Likewise, maybe in our PerfLogger wrapper, we could have a logInfoEventIf<T extends any[]>(condition: boolean, logText: (...args: T) => string, ...args: T), so we can avoid introducing control flow statements for logging into code not related to the logging?

I'm not sure I understand this suggestion.

Rather than

if (etwLogger && result && result.resolvedModule) etwLogger.logInfoEvent(`Module "${moduleName}" resolved to "${result.resolvedModule.resolvedFileName}"`)

write

logger.logInfoEventIf(result && result.resolvedModule, (moduleName, result) => `Module "${moduleName}" resolved to "${result.resolvedModule.resolvedFileName}"`, moduleName, result);

like how our ts.Debug.assert signature is setup. (This way the control flow for the logger is within the logger and if the message isn't logged, the string isn't calculated)

How is that preferable?

It moves the control flow for the conditional-ness of the logging into the logger, so anyone reading the implementation doesn't need to reason over the effects of the control flow that's only there for the logger. The function-instead-of-string bit is just an optimization to avoid doing expensive string building (like typeToString) if the branch isn't hit - it's not strictly needed, and is why ts.Debug.assert takes both a string and a function argument.

I considered the second suggestion (moving conditional logic inside the logger class), but that is very unwieldy given the strong typing that is currently in place. We would need logInfoEventIf(), logStartCommandIf(), logStopCommandIf(), etc... It seems like overkill for this problem.

Here's a version using a fluent API to avoid remaking conditional methods with similar definitions (you could construct the passthru instance reflectively, but eh):

usage:

perfLogger.if(moduleResolution).logEvent("message");

I tried this out but it's still missing the piece where the message is a function instead of a string. Without that the string interpolation could fail with a null reference.

At this point I'd like to move forward with the code that I have which is pretty straightforward and has addressed all of the other comments. What do you think @sheetalkamat ?

You can redefine if to be

        if(condition: boolean, cb: (logger: PerfLogger) => void): void {
          if (condition) {
            return cb(this.base);
          }
        }

with usage

perfLogger.if(moduleResolution, log => log.logEvent("message"));

if that's the concern.