fix: handle anonymous callsites. (fixes #5)

[jordrake]

Fixes #5 by ensuring we only call path.basename on callsites with a valid file path. The find below should act as a filter of these falsy (usually null from what I've seen) values.

In the unlikely case that there is no suitable file path, set the filename as unknown.

[klaudiosinani]

By replacing the lines 65-66 of signale.js with the following:

// signale.js 
// ...
const callers = stack.map(x => x.getFileName()); // L65
console.log(callers); // L66
// ...

and then running example of #5 on both node 8.9.1 and 9.11.1:

// file path: home/signale/foo.js
const signale = require('signale');
signale.config({displayFilename: true});

Promise.resolve().then(() => {
  signale.error('Foo');
});

we get these file paths, returned by the callsites:

// Filepaths returned by callsites
[ 'home/signale/foo.js',
  'home/signale/foo.js',
  'home/signale/foo.js',
  'home/signale/foo.js',
  'home/signale/foo.js',
  'home/signale/foo.js',
  null,
  'internal/process/next_tick.js',
  'module.js',
  'bootstrap_node.js' ]

Thus, the issue is indeed path.basename(x.getFileName()), that crushes once null, returned by the <anonymous> callsite, is pass to it as an argument. So, instead of returning unknown, we can still return the filename foo.js just by calling path.basename at the end of filename(), e.g:

  get filename() {
    const _ = Error.prepareStackTrace;
    Error.prepareStackTrace = (error, stack) => stack;
    const {stack} = new Error();
    Error.prepareStackTrace = _;

    const callers = stack.map(x => x.getFileName()); // Remove path.basename()

    const filePath = callers.find(x => {  // Get the whole filepath
      return x !== callers[0];
    });

    return path.basename(filePath);  // Return the basename
  }

It is an initial idea, so please feel free to share your thoughts : )

[jordrake]

The unknown case was to handle a scenario where we had so many anonymous call-sites that it pushed any sensible filename past the callsite limit (default I believe is 10) where get filename would have a stack trace like:

Error
    at Signale.get filename [as filename] (/mnt/d/dev/signale/signale.js:65:17)
    at Signale._formatFilename (/mnt/d/dev/signale/signale.js:100:21)
    at Signale._meta (/mnt/d/dev/signale/signale.js:124:22)
    at Signale._buildSignale (/mnt/d/dev/signale/signale.js:151:26)
    at Signale._logger (/mnt/d/dev/signale/signale.js:82:20)
    at <anonymous>
    at <anonymous>
	at <anonymous>
	at <anonymous>
    at <anonymous>
	at <anonymous>
	at <anonymous>
    at <anonymous>
	at <anonymous>

I've not actually managed to create this scenario mind you. Happy to remove it.

[klaudiosinani]

I completely agree, we can then change the return statement to something like this:

return firstExternalFilePath ? path.basename(firstExternalFilePath) : 'anonymous';

This way even the most extreme cases can be covered and also avoid any potential errors on the way

[klaudiosinani]

Original comment: #30 (comment)

return firstExternalFilePath ? path.basename(firstExternalFilePath) : 'anonymous';

[klaudiosinani]

Awesome! Thank you a lot : )