writeLine(getText: () => string)

[sheetalkamat]

If done that way, it needs to create unnecessary function expresions.

[valera-rozuvan]

@Andy-MS

I have updated this PR. Now the parameter to logFile constructor has explicit type string | undefined. No need for conditional if on every call of writeLine. Please check ;)

[ghost]

I think it would be better if logEnabled was just rolled into the optionality of logFile -- if the log is enabled logFile should be set, otherwise logFile will be undefined. Then we don't have to initialize logFile with a value it should never actually use.

[valera-rozuvan]

@Andy-MS I updated the PR, didn't see your last comment at first.

If I got your last comment correct, you think that we should use logFile property as a means to figure out if the instance of the class is enabled or not? If it's undefined, then the instance is disabled. Otherwise, it is a string, and we can proceed to try writing the file. If we get an error, we set logFile to undefined, and next time we can bail out. RIght?

Or do you like the current state of my proposed changes?

[ghost]

Right.

[valera-rozuvan]

@Andy-MS Updated PR.