[cmake-developers] [CMake 0015681]: add_custom_command(TARGET ...) can't see in scope target

[Mantis Bug Tracker]

The following issue has been SUBMITTED. 
====================================================================== 
http://www.cmake.org/Bug/view.php?id=15681 
====================================================================== 
Reported By:                Dan Liew
Assigned To:                
====================================================================== 
Project:                    CMake
Issue ID:                   15681
Category:                   CMake
Reproducibility:            always
Severity:                   major
Priority:                   normal
Status:                     new
====================================================================== 
Date Submitted:             2015-08-04 17:18 EDT
Last Modified:              2015-08-04 17:18 EDT
====================================================================== 
Summary:                    add_custom_command(TARGET ...) can't see in scope
target
Description: 
'm observing a problem with CMake's add_custom_command() when using
the TARGET version of the signature.

Code demonstrating the issue can be found at [1]

In ``test/CMakeLists.txt`` [2] I try using add_custom_command() to
build and run an executable every time the ``foolib`` library is
rebuilt. The motivation behind doing this is to have some very quick
and simple library tests run every time the library is built.

This use of add_custom_command() does not seem to work at all.

Using CMake 2.8.12.2 the requested command is not invoked when running
``make foolib``. I am aware that the custom command won't run if
``foolib`` has already been made but even if I do a clean build the
custom command specified does not run.

When using CMake 3.2.3 I get a warning about CMP0040 which complains
that the target passed to the TARGET argument in
``add_custom_command()`` doesn't exist.

```
  Policy CMP0040 is not set: The target in the TARGET signature of
  add_custom_command() must exist.  Run "cmake --help-policy CMP0040" for
  policy details.  Use the cmake_policy command to set the policy and
  suppress this warning.

  The target name "foolib" is unknown in this context.
This warning is for project developers.  Use -Wno-dev to suppress it
```


This doesn't make sense the target **clearly exists and is in scope**
because the ``simple_test`` executable links against it and also it is
possible to read properties of the target.

Seems like there's some sort of weird scope issue going on here.


[1] https://github.com/delcypher/cmake_add_custom_command_bug
[2]
https://github.com/delcypher/cmake_add_custom_command_bug/blob/master/test/CMakeLists.txt


Steps to Reproduce: 
$ git clone https://github.com/delcypher/cmake_add_custom_command_bug.git
$ cd cmake_add_custom_command_bug
$ mkdir build
$ cd build
# Under new versions of CMake a warning is emitted about the "foolib" target not
being known in this context
$ cmake ../

$ make foolib VERBOSE=1

you will see that none of the custom commands are executed
====================================================================== 

Issue History 
Date Modified    Username       Field                    Change               
====================================================================== 
2015-08-04 17:18 Dan Liew       New Issue                                    
======================================================================