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Restore builtins.pathExists behavior on broken symlinks

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Commit 83c067c0fa changed `builtins.pathExists`
to resolve symlinks before checking for existence. Consequently, if the path
refers to a symlink itself, existence of the target of the symlink (instead of
the symlink itself) was checked. Restore the previous behavior by skipping
symlink resolution in the last component.
This commit is contained in:
Alois Wohlschlager 2024-02-10 20:56:54 +01:00
parent 28a988bdde
commit 89e21ab4bd
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GPG key ID: E0F59EA5E5216914
5 changed files with 46 additions and 19 deletions
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22
src/libutil/source-path.cc
View file

@ -62,7 +62,7 @@ bool SourcePath::operator<(const SourcePath & x) const
return std::tie(*accessor, path) < std::tie(*x.accessor, x.path);
}
SourcePath SourcePath::resolveSymlinks() const
SourcePath SourcePath::resolveSymlinks(SymlinkResolution mode) const
{
auto res = SourcePath(accessor);
@ -72,6 +72,8 @@ SourcePath SourcePath::resolveSymlinks() const
for (auto & c : path)
todo.push_back(std::string(c));
bool resolve_last = mode == SymlinkResolution::Full;
while (!todo.empty()) {
auto c = *todo.begin();
todo.pop_front();
@ -81,14 +83,16 @@ SourcePath SourcePath::resolveSymlinks() const
res.path.pop();
else {
res.path.push(c);
if (auto st = res.maybeLstat(); st && st->type == InputAccessor::tSymlink) {
if (!linksAllowed--)
throw Error("infinite symlink recursion in path '%s'", path);
auto target = res.readLink();
res.path.pop();
if (hasPrefix(target, "/"))
res.path = CanonPath::root;
todo.splice(todo.begin(), tokenizeString<std::list<std::string>>(target, "/"));
if (resolve_last || !todo.empty()) {
if (auto st = res.maybeLstat(); st && st->type == InputAccessor::tSymlink) {
if (!linksAllowed--)
throw Error("infinite symlink recursion in path '%s'", path);
auto target = res.readLink();
res.path.pop();
if (hasPrefix(target, "/"))
res.path = CanonPath::root;
todo.splice(todo.begin(), tokenizeString<std::list<std::string>>(target, "/"));
}
}
}
}

24
src/libutil/source-path.hh
View file

@ -11,6 +11,22 @@
namespace nix {
enum class SymlinkResolution {
/**
* Resolve symlinks in the ancestors only.
*
* Only the last component of the result is possibly a symlink.
*/
Ancestors,
/**
* Resolve symlinks fully, realpath(3)-style.
*
* No component of the result will be a symlink.
*/
Full,
};
/**
* An abstraction for accessing source files during
* evaluation. Currently, it's just a wrapper around `CanonPath` that
@ -103,11 +119,11 @@ struct SourcePath
bool operator<(const SourcePath & x) const;
/**
* Resolve any symlinks in this `SourcePath` (including its
* parents). The result is a `SourcePath` in which no element is a
* symlink.
* Resolve any symlinks in this `SourcePath` according to the
* given resolution mode.
*/
SourcePath resolveSymlinks() const;
SourcePath resolveSymlinks(
SymlinkResolution mode = SymlinkResolution::Full) const;
};
std::ostream & operator << (std::ostream & str, const SourcePath & path);