Consider targets with double colons to be IMPORTED or ALIAS targets.

Introduce a policy to control the behavior.

The AliasTargets unit test already tests that using a
double-semicolon in the name is not an error. Change the ExportImport
test to use a namespace with a double-semicolon too.

2 files changed, 24 insertions, 0 deletions

diff --git a/Help/manual/cmake-policies.7.rst b/Help/manual/cmake-policies.7.rst
index 658620f..f03cbe1 100644
--- a/Help/manual/cmake-policies.7.rst
+++ b/Help/manual/cmake-policies.7.rst
@@ -37,3 +37,4 @@ All Policies
    /policy/CMP0025
    /policy/CMP0026
    /policy/CMP0027
+   /policy/CMP0028
diff --git a/Help/policy/CMP0028.rst b/Help/policy/CMP0028.rst
new file mode 100644
index 0000000..ec318a0
--- /dev/null
+++ b/Help/policy/CMP0028.rst
@@ -0,0 +1,23 @@
+CMP0028
+-------
+
+Double colon in target name means ALIAS or IMPORTED target.
+
+CMake 2.8.12 and lower allowed the use of targets and files with double
+colons in target_link_libraries, with some buildsystem generators.
+
+The use of double-colons is a common pattern used to namespace IMPORTED
+targets and ALIAS targets.  When computing the link dependencies of a target,
+the name of each dependency could either be a target, or a file on disk.
+Previously, if a target was not found with a matching name, the name was
+considered to refer to a file on disk.  This can lead to confusing error
+messages if there is a typo in what should be a target name.
+
+The OLD behavior for this policy is to search for targets, then files on disk,
+even if the search term contains double-colons.  The NEW behavior for this
+policy is to issue a FATAL_ERROR if a link dependency contains
+double-colons but is not an IMPORTED target or an ALIAS target.
+
+This policy was introduced in CMake version 3.0.0.  CMake version
+|release| warns when the policy is not set and uses OLD behavior.  Use
+the cmake_policy command to set it to OLD or NEW explicitly.