Improvements in -X support (#1852)

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

* Added SourceLoc handling for command line parsing.

* Fix typo in debug.

* Fix issue around the DiagnosticSink used in options parsing not having a writer available - by having DiagnosticSink parenting.

* Small rename for clarity.

* WIP extracting command line args for downstream tools.

* Unit tests/bug fixes around extracting args.

* Use DownstreamArgs in the EndToEndCompileRequest

* Passing downstream compiler options downstream.

* Fix issue with endToEndReq being nullptr.

* Fix issue with diagnostics number change.

* Small improvements to how the source line is displayed if it's too long.
Default to 120, as suggested in previous review.

* Make render test use x-args parsing and CommandArgReader.

* Added missing diagnostics.

* More DownstreamArgs to linkage so can be seen by 'components'.
Added dxc-x-arg test.

* Used combination of name and args instead of two Lists, which whilst equivalent was perhaps a little confusing.

* Added documentation for -X support.

* Added test for x-args parsing diagnostic. Improved diagnostic with list of known names.

* Fix issues from merge.

* Fix lookup for -matrix-layout-column-major in render test.

* Remove commented out line.

4 files changed, 31 insertions, 28 deletions

diff --git a/source/slang/slang-compiler.cpp b/source/slang/slang-compiler.cpp
index 31ead4cc3..9a2a69248 100755
--- a/source/slang/slang-compiler.cpp
+++ b/source/slang/slang-compiler.cpp
@@ -967,13 +967,14 @@ namespace Slang
         /* Let's set the compiler specific options 
 
           We can only do this if the endToEndReq is set. */
-        if (endToEndReq)
         {
+            auto linkage = targetReq->getLinkage();
+        
             auto name = TypeTextUtil::getPassThroughName((SlangPassThrough)downstreamCompiler);
-            const Index nameIndex = endToEndReq->m_downstreamArgs.findName(name);
+            const Index nameIndex = linkage->m_downstreamArgs.findName(name);
             if (nameIndex >= 0)
             {
-                auto& args = endToEndReq->m_downstreamArgs.getArgsAt(nameIndex);
+                auto& args = linkage->m_downstreamArgs.getArgsAt(nameIndex);
                 for (const auto& arg : args.m_args)
                 {
                     options.compilerSpecificArguments.add(arg.value);
diff --git a/source/slang/slang-compiler.h b/source/slang/slang-compiler.h
index 603ee0bb5..e3d8e506c 100755
--- a/source/slang/slang-compiler.h
+++ b/source/slang/slang-compiler.h
@@ -1349,6 +1349,9 @@ namespace Slang
         // Determine whether to output heterogeneity-related code
         bool m_heterogeneous = false;
 
+        /// Holds any args that are destined for downstream compilers/tools etc
+        DownstreamArgs m_downstreamArgs;
+
         // Name pool for looking up names
         NamePool namePool;
 
@@ -2036,9 +2039,6 @@ namespace Slang
         };
         Dictionary<TargetRequest*, RefPtr<TargetInfo>> m_targetInfos;
 
-            /// Holds any args that are destined for downstream compilers/tools etc
-        DownstreamArgs m_downstreamArgs;
-
             /// Writes the modules in a container to the stream
         SlangResult writeContainerToStream(Stream* stream);
         
diff --git a/source/slang/slang-options.cpp b/source/slang/slang-options.cpp
index f4cd2e4ef..00372ca3c 100644
--- a/source/slang/slang-options.cpp
+++ b/source/slang/slang-options.cpp
@@ -410,7 +410,7 @@ struct OptionsParser
 
         DiagnosticSink* requestSink = requestImpl->getSink();
 
-        CommandLineContext* cmdLineContext = requestImpl->m_downstreamArgs.getContext();
+        CommandLineContext* cmdLineContext = requestImpl->getLinkage()->m_downstreamArgs.getContext();
         
         // Why create a new DiagnosticSink?
         // We *don't* want the lexer that comes as default (it's for Slang source!)
@@ -437,9 +437,6 @@ struct OptionsParser
             parseSink.setFlag(DiagnosticSink::Flag::SourceLocationLine);
         }
 
-        // We don't know how big the terminal is.. let's guess 120 for now 
-        parseSink.setSourceLineMaxLength(120);
-
         // All diagnostics will also be sent to requestSink
         parseSink.setParentSink(requestSink);
 
@@ -451,8 +448,11 @@ struct OptionsParser
         // Doing so will allocate some SourceLoc space from the CommandLineContext.
         args.setArgs(argv, argc);
 
-        // Before we do anything else lets strip out all of the downstream arguments.
-        SLANG_RETURN_ON_FAIL(requestImpl->m_downstreamArgs.stripDownstreamArgs(args, 0, sink));
+        {
+            auto linkage = requestImpl->getLinkage();
+            // Before we do anything else lets strip out all of the downstream arguments.
+            SLANG_RETURN_ON_FAIL(linkage->m_downstreamArgs.stripDownstreamArgs(args, 0, sink));
+        }
 
         CommandLineReader reader(&args, sink);
 
diff --git a/source/slang/slang.cpp b/source/slang/slang.cpp
index 9a109f9d7..613992354 100644
--- a/source/slang/slang.cpp
+++ b/source/slang/slang.cpp
@@ -731,6 +731,24 @@ Linkage::Linkage(Session* session, ASTBuilder* astBuilder, Linkage* builtinLinka
             mapNameToLoadedModules.Add(pair.Key, pair.Value);
         }
     }
+
+    {
+        RefPtr<CommandLineContext> context = new CommandLineContext;
+        m_downstreamArgs = DownstreamArgs(context);
+
+        // Add all of the possible names we allow for downstream tools
+        {
+            for (Index i = SLANG_PASS_THROUGH_NONE + 1; i < SLANG_PASS_THROUGH_COUNT_OF; ++i)
+            {
+                m_downstreamArgs.addName(TypeTextUtil::getPassThroughName(SlangPassThrough(i)));
+            }
+
+            // Generic downstream tool
+            m_downstreamArgs.addName("downstream");
+            // Generic downstream linker
+            m_downstreamArgs.addName("linker");
+        }
+    }
 }
 
 ISlangUnknown* Linkage::getInterface(const Guid& guid)
@@ -2047,22 +2065,6 @@ void EndToEndCompileRequest::init()
     m_frontEndReq = new FrontEndCompileRequest(getLinkage(), m_writers, getSink());
 
     m_backEndReq = new BackEndCompileRequest(getLinkage(), getSink());
-
-    RefPtr<CommandLineContext> context = new CommandLineContext;
-    m_downstreamArgs = DownstreamArgs(context);
-
-    // Add all of the possible names we allow for downstream tools
-    {
-        for (Index i = SLANG_PASS_THROUGH_NONE + 1; i < SLANG_PASS_THROUGH_COUNT_OF; ++i)
-        {
-            m_downstreamArgs.addName(TypeTextUtil::getPassThroughName(SlangPassThrough(i)));
-        }
-
-        // Generic downstream tool
-        m_downstreamArgs.addName("downstream");
-        // Generic downstream linker
-        m_downstreamArgs.addName("linker");
-    }
 }
 
 SlangResult EndToEndCompileRequest::executeActionsInner()