CMP0022: Plain target_link_libraries must populate link interface

The CMP0022 NEW behavior is that the INTERFACE_LINK_LIBRARIES property
exactly defines the link interface.  The plain target_link_libraries
signature says linking is transitive by default, so it should populate
the property.

Teach the target_link_libraries plain signature to populate the
INTERFACE_LINK_LIBRARIES regardless of the CMP0022 setting.  Refactor
the cmTarget::ComputeLinkInterface checks that warn when the policy is
not set to compare the new property to either the explicitly set old
link interface properties or the link implementation fallback for all
linkable target types, not just static libraries.

This fixes a regression in 2.8.12.0 that caused target_link_libraries to
not implement transitive linking in the plain signature once the policy
CMP0022 is set to NEW.

4 files changed, 122 insertions, 140 deletions

diff --git a/Source/cmExportFileGenerator.cxx b/Source/cmExportFileGenerator.cxx
index ef336ea..a30c5e4 100644
--- a/Source/cmExportFileGenerator.cxx
+++ b/Source/cmExportFileGenerator.cxx
@@ -631,6 +631,7 @@ cmExportFileGenerator
 
   if (iface->ImplementationIsInterface)
     {
+    // Policy CMP0022 must not be NEW.
     this->SetImportLinkProperty(suffix, target,
                                 "IMPORTED_LINK_INTERFACE_LIBRARIES",
                                 iface->Libraries, properties, missingTargets);
diff --git a/Source/cmTarget.cxx b/Source/cmTarget.cxx
index 779b239..3365caf 100644
--- a/Source/cmTarget.cxx
+++ b/Source/cmTarget.cxx
@@ -2331,21 +2331,10 @@ void cmTarget::MergeLinkLibraries( cmMakefile& mf,
   i += this->PrevLinkedLibraries.size();
   for( ; i != libs.end(); ++i )
     {
-    const char *lib = i->first.c_str();
-    // We call this so that the dependencies get written to the cache
-    this->AddLinkLibrary( mf, selfname, lib, i->second );
-
-    if (this->GetType() == cmTarget::STATIC_LIBRARY)
-      {
-      std::string configLib = this->GetDebugGeneratorExpressions(lib,
-                                                                 i->second);
-      if (cmGeneratorExpression::IsValidTargetName(lib)
-          || cmGeneratorExpression::Find(lib) != std::string::npos)
-        {
-        configLib = "$<LINK_ONLY:" + configLib + ">";
-        }
-        this->AppendProperty("INTERFACE_LINK_LIBRARIES", configLib.c_str());
-      }
+    // This is equivalent to the target_link_libraries plain signature.
+    this->AddLinkLibrary( mf, selfname, i->first.c_str(), i->second );
+    this->AppendProperty("INTERFACE_LINK_LIBRARIES",
+      this->GetDebugGeneratorExpressions(i->first.c_str(), i->second).c_str());
     }
   this->PrevLinkedLibraries = libs;
 }
@@ -6417,12 +6406,20 @@ bool cmTarget::ComputeLinkInterface(const char* config, LinkInterface& iface,
   // An explicit list of interface libraries may be set for shared
   // libraries and executables that export symbols.
   const char* explicitLibraries = 0;
-  const char* newExplicitLibraries =
-                                this->GetProperty("INTERFACE_LINK_LIBRARIES");
   std::string linkIfaceProp;
-  if(this->GetType() == cmTarget::SHARED_LIBRARY ||
-     this->IsExecutableWithExports())
+  if(this->PolicyStatusCMP0022 != cmPolicies::OLD &&
+     this->PolicyStatusCMP0022 != cmPolicies::WARN)
     {
+    // CMP0022 NEW behavior is to use INTERFACE_LINK_LIBRARIES.
+    linkIfaceProp = "INTERFACE_LINK_LIBRARIES";
+    explicitLibraries = this->GetProperty(linkIfaceProp.c_str());
+    }
+  else if(this->GetType() == cmTarget::SHARED_LIBRARY ||
+          this->IsExecutableWithExports())
+    {
+    // CMP0022 OLD behavior is to use LINK_INTERFACE_LIBRARIES if set on a
+    // shared lib or executable.
+
     // Lookup the per-configuration property.
     linkIfaceProp = "LINK_INTERFACE_LIBRARIES";
     linkIfaceProp += suffix;
@@ -6434,120 +6431,30 @@ bool cmTarget::ComputeLinkInterface(const char* config, LinkInterface& iface,
       linkIfaceProp = "LINK_INTERFACE_LIBRARIES";
       explicitLibraries = this->GetProperty(linkIfaceProp.c_str());
       }
-    if (newExplicitLibraries
-        && (!explicitLibraries ||
-            (explicitLibraries
-              && strcmp(newExplicitLibraries, explicitLibraries) != 0)))
-      {
-      switch(this->GetPolicyStatusCMP0022())
-        {
-        case cmPolicies::WARN:
-          {
-          cmOStringStream w;
-          w << (this->Makefile->GetPolicies()
-                ->GetPolicyWarning(cmPolicies::CMP0022)) << "\n"
-            << "Target \"" << this->GetName() << "\" has a "
-              "INTERFACE_LINK_LIBRARIES property which differs from its "
-            << linkIfaceProp << " properties."
-              "\n"
-              "INTERFACE_LINK_LIBRARIES:\n  "
-            << newExplicitLibraries
-            << "\n"
-            << linkIfaceProp << ":\n  "
-            << (explicitLibraries ? explicitLibraries : "(empty)") << "\n";
-          this->Makefile->IssueMessage(cmake::AUTHOR_WARNING, w.str());
-          }
-          // Fall through
-        case cmPolicies::OLD:
-          break;
-        case cmPolicies::REQUIRED_IF_USED:
-        case cmPolicies::REQUIRED_ALWAYS:
-        case cmPolicies::NEW:
-          explicitLibraries = newExplicitLibraries;
-          linkIfaceProp = "INTERFACE_LINK_LIBRARIES";
-          break;
-        }
-      }
     }
-  else if(this->GetType() == cmTarget::STATIC_LIBRARY)
+
+  if(explicitLibraries && this->PolicyStatusCMP0022 == cmPolicies::WARN)
     {
-    if (newExplicitLibraries)
+    // Compare the explicitly set old link interface properties to the
+    // preferred new link interface property one and warn if different.
+    const char* newExplicitLibraries =
+      this->GetProperty("INTERFACE_LINK_LIBRARIES");
+    if (newExplicitLibraries
+        && strcmp(newExplicitLibraries, explicitLibraries) != 0)
       {
-      cmListFileBacktrace lfbt;
-      cmGeneratorExpression ge(lfbt);
-      cmGeneratorExpressionDAGChecker dagChecker(lfbt, this->GetName(),
-                                            "INTERFACE_LINK_LIBRARIES", 0, 0);
-      std::vector<std::string> ifaceLibs;
-      cmSystemTools::ExpandListArgument(
-          ge.Parse(newExplicitLibraries)->Evaluate(
-                                          this->Makefile,
-                                          config,
-                                          false,
-                                          headTarget,
-                                          this, &dagChecker), ifaceLibs);
-      LinkImplementation const* impl = this->GetLinkImplementation(config,
-                                                                headTarget);
-      if (ifaceLibs != impl->Libraries)
-        {
-        switch(this->GetPolicyStatusCMP0022())
-          {
-          case cmPolicies::WARN:
-            {
-            std::string oldLibraries;
-            std::string newLibraries;
-            const char *sep = "";
-            for(std::vector<std::string>::const_iterator it
-                = impl->Libraries.begin(); it != impl->Libraries.end(); ++it)
-              {
-              oldLibraries += sep;
-              oldLibraries += *it;
-              sep = ";";
-              }
-            sep = "";
-            for(std::vector<std::string>::const_iterator it
-                = ifaceLibs.begin(); it != ifaceLibs.end(); ++it)
-              {
-              newLibraries += sep;
-              newLibraries += *it;
-              sep = ";";
-              }
-
-            cmOStringStream w;
-            w << (this->Makefile->GetPolicies()
-                  ->GetPolicyWarning(cmPolicies::CMP0022)) << "\n"
-              << "Static library target \"" << this->GetName() << "\" has a "
-                "INTERFACE_LINK_LIBRARIES property.  This should be preferred "
-                "as the source of the link interface for this library.  "
-                "Ignoring the property and using the link implementation "
-                "as the link interface instead."
-                "\n"
-                "INTERFACE_LINK_LIBRARIES:\n  "
-              << newLibraries
-              << "\n"
-              << "Link implementation:\n  "
-              << oldLibraries << "\n";
-            this->Makefile->IssueMessage(cmake::AUTHOR_WARNING, w.str());
-            }
-            // Fall through
-          case cmPolicies::OLD:
-            break;
-          case cmPolicies::REQUIRED_IF_USED:
-          case cmPolicies::REQUIRED_ALWAYS:
-          case cmPolicies::NEW:
-            explicitLibraries = newExplicitLibraries;
-            linkIfaceProp = "INTERFACE_LINK_LIBRARIES";
-            break;
-          }
-        }
-      else
-        {
-        iface.Libraries = impl->Libraries;
-        if(this->LinkLanguagePropagatesToDependents())
-          {
-          // Targets using this archive need its language runtime libraries.
-          iface.Languages = impl->Languages;
-          }
-        }
+      cmOStringStream w;
+      w <<
+        (this->Makefile->GetPolicies()
+         ->GetPolicyWarning(cmPolicies::CMP0022)) << "\n"
+        "Target \"" << this->GetName() << "\" has an "
+        "INTERFACE_LINK_LIBRARIES property which differs from its " <<
+        linkIfaceProp << " properties."
+        "\n"
+        "INTERFACE_LINK_LIBRARIES:\n"
+        "  " << newExplicitLibraries << "\n" <<
+        linkIfaceProp << ":\n"
+        "  " << (explicitLibraries ? explicitLibraries : "(empty)") << "\n";
+      this->Makefile->IssueMessage(cmake::AUTHOR_WARNING, w.str());
       }
     }
 
@@ -6618,11 +6525,12 @@ bool cmTarget::ComputeLinkInterface(const char* config, LinkInterface& iface,
         }
       }
     }
-  else if (this->GetPolicyStatusCMP0022() == cmPolicies::WARN
-        || this->GetPolicyStatusCMP0022() == cmPolicies::OLD)
-    // The implementation shouldn't be the interface if CMP0022 is NEW. That
-    // way, the LINK_LIBRARIES property can be set directly without having to
-    // empty the INTERFACE_LINK_LIBRARIES
+  else if (this->PolicyStatusCMP0022 == cmPolicies::WARN
+        || this->PolicyStatusCMP0022 == cmPolicies::OLD)
+    // If CMP0022 is NEW then the plain tll signature sets the
+    // INTERFACE_LINK_LIBRARIES, so if we get here then the project
+    // cleared the property explicitly and we should not fall back
+    // to the link implementation.
     {
     // The link implementation is the default link interface.
     LinkImplementation const* impl = this->GetLinkImplementation(config,
@@ -6635,6 +6543,68 @@ bool cmTarget::ComputeLinkInterface(const char* config, LinkInterface& iface,
       // Targets using this archive need its language runtime libraries.
       iface.Languages = impl->Languages;
       }
+
+    if(this->PolicyStatusCMP0022 == cmPolicies::WARN)
+      {
+      // Compare the link implementation fallback link interface to the
+      // preferred new link interface property and warn if different.
+      cmListFileBacktrace lfbt;
+      cmGeneratorExpression ge(lfbt);
+      cmGeneratorExpressionDAGChecker dagChecker(lfbt, this->GetName(),
+                                      "INTERFACE_LINK_LIBRARIES", 0, 0);
+      std::vector<std::string> ifaceLibs;
+      const char* newExplicitLibraries =
+        this->GetProperty("INTERFACE_LINK_LIBRARIES");
+      cmSystemTools::ExpandListArgument(
+        ge.Parse(newExplicitLibraries)->Evaluate(this->Makefile,
+                                                 config,
+                                                 false,
+                                                 headTarget,
+                                                 this, &dagChecker),
+        ifaceLibs);
+      if (ifaceLibs != impl->Libraries)
+        {
+        std::string oldLibraries;
+        std::string newLibraries;
+        const char *sep = "";
+        for(std::vector<std::string>::const_iterator it
+              = impl->Libraries.begin(); it != impl->Libraries.end(); ++it)
+          {
+          oldLibraries += sep;
+          oldLibraries += *it;
+          sep = ";";
+          }
+        sep = "";
+        for(std::vector<std::string>::const_iterator it
+              = ifaceLibs.begin(); it != ifaceLibs.end(); ++it)
+          {
+          newLibraries += sep;
+          newLibraries += *it;
+          sep = ";";
+          }
+        if(oldLibraries.empty())
+          { oldLibraries = "(empty)"; }
+        if(newLibraries.empty())
+          { newLibraries = "(empty)"; }
+
+        cmOStringStream w;
+        w <<
+          (this->Makefile->GetPolicies()
+           ->GetPolicyWarning(cmPolicies::CMP0022)) << "\n"
+          "Target \"" << this->GetName() << "\" has an "
+          "INTERFACE_LINK_LIBRARIES property.  "
+          "This should be preferred as the source of the link interface "
+          "for this library but because CMP0022 is not set CMake is "
+          "ignoring the property and using the link implementation "
+          "as the link interface instead."
+          "\n"
+          "INTERFACE_LINK_LIBRARIES:\n"
+          "  " << newLibraries << "\n"
+          "Link implementation:\n"
+          "  " << oldLibraries << "\n";
+        this->Makefile->IssueMessage(cmake::AUTHOR_WARNING, w.str());
+        }
+      }
     }
 
   if(this->GetType() == cmTarget::STATIC_LIBRARY)
diff --git a/Source/cmTargetLinkLibrariesCommand.cxx b/Source/cmTargetLinkLibrariesCommand.cxx
index 6030a44..c2f46a1 100644
--- a/Source/cmTargetLinkLibrariesCommand.cxx
+++ b/Source/cmTargetLinkLibrariesCommand.cxx
@@ -379,8 +379,14 @@ cmTargetLinkLibrariesCommand::HandleLibrary(const char* lib,
     {
     this->Makefile
       ->AddLinkLibraryForTarget(this->Target->GetName(), lib, llt);
-    if (this->CurrentProcessingState != ProcessingKeywordPublicInterface
-        && this->CurrentProcessingState != ProcessingPlainPublicInterface)
+    if(this->CurrentProcessingState == ProcessingLinkLibraries)
+      {
+      this->Target->AppendProperty("INTERFACE_LINK_LIBRARIES",
+        this->Target->GetDebugGeneratorExpressions(lib, llt).c_str());
+      return true;
+      }
+    else if(this->CurrentProcessingState != ProcessingKeywordPublicInterface
+            && this->CurrentProcessingState != ProcessingPlainPublicInterface)
       {
       if (this->Target->GetType() == cmTarget::STATIC_LIBRARY)
         {
diff --git a/Source/cmTargetLinkLibrariesCommand.h b/Source/cmTargetLinkLibrariesCommand.h
index f2b2543..2cf6b03 100644
--- a/Source/cmTargetLinkLibrariesCommand.h
+++ b/Source/cmTargetLinkLibrariesCommand.h
@@ -88,14 +88,19 @@ public:
       "See the IMPORTED mode of the add_library command for more "
       "information.  "
       "\n"
-      "Library dependencies are transitive by default.  "
+      "Library dependencies are transitive by default with this signature.  "
       "When this target is linked into another target then the libraries "
       "linked to this target will appear on the link line for the other "
       "target too.  "
-      "See the INTERFACE_LINK_LIBRARIES target property to override the "
-      "set of transitive link dependencies for a target.  "
+      "This transitive \"link interface\" is stored in the "
+      "INTERFACE_LINK_LIBRARIES target property when policy CMP0022 is set "
+      "to NEW and may be overridden by setting the property directly. "
+      "("
+      "When CMP0022 is not set to NEW, transitive linking is builtin "
+      "but may be overridden by the LINK_INTERFACE_LIBRARIES property.  "
       "Calls to other signatures of this command may set the property "
       "making any libraries linked exclusively by this signature private."
+      ")"
       "\n"
       "CMake will also propagate \"usage requirements\" from linked library "
       "targets.  "