Fix problem with __import not working (#688)

* Added getPathType to ISlangFileSystemExt.
This is needed so that when searching for a file it's existance can be tested without loading the file. On some platforms a getCanonicalPath can do this - but depending on how getCanonicalPath is implemented, it may not do. This test is made after the relative path is produced before finding the canonical path.

* Test for importing along search path.

* Added comment to explain the issue around WrapFileSystem impl of getPathType.

* Make search path use / not \

3 files changed, 36 insertions, 4 deletions

diff --git a/source/slang/default-file-system.cpp b/source/slang/default-file-system.cpp
index be171d37c..f9c66b7d7 100644
--- a/source/slang/default-file-system.cpp
+++ b/source/slang/default-file-system.cpp
@@ -51,10 +51,16 @@ SlangResult DefaultFileSystem::calcRelativePath(SlangPathType fromPathType, cons
     return SLANG_OK;
 }
 
+SlangResult SLANG_MCALL DefaultFileSystem::getPathType(
+    const char* path,
+    SlangPathType* pathTypeOut)
+{
+    return Path::GetPathType(path, pathTypeOut);   
+}
+
 SlangResult DefaultFileSystem::loadFile(char const* path, ISlangBlob** outBlob)
 {
-    // Default implementation that uses the `core`
-    // libraries facilities for talking to the OS filesystem.
+    // Default implementation that uses the `core` libraries facilities for talking to the OS filesystem.
     //
     // TODO: we might want to conditionally compile these in, so that
     // a user could create a build of Slang that doesn't include any OS
@@ -93,7 +99,7 @@ SlangResult WrapFileSystem::loadFile(char const* path, ISlangBlob** outBlob)
 
 SlangResult WrapFileSystem::getCanoncialPath(const char* path, ISlangBlob** canonicalPathOut)
 {
-    // This isn't a very good 'canonical  path' because the same file might be referenced 
+    // This isn't a very good 'canonical path' because the same file might be referenced 
     // multiple ways - for example by using relative paths. 
     // But it's simple and matches slangs previous behavior. 
     String canonicalPath(path);
@@ -107,4 +113,15 @@ SlangResult WrapFileSystem::calcRelativePath(SlangPathType fromPathType, const c
     return DefaultFileSystem::getSingleton()->calcRelativePath(fromPathType, fromPath, path, pathOut);
 }
 
+SlangResult WrapFileSystem::getPathType(const char* path, SlangPathType* pathTypeOut)
+{
+    // TODO:
+    // This might be undesirable in the longer term because it means that ISlangFileSystem will not be used 
+    // to test file existence - but the file system will be.
+    // 
+    // It would probably be better to use some kind of cache that uses 'loadFile' to load files, but also 
+    // to test for existence.
+    return DefaultFileSystem::getSingleton()->getPathType(path, pathTypeOut); 
+}
+
 } 
\ No newline at end of file
diff --git a/source/slang/default-file-system.h b/source/slang/default-file-system.h
index 62d7cbfc5..47644f5ad 100644
--- a/source/slang/default-file-system.h
+++ b/source/slang/default-file-system.h
@@ -33,11 +33,15 @@ public:
         const char* path,
         ISlangBlob** pathOut) SLANG_OVERRIDE;
 
+    virtual SLANG_NO_THROW SlangResult SLANG_MCALL getPathType(
+        const char* path,
+        SlangPathType* pathTypeOut) SLANG_OVERRIDE;
+
         /// Get a default instance
     static ISlangFileSystemExt* getSingleton() { return &s_singleton; }
 
 private:
-        /// Make so not constructable
+        /// Make so not constructible
     DefaultFileSystem() {}
 
     ISlangUnknown* getInterface(const Guid& guid);
@@ -75,6 +79,10 @@ public:
         const char* path,
         ISlangBlob** pathOut) SLANG_OVERRIDE;
 
+    virtual SLANG_NO_THROW SlangResult SLANG_MCALL getPathType(
+        const char* path,
+        SlangPathType* pathTypeOut) SLANG_OVERRIDE;
+
         /// Ctor
     WrapFileSystem(ISlangFileSystem* fileSystem):
         m_fileSystem(fileSystem)
diff --git a/source/slang/slang.cpp b/source/slang/slang.cpp
index 5461afbf7..996f8e32f 100644
--- a/source/slang/slang.cpp
+++ b/source/slang/slang.cpp
@@ -118,6 +118,13 @@ struct IncludeHandlerImpl : IncludeHandler
             return SLANG_FAIL;
         }
      
+        SlangPathType pathType;
+        SLANG_RETURN_ON_FAIL(fileSystemExt->getPathType(relPath.begin(), &pathType));
+        if (pathType != SLANG_PATH_TYPE_FILE)
+        {
+            return SLANG_E_NOT_FOUND;
+        }
+
         // Get the canonical path
         ComPtr<ISlangBlob> canonicalPathBlob;
         SLANG_RETURN_ON_FAIL(fileSystemExt->getCanoncialPath(relPath.begin(), canonicalPathBlob.writeRef()));