Base reporter, add unified diff separator

[olsonpm]

Right now the unified diff output has no separators. Resulting in output similar to this:

Having not used mocha in some time, I had completely forgotten it splits before/after 4 lines from the affected text and spent a while trying to figure out how "PD" could possibly be having values of "15/30" or "50/100".

I don't know what kind of separator to add, but a blank line or two should suffice for majority of cases. I'd have to check to see if other libraries have tackled this problem how they went about it.

The code to modify would be this:

mocha/lib/reporters/base.js

Lines 161 to 207 in 7493bca

	failures.forEach(function(test, i){
	// format
	var fmt = color('error title', ' %s) %s:\n')
	+ color('error message', ' %s')
	+ color('error stack', '\n%s\n');
	// msg
	var err = test.err
	, message = err.message || ''
	, stack = err.stack || message
	, index = stack.indexOf(message)
	, actual = err.actual
	, expected = err.expected
	, escape = true;
	if (index === -1) {
	msg = message;
	} else {
	index += message.length;
	msg = stack.slice(0, index);
	// remove msg from stack
	stack = stack.slice(index + 1);
	}
	// uncaught
	if (err.uncaught) {
	msg = 'Uncaught ' + msg;
	}
	// explicitly show diff
	if (err.showDiff !== false && sameType(actual, expected)
	&& expected !== undefined) {
	escape = false;
	if (!(utils.isString(actual) && utils.isString(expected))) {
	err.actual = actual = utils.stringify(actual);
	err.expected = expected = utils.stringify(expected);
	}
	fmt = color('error title', ' %s) %s:\n%s') + color('error stack', '\n%s\n');
	var match = message.match(/^([^:]+): expected/);
	msg = '\n ' + color('error message', match ? match[1] : msg);
	if (exports.inlineDiffs) {
	msg += inlineDiff(err, escape);
	} else {
	msg += unifiedDiff(err, escape);
	}
	}

[ScottFreeCode]

Git has a format something like this: @@ -<line number of start of this segment in previous file version>,<number of lines removed> +<line number of start of this segment in next file version>,<number of lines added> @@
It's blue, where the + are green and the - are red. And I'm not sure I'm interpreting those numbers exactly right -- maybe the numbers after the commas include the unchanged lines shown?

[olsonpm]

hmm - the problem with generating line numbers is that these diffs are for formatted objects, thus line numbers don't seem appropriate.

However I did notice git grep separates sections with \n--\n if multiple matches are found. That seems intuitive enough.

Edit: especially if they were colored something beside green/red

[boneskull]

@olsonpm Can you show what should be output?

[olsonpm]

As I said I'm open for discussion on what makes the most sense, but my vote leans toward the output of git grep -C<number>, where sections are delimited by a double dash. E.g.

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[olsonpm]

@boneskull - trying to prevent the issue from being closed. I provided the requested feedback, so at least remove that label please.

[ScottFreeCode]

I'd be fine with just -- as a separator if no one has better suggestions or other concerns. Do we want to put this behind a flag for compatibility? (Another advantage to a flag would be we could provide the ability to override -- with some other non-dynamic string...)

[boneskull]

unexpected may have a good solution we can pilfer; let's take a look at what their messaging looks like.

Otherwise, -- is just as reasonable as any other string.

@ScottFreeCode I don't think this needs an option to change the separator, and a flag also feels like overkill.

If we're erring on the site of caution, this is semver-major, because it could confuse anything that's programmatically consuming the output. No, nothing should consume it, but something probably does.