Managing very large codebases in Delphi using a Library of Debug and Regular DCUs I built myself

Perhaps I can shed some light on the order of search paths presented to the compiler, which should make clear why the problem happens in the first place and can be cured (at least in your situation) by adding the Debug DCU path at that specific location. All these observations were made with XE7.

There are several places in the IDE where you can specify search paths:

1. Library path (Delphi-Options - Library)
2. Translated Library path (Delphi-Options - Library-Translated)
3. Debug DCU path (Delphi-Options - Library)
4. Translated Debug DCU path (Delphi-Options - Library-Translated)
5. Search path (via Project Options)

When the Library language is set to English, those pathes are given to the compiler in the order 5,1 or 3,5,1 depending of the setting of Use debug .dcus. This is already a bit weird as the debug dcu path takes precedence over the project search path.

So f.i. to make the compiler find our own dcu files of a newer Indy version, we have to place the corresponding paths in front of the paths under 1 and 3.

Now things get complicated when the Library language is set to something different than English. In this case the translated paths come into play resulting in the order 2,5,1 or 4,3,2,5,1 depending of the setting of Use debug .dcus.

To make the above example with a newer Indy version work, you have to tweak the translated paths, too.

The culprit lies in CodeGear.Delphi.Targets, which places the paths in this order. I was able to modify this file so that the natural order of paths is used: 5,2,1 or 5,4,3,2,1. If anyone can confirm that I am allowed to show these changes here I will do. Perhaps I can provide a patch only.

Update: Here are the changes of CodeGear.Delphi.Targets from XE7 as shown by Mercurial

@@ -122,20 +122,19 @@
     <DcpFilename Condition="'$(DcpFilename)'!='' And !HasTrailingSlash('$(DcpFilename)')">$(DcpFilename)\</DcpFilename>
     <DcpFilename Condition="'$(DcpFilename)'!=''">$(DcpFilename)$(MSBuildProjectName).dcp</DcpFilename>

-    <UnitSearchPath Condition="'$(DCC_UnitSearchPath)' != ''">$(DCC_UnitSearchPath);$(DelphiLibraryPath)</UnitSearchPath>
-    <UnitSearchPath Condition="'$(DCC_UnitSearchPath)' == ''">$(DelphiLibraryPath)</UnitSearchPath>
-
+    <UnitSearchPath>$(DelphiLibraryPath)</UnitSearchPath>
     <UnitSearchPath Condition="'$(DCC_TranslatedLibraryPath)' != ''">$(DCC_TranslatedLibraryPath);$(UnitSearchPath)</UnitSearchPath>
     <UnitSearchPath Condition="'$(DCC_DebugDCUs)'=='true' And '$(DelphiDebugDCUPath)'!=''">$(DelphiDebugDCUPath);$(UnitSearchPath)</UnitSearchPath>
     <UnitSearchPath Condition="'$(DCC_DebugDCUs)'=='true' And '$(DCC_TranslatedDebugLibraryPath)' != ''">$(DCC_TranslatedDebugLibraryPath);$(UnitSearchPath)</UnitSearchPath>
-
+    <UnitSearchPath Condition="'$(DCC_UnitSearchPath)' != ''">$(DCC_UnitSearchPath);$(UnitSearchPath)</UnitSearchPath>
+    
     <___ResourcePath Condition="'$(DCC_ResourcePath)' != ''">$(DCC_ResourcePath);$(DelphiLibraryPath)</___ResourcePath>
     <___ResourcePath Condition="'$(DCC_ResourcePath)' == ''">$(DelphiLibraryPath)</___ResourcePath>
+    <___ResourcePath Condition="'$(DCC_TranslatedResourcePath)' != ''">$(DCC_TranslatedResourcePath);$(___ResourcePath)</___ResourcePath>
     <__ResourcePath Condition="'$(DCC_UnitSearchPath)' != ''">$(DCC_UnitSearchPath);$(___ResourcePath)</__ResourcePath>
     <__ResourcePath Condition="'$(DCC_UnitSearchPath)' == ''">$(___ResourcePath)</__ResourcePath>
     <ResourcePath Condition="'$(BRCC_OutputDir)' != ''">$(BRCC_OutputDir);$(__ResourcePath)</ResourcePath>
     <ResourcePath Condition="'$(BRCC_OutputDir)' == ''">$(__ResourcePath)</ResourcePath>
-    <ResourcePath Condition="'$(DCC_TranslatedResourcePath)' != ''">$(DCC_TranslatedResourcePath);$(ResourcePath)</ResourcePath>

     <NameSpace Condition="'DelphiNamespaceSearchPath'!=''">$(NameSpace);$(DelphiNamespaceSearchPath)</NameSpace>