don't re-export internal symbols from other modules

Author: QuietMisdreavus

lib/SymbolGraphGen/SymbolGraph.cpp

@@ -627,6 +627,13 @@ bool SymbolGraph::isImplicitlyPrivate(const Decl *D,
 
     // Special cases below.
 
+    // Symbols from exported-imported modules should only be included if they
+    // were originally public.
+    if (Walker.isFromExportedImportedModule(D) &&
+        VD->getFormalAccess() < AccessLevel::Public) {
+      return true;
+    }
+
     auto BaseName = VD->getBaseName().userFacingName();
 
     // ${MODULE}Version{Number,String} in ${Module}.h

test/SymbolGraph/Module/NoDocExportedImport.swift

@@ -6,6 +6,10 @@
 // RUN: %FileCheck %s --input-file %t/NoDocExportedImport.symbols.json --check-prefix PUBLIC
 // RUN: ls %t | %FileCheck %s --check-prefix FILES
 
+// RUN: %target-swift-frontend %s -module-name NoDocExportedImport -emit-module -emit-module-path /dev/null -I %t -emit-symbol-graph -emit-symbol-graph-dir %t/ -symbol-graph-minimum-access-level internal
+// RUN: %FileCheck %s --input-file %t/NoDocExportedImport.symbols.json --check-prefix INTERNAL
+// RUN: ls %t | %FileCheck %s --check-prefix FILES
+
 @_nodoc @_exported import A
 @_nodoc @_exported import struct B.StructOne
 
@@ -14,6 +18,11 @@
 // PUBLIC-NOT: "precise":"s:1A11SymbolFromAV"
 // PUBLIC-NOT: "precise":"s:1B9StructOneV"
 
+// INTERNAL-NOT: InternalSymbolFromA
+// INTERNAL-NOT: StructTwo
+// INTERNAL-DAG: "precise":"s:1A11SymbolFromAV"
+// INTERNAL-DAG: "precise":"s:1B9StructOneV"
+
 // FIXME: Symbols from `@_exported import` do not get emitted when using swift-symbolgraph-extract
 // This is tracked by https://bugs.swift.org/browse/SR-15921.