From 3344ce9197926f262fa4eed30f085d72b08af744 Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Tue, 29 Apr 2008 14:17:42 -0400
Subject: ENH: In cmSourceFile::GetLanguage use the file extension (if not
 ambiguous) to determine the language without requiring the source file to
 exist.

---
 Source/cmSourceFile.cxx | 37 +++++++++++++++++++++++++++++++++----
 Source/cmSourceFile.h   |  1 +
 2 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/Source/cmSourceFile.cxx b/Source/cmSourceFile.cxx
index 7b32235..0a848f6 100644
--- a/Source/cmSourceFile.cxx
+++ b/Source/cmSourceFile.cxx
@@ -46,10 +46,28 @@ std::string const& cmSourceFile::GetExtension() const
 //----------------------------------------------------------------------------
 const char* cmSourceFile::GetLanguage()
 {
-  // Compute the final location of the file if necessary.
-  if(this->FullPath.empty())
+  // If the language was set explicitly by the user then use it.
+  if(const char* lang = this->GetProperty("LANGUAGE"))
     {
-    this->GetFullPath();
+    return lang;
+    }
+
+  // Perform computation needed to get the language if necessary.
+  if(this->FullPath.empty() && this->Language.empty())
+    {
+    if(this->Location.ExtensionIsAmbiguous())
+      {
+      // Finalize the file location to get the extension and set the
+      // language.
+      this->GetFullPath();
+      }
+    else
+      {
+      // Use the known extension to get the language if possible.
+      std::string ext =
+        cmSystemTools::GetFilenameLastExtension(this->Location.GetName());
+      this->CheckLanguage(ext);
+      }
     }
 
   // Now try to determine the language.
@@ -252,8 +270,19 @@ void cmSourceFile::CheckExtension()
     }
 
   // Try to identify the source file language from the extension.
+  if(this->Language.empty())
+    {
+    this->CheckLanguage(this->Extension);
+    }
+}
+
+//----------------------------------------------------------------------------
+void cmSourceFile::CheckLanguage(std::string const& ext)
+{
+  // Try to identify the source file language from the extension.
+  cmMakefile* mf = this->Location.GetMakefile();
   cmGlobalGenerator* gg = mf->GetLocalGenerator()->GetGlobalGenerator();
-  if(const char* l = gg->GetLanguageFromExtension(this->Extension.c_str()))
+  if(const char* l = gg->GetLanguageFromExtension(ext.c_str()))
     {
     this->Language = l;
     }
diff --git a/Source/cmSourceFile.h b/Source/cmSourceFile.h
index 1eca56e..59cb7db 100644
--- a/Source/cmSourceFile.h
+++ b/Source/cmSourceFile.h
@@ -116,6 +116,7 @@ private:
   bool FindFullPath();
   bool TryFullPath(const char* tryPath, const char* ext);
   void CheckExtension();
+  void CheckLanguage(std::string const& ext);
 
   std::vector<std::string> Depends;
 };
-- 
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