add_dependencies: Allow calling with no dependencies

Fixes: #26713

Help/command/add_dependencies.rst

@@ -12,7 +12,6 @@ ensure that they build before ``<target>`` does.  A top-level target
 is one created by one of the :command:`add_executable`,
 :command:`add_library`, or :command:`add_custom_target` commands
 (but not targets generated by CMake like ``install``).
-At least one ``<target-dependency>`` must be given.
 
 Dependencies added to an :ref:`imported target <Imported Targets>`
 or an :ref:`interface library <Interface Libraries>` are followed
@@ -32,6 +31,10 @@ transitively in its place since the target itself does not build.
   finished before sources in ``<target>`` start compiling; this
   ensures generated sources are available.
 
+.. versionchanged:: 4.1
+  The command may be called with no dependencies.
+  Previously, at least one dependency was required.
+
 See Also
 ^^^^^^^^
 

Help/release/dev/add-dependency-one-arg.rst

@@ -0,0 +1,4 @@
+add-dependency-one-arg
+----------------------
+
+* The :command:`add_dependencies` command may be called with no dependencies.

Source/cmAddDependenciesCommand.cxx

@@ -12,7 +12,7 @@
 bool cmAddDependenciesCommand(std::vector<std::string> const& args,
                               cmExecutionStatus& status)
 {
-  if (args.size() < 2) {
+  if (args.empty()) {
     status.SetError("called with incorrect number of arguments");
     return false;
   }

Tests/RunCMake/add_dependencies/NoArgs-result.txt

@@ -0,0 +1 @@
+1

Tests/RunCMake/add_dependencies/NoArgs-stderr.txt

@@ -0,0 +1,4 @@
+CMake Error at NoArgs.cmake:[0-9]+ \(add_dependencies\):
+  add_dependencies called with incorrect number of arguments
+Call Stack \(most recent call first\):
+  CMakeLists\.txt:[0-9]+ \(include\)

Tests/RunCMake/add_dependencies/NoArgs.cmake

@@ -0,0 +1 @@
+add_dependencies()

Tests/RunCMake/add_dependencies/NoDependencies.cmake

@@ -0,0 +1,3 @@
+enable_language(C)
+add_library(a a.c)
+add_dependencies(a ${noDependencies})

Tests/RunCMake/add_dependencies/RunCMakeTest.cmake

@@ -1,5 +1,7 @@
 include(RunCMake)
 
+run_cmake(NoArgs)
 run_cmake(NoTarget)
+run_cmake(NoDependencies)
 run_cmake(ReadOnlyProperty)
 run_cmake(RetrieveDependencies)