target_link_libraries: Optionally require only target names

Optionally verify that items in `LINK_LIBRARIES` and
`INTERFACE_LINK_LIBRARIES` that can be target names are actually target
names.  Add a `LINK_LIBRARIES_ONLY_TARGETS` target property and
corresponding `CMAKE_LINK_LIBRARIES_ONLY_TARGETS` variable to enable
this new check.

Fixes: #22858

3 files changed, 53 insertions, 0 deletions

diff --git a/Source/cmGeneratorTarget.cxx b/Source/cmGeneratorTarget.cxx
index 0036e69..b651104 100644
--- a/Source/cmGeneratorTarget.cxx
+++ b/Source/cmGeneratorTarget.cxx
@@ -6247,6 +6247,18 @@ cmComputeLinkInformation* cmGeneratorTarget::GetLinkInformation(
 
 void cmGeneratorTarget::CheckLinkLibraries() const
 {
+  bool linkLibrariesOnlyTargets =
+    this->GetPropertyAsBool("LINK_LIBRARIES_ONLY_TARGETS");
+
+  // Evaluate the link interface of this target if needed for extra checks.
+  if (linkLibrariesOnlyTargets) {
+    std::vector<std::string> const& configs =
+      this->Makefile->GetGeneratorConfigs(cmMakefile::IncludeEmptyConfig);
+    for (std::string const& config : configs) {
+      this->GetLinkInterfaceLibraries(config, this, LinkInterfaceFor::Link);
+    }
+  }
+
   // Check link the implementation for each generated configuration.
   for (auto const& hmp : this->LinkImplMap) {
     HeadToLinkImplementationMap const& hm = hmp.second;
@@ -6260,6 +6272,10 @@ void cmGeneratorTarget::CheckLinkLibraries() const
       if (!this->VerifyLinkItemColons(LinkItemRole::Implementation, item)) {
         return;
       }
+      if (linkLibrariesOnlyTargets &&
+          !this->VerifyLinkItemIsTarget(LinkItemRole::Implementation, item)) {
+        return;
+      }
     }
   }
 
@@ -6276,6 +6292,10 @@ void cmGeneratorTarget::CheckLinkLibraries() const
         if (!this->VerifyLinkItemColons(LinkItemRole::Interface, item)) {
           return;
         }
+        if (linkLibrariesOnlyTargets &&
+            !this->VerifyLinkItemIsTarget(LinkItemRole::Interface, item)) {
+          return;
+        }
       }
     }
   }
@@ -6329,6 +6349,35 @@ bool cmGeneratorTarget::VerifyLinkItemColons(LinkItemRole role,
   return false;
 }
 
+bool cmGeneratorTarget::VerifyLinkItemIsTarget(LinkItemRole role,
+                                               cmLinkItem const& item) const
+{
+  if (item.Target) {
+    return true;
+  }
+  std::string const& str = item.AsStr();
+  if (!str.empty() &&
+      (str[0] == '-' || str[0] == '$' || str[0] == '`' ||
+       str.find_first_of("/\\") != std::string::npos)) {
+    return true;
+  }
+
+  std::string e = cmStrCat("Target \"", this->GetName(),
+                           "\" has LINK_LIBRARIES_ONLY_TARGETS enabled, but ",
+                           role == LinkItemRole::Implementation
+                             ? "it links to"
+                             : "its link interface contains",
+                           ":\n  ", item.AsStr(), "\nwhich is not a target.  ",
+                           missingTargetPossibleReasons);
+  cmListFileBacktrace backtrace = item.Backtrace;
+  if (backtrace.Empty()) {
+    backtrace = this->GetBacktrace();
+  }
+  this->LocalGenerator->GetCMakeInstance()->IssueMessage(
+    MessageType::FATAL_ERROR, e, backtrace);
+  return false;
+}
+
 void cmGeneratorTarget::GetTargetVersion(int& major, int& minor) const
 {
   int patch;
diff --git a/Source/cmGeneratorTarget.h b/Source/cmGeneratorTarget.h
index 096e2ea..5f317c4 100644
--- a/Source/cmGeneratorTarget.h
+++ b/Source/cmGeneratorTarget.h
@@ -982,6 +982,7 @@ private:
     Implementation,
     Interface,
   };
+  bool VerifyLinkItemIsTarget(LinkItemRole role, cmLinkItem const& item) const;
   bool VerifyLinkItemColons(LinkItemRole role, cmLinkItem const& item) const;
 
   // Cache import information from properties for each configuration.
diff --git a/Source/cmTarget.cxx b/Source/cmTarget.cxx
index 38361cc..c03a252 100644
--- a/Source/cmTarget.cxx
+++ b/Source/cmTarget.cxx
@@ -471,6 +471,9 @@ cmTarget::cmTarget(std::string const& name, cmStateEnums::TargetType type,
         initProp(property);
       }
     }
+    if (!this->IsImported()) {
+      initProp("LINK_LIBRARIES_ONLY_TARGETS");
+    }
   }
 
   // Save the backtrace of target construction.