src: prefer C++ empty() in boolean expressions

[tniessen]

This changes occurrences of length() and size() to empty() where it makes the code simpler.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

[gengjiawen]

Maybe also add readability-container-size-empty to https://github.com/nodejs/node/blob/a42dcbeb43ab22c0db07c4e0a9eab5e0f44578f4/src/.clang-tidy.

[bnoordhuis]

Wildly inefficient way of removing empty prefixes... (n reallocations + n*m copies when 1 + m suffices)

Suggested change

	while (url->path.size() > 1 && url->path[0].empty()) {
	url->path.erase(url->path.begin());
	}
	auto begin = url->path.begin();
	auto end = url->path.end();
	auto from = begin;
	auto to = begin;
	while (to != end && to->empty()) ++to;
	if (to == end && from == begin && from != to) ++from;
	url->path.erase(from, to); // 1 + m

[addaleax]

@bnoordhuis In your suggestion, the from == begin part is always true, unless i’m missing something?

[bnoordhuis]

Sorry, yeah. It was intended as a kind of self-documentation about the preconditions but I guess it's confusing more than anything else. if (to == end && from != end) ++from; is probably a clearer way of writing it.

[jasnell]

As this is not directly related to the other changes in this PR, this could be done in a separate commit/PR.

[devsnek]

the future is now

[gengjiawen]

Failed test case in macOS. is this a flaky test ? cc @Trott

Path: parallel/test-macos-app-sandbox
--- stderr ---
assert.js:103
  throw new AssertionError(obj);
  ^

AssertionError [ERR_ASSERTION]: Expected values to be strictly equal:

1 !== 0

    at Object.<anonymous> (/Users/runner/work/node/node/test/parallel/test-macos-app-sandbox.js:41:8)
    at Module._compile (internal/modules/cjs/loader.js:1252:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1273:10)
    at Module.load (internal/modules/cjs/loader.js:1101:32)
    at Function.Module._load (internal/modules/cjs/loader.js:966:14)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:60:12)
    at internal/main/run_main_module.js:17:47 {
  generatedMessage: true,
  code: 'ERR_ASSERTION',
  actual: 1,
  expected: 0,
  operator: 'strictEqual'
}

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/32699/

[jasnell]

Landed in 1be7bbd