avoid infinite loop if package.xml is not found

[alsora]

The code in getPackageFromPluginXMLFilePath currently never exits from the while loop if the package.xml file is not found.
The reason is that the code assumes that parent_path() will eventually return an empty path, but this is not the case.
See source code for the function: https://github.com/ros2/rcpputils/blob/master/src/filesystem_helper.cpp#L172-L182

In the situation where the file is not found, the while loop will eventually reach the root of the filesystem and parent_path will continuously return the root itself.

This PR adds a check to make sure that we exit from the function if the path returned from parent_path is equal to the previous one.

Signed-off-by: Alberto Soragna alberto.soragna@gmail.com

[alsora]

@jacobperron @hidmic friendly ping

[jacobperron]

Thanks for the fix!

I think this was a bug introduced when switching to rcpputils post-Foxy.
In Foxy, pluginlib used it's own filesystem helper implementation:

pluginlib/pluginlib/include/pluginlib/class_loader_imp.hpp

Lines 620 to 632 in 0eb5308

	while (true) {
	if (pluginlib::impl::fs::exists(parent / "package.xml")) {
	std::string package_file_path = (parent / "package.xml").string();
	return extractPackageNameFromPackageXML(package_file_path);
	}
	// Recursive case - hop one folder up
	parent = parent.parent_path();
	// Base case - reached root and cannot find what we're looking for
	if (parent.string().empty()) {
	return "";
	}

which does return empty:

pluginlib/pluginlib/include/pluginlib/impl/filesystem_helper.hpp

Lines 138 to 142 in 0eb5308

	path parent("");
	for (auto it = this->cbegin(); it != --this->cend(); ++it) {
	parent /= *it;
	}
	return parent;

So we don't have to backport this to Foxy, but we should for Galactic.

CI:

• Linux
• Linux-aarch64
• macOS
• Windows

[cottsay]

@Mergifyio backport galactic

[mergify]

backport galactic

✅ Backports have been created

• #243 avoid infinite loop if package.xml is not found (backport #220) has been created for branch galactic