Allow #include of absolute paths (#1555)

* #include an absolute path didn't work - because paths were taken to always be relative.

* Improve comments.

* Small comment improvement.

1 files changed, 25 insertions, 6 deletions

diff --git a/source/slang/slang-include-system.cpp b/source/slang/slang-include-system.cpp
index 66aeb3f67..891d376f6 100644
--- a/source/slang/slang-include-system.cpp
+++ b/source/slang/slang-include-system.cpp
@@ -9,15 +9,26 @@ namespace Slang
 
 SlangResult IncludeSystem::findFile(SlangPathType fromPathType, const String& fromPath, const String& path, PathInfo& outPathInfo)
 {
-    // Get relative path
-    ComPtr<ISlangBlob> combinedPathBlob;
-    SLANG_RETURN_ON_FAIL(m_fileSystemExt->calcCombinedPath(fromPathType, fromPath.begin(), path.begin(), combinedPathBlob.writeRef()));
-    String combinedPath(StringUtil::getString(combinedPathBlob));
-    if (combinedPath.getLength() <= 0)
+    String combinedPath;
+
+    if (fromPath.getLength() == 0 || Path::isAbsolute(path))
     {
-        return SLANG_FAIL;
+        // If the path is absolute or the fromPath is empty, the combined path is just the path
+        combinedPath = path;
+    }
+    else
+    {
+        // Get relative path
+        ComPtr<ISlangBlob> combinedPathBlob;
+        SLANG_RETURN_ON_FAIL(m_fileSystemExt->calcCombinedPath(fromPathType, fromPath.begin(), path.begin(), combinedPathBlob.writeRef()));
+        combinedPath = StringUtil::getString(combinedPathBlob);
+        if (combinedPath.getLength() <= 0)
+        {
+            return SLANG_FAIL;
+        }
     }
 
+    // This checks the path exists
     SlangPathType pathType;
     SLANG_RETURN_ON_FAIL(m_fileSystemExt->getPathType(combinedPath.begin(), &pathType));
     if (pathType != SLANG_PATH_TYPE_FILE)
@@ -55,6 +66,14 @@ SlangResult IncludeSystem::findFile(String const& pathToInclude, String const& p
 {
     outPathInfo.type = PathInfo::Type::Unknown;
 
+    // If it's absolute we only have to try and find if it's there - no need to look at search paths
+    if (Path::isAbsolute(pathToInclude))
+    {
+        // We pass in "" as the from path, so ensure no from path is taken into account
+        // and to allow easy identification that this is in effect absolute
+        return findFile(SLANG_PATH_TYPE_DIRECTORY, UnownedStringSlice::fromLiteral(""), pathToInclude, outPathInfo);
+    }
+
     // Try just relative to current path
     {
         SlangResult res = findFile(SLANG_PATH_TYPE_FILE, pathIncludedFrom, pathToInclude, outPathInfo);