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Mickaël Germain
860583ceac
Testing whether one path is a prefix of another is possible today with
cmake_path(IS_PREFIX), but the idiom needs a separate statement plus a
scratch variable and takes the prefix as a variable name, so projects
reach for if(path MATCHES "^${prefix}") instead. That is wrong whenever
the prefix contains a regex metacharacter, and it accepts siblings,
because '^/a/b' matches '/a/bc'.
Add a binary operator where the left operand is the candidate prefix and
the right is the path, matching the operand order of cmake_path(IS_PREFIX)
and $<PATH:IS_PREFIX> so that the same operation reads the same way on all
three surfaces. Neither operand is normalized, matching the default of
cmake_path(IS_PREFIX) and the existing PATH_EQUAL operator, so '.' and
'..' are compared as ordinary components. The test is non-strict, purely
lexical, and applies no relative-to-absolute reconciliation.
Add policy CMP0222 for compatibility, modeled on CMP0139. The keyword
is consumed as an operator only when it appears in the second argument
slot, so a variable named PATH_IS_PREFIX keeps working in unary and
left-operand position. What the policy covers is such a variable
appearing after another token, as in if(NOT PATH_IS_PREFIX AND other),
which becomes a configure error under NEW.
Since the operator is an if() spelling of cmake_path(IS_PREFIX) and shares
its implementation, test it by asserting the two agree over a corpus of
inputs rather than by restating expected values. Those are pinned by the
cmake_path(IS_PREFIX) test, so the operator's tests stay limited to what
has no command equivalent, and no platform branching is needed because
parity holds whatever the host path model answers.
Fixes: #28040
14 lines
546 B
CMake
14 lines
546 B
CMake
cmake_policy(SET CMP0222 NEW)
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# Under NEW the keyword is interpreted as an operator and evaluated. The
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# operator's own behavior is covered by the RunCMake.if PathIsPrefix case,
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# which outlives this directory: the OLD and WARN cases here are removed
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# once support for the OLD behavior is dropped.
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if(NOT "/a/b" PATH_IS_PREFIX "/a/b/c")
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message(SEND_ERROR "if(PATH_IS_PREFIX): '/a/b' not a prefix of '/a/b/c'")
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endif()
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if("/a/b" PATH_IS_PREFIX "/a/bc")
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message(SEND_ERROR "if(PATH_IS_PREFIX): '/a/b' wrongly a prefix of '/a/bc'")
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endif()
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