cmake_path(IS_PREFIX) and $<PATH:IS_PREFIX> treated an empty path as a
prefix of every path, including another empty path, following
std::filesystem::path. A prefix that is empty because a variable was
set to an empty value, or because a generator expression argument
expanded to nothing, therefore satisfied a check meant to reject it.
Return false for an empty prefix, in cmCMakePath::IsPrefix so that every
caller shares one implementation and both the plain and NORMALIZE forms
are covered. Normalizing an empty path leaves it empty, so no separate
handling of NORMALIZE is needed. Unlike the component comparison, which
follows std::filesystem::path deliberately, IsPrefix has no counterpart
in the standard: it borrows path iteration but the predicate itself is
defined by CMake, so an empty prefix is a gap to fill rather than a
standard answer to override.
Add policy CMP0223 and restore the old result behind it at the two
released surfaces. The other callers of IsPrefix, source_group() and
the Makefile generator's source classification, take the new behavior
ungated: source_group() rejects an empty TREE argument before reaching
it, and the generator passes the source and binary directories.
The if(PATH_IS_PREFIX) operator, new in this same release, follows the
policy too rather than simply taking the new behavior, so that it agrees
with cmake_path(IS_PREFIX) in every policy state and the parity
assertions in its test hold unconditionally.
Fixes: #28077
Add explicit cross-references for commands which optionally take an
output variable (otherwise modifying their input in-place) for clarity.
Note that `cmake_path` should not be used to modify variables reserved
by CMake.
Improve references to the "CMake-style" semicolon-separated lists, and
apply those corresponding changes to the `file` command page.
Using `signature` renders the anchor links for each sub-command, and is
consistent with the other `Help/command` pages which contain multiple
sub-commands.
Indenting a list relative to the previous paragraph creates
a blockquote. Combined with the natural list indent it results
in an overly large left margin.
The docs for if(PATH_EQUAL) did not mention the component-wise
nature of the checks. It also claimed no normalization was
performed, but multiple separators are effectively collapsed
(part of normalization). Improve the wording to clarify both of
these points.
Also update the corresponding description of cmake_path(COMPARE),
which had the same inaccuracy.
Fixes: #23758
Fix a typo accidentally added by commit eb583b0a66 (cmake_path command:
path management, 2020-07-23). Remove a stray `]` character that breaks
the pygments lexer.
Mickaël Germain
Brad King
Tyler Yankee
xndcn
Nikita Nemkin
Juan Ramos
Alex Turbov
Craig Scott
Marc Chevrier
Michael Hirsch