Genex: Allow relative paths in INSTALL_INTERFACE.

These paths can be prepended with the ${_IMPORT_PREFIX} generated
in the export file.

Such relative paths were previously an error.

Source/cmExportFileGenerator.cxx

@@ -302,7 +302,8 @@ void cmExportFileGenerator::PopulateIncludeDirectoriesInterface(
   const char* sep = input ? ";" : "";
   includes += sep + tei->InterfaceIncludeDirectories;
   std::string prepro = cmGeneratorExpression::Preprocess(includes,
-                                                          preprocessRule);
+                                                         preprocessRule,
+                                                         true);
   if (!prepro.empty())
     {
     this->ResolveTargetsInGeneratorExpressions(prepro, target,

Source/cmGeneratorExpression.cxx

@@ -228,9 +228,28 @@ static std::string stripAllGeneratorExpressions(const std::string &input)
   return cmGeneratorExpression::StripEmptyListElements(result);
 }
 
+//----------------------------------------------------------------------------
+static void prefixItems(const std::string &content, std::string &result,
+                        const std::string &prefix)
+{
+  std::vector<std::string> entries;
+  cmGeneratorExpression::Split(content, entries);
+  for(std::vector<std::string>::const_iterator ei = entries.begin();
+      ei != entries.end(); ++ei)
+    {
+    if (!cmSystemTools::FileIsFullPath(ei->c_str())
+        && cmGeneratorExpression::Find(*ei) == std::string::npos)
+      {
+      result += prefix;
+      }
+    result += *ei;
+    }
+}
+
 //----------------------------------------------------------------------------
 static std::string stripExportInterface(const std::string &input,
-                          cmGeneratorExpression::PreprocessContext context)
+                          cmGeneratorExpression::PreprocessContext context,
+                          bool resolveRelative)
 {
   std::string result;
 
@@ -289,7 +308,15 @@ static std::string stripExportInterface(const std::string &input,
         else if(context == cmGeneratorExpression::InstallInterface
             && gotInstallInterface)
           {
-          result += input.substr(pos, c - cStart);
+          const std::string content = input.substr(pos, c - cStart);
+          if (resolveRelative)
+            {
+            prefixItems(content, result, "${_IMPORT_PREFIX}/");
+            }
+          else
+            {
+            result += content;
+            }
           }
         break;
         }
@@ -380,7 +407,8 @@ void cmGeneratorExpression::Split(const std::string &input,
 
 //----------------------------------------------------------------------------
 std::string cmGeneratorExpression::Preprocess(const std::string &input,
-                                              PreprocessContext context)
+                                              PreprocessContext context,
+                                              bool resolveRelative)
 {
   if (context == StripAllGeneratorExpressions)
     {
@@ -388,7 +416,7 @@ std::string cmGeneratorExpression::Preprocess(const std::string &input,
     }
   else if (context == BuildInterface || context == InstallInterface)
     {
-    return stripExportInterface(input, context);
+    return stripExportInterface(input, context, resolveRelative);
     }
 
   assert(!"cmGeneratorExpression::Preprocess called with invalid args");

Source/cmGeneratorExpression.h

@@ -57,7 +57,8 @@ public:
   };
 
   static std::string Preprocess(const std::string &input,
-                                PreprocessContext context);
+                                PreprocessContext context,
+                                bool resolveRelative = false);
 
   static void Split(const std::string &input,
                     std::vector<std::string> &output);

Tests/ExportImport/Export/CMakeLists.txt

@@ -140,6 +140,12 @@ install(FILES
 )
 add_include_lib(testLibIncludeRequired6)
 
+file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/testLibIncludeRequired7/testLibIncludeRequired7.h" "// No content\n")
+install(FILES
+  "${CMAKE_CURRENT_BINARY_DIR}/testLibIncludeRequired7/testLibIncludeRequired7.h"
+    DESTINATION include/testLibIncludeRequired7
+)
+
 set_property(TARGET testLibRequired APPEND PROPERTY
   INTERFACE_INCLUDE_DIRECTORIES
     $<TARGET_PROPERTY:testLibIncludeRequired1,INTERFACE_INCLUDE_DIRECTORIES>
@@ -154,6 +160,7 @@ set_property(TARGET testLibRequired APPEND PROPERTY
     $<BUILD_INTERFACE:$<TARGET_PROPERTY:testLibIncludeRequired5,INTERFACE_INCLUDE_DIRECTORIES>>
     # Test that the below is non-fatal
     $<$<STREQUAL:one,two>:$<TARGET_PROPERTY:not_a_target,INTERFACE_INCLUDE_DIRECTORIES>>
+    $<INSTALL_INTERFACE:include/testLibIncludeRequired7>
 )
 
 set_property(TARGET testLibRequired APPEND PROPERTY

Tests/ExportImport/Import/A/deps_iface.c

@@ -2,6 +2,7 @@
 #include "testLibIncludeRequired1.h"
 #include "testLibIncludeRequired2.h"
 #include "testLibIncludeRequired6.h"
+#include "testLibIncludeRequired7.h"
 
 #include "installIncludesTest.h"
 #include "installIncludesTest2.h"