Preserve anonymous graph syntax in TriG

4 files changed, 12 insertions, 8 deletions

diff --git a/NEWS b/NEWS
index e3524b41..43beefdd 100644
--- a/NEWS
+++ b/NEWS
@@ -12,6 +12,7 @@ serd (1.0.1) unstable;
   * Bring read/write interface closer to C standard
   * Improve error handling
   * Make nodes opaque
+  * Preserve anonymous graph syntax in TriG
   * Preserve long or short quoting from input documents
   * Remove serd_uri_to_path()
   * Remove support for Turtle named inline nodes extension
@@ -23,7 +24,7 @@ serd (1.0.1) unstable;
   * Use a fixed-size reader stack
   * Use char* for strings in public API
 
- -- David Robillard <d@drobilla.net>  Sat, 31 Jul 2021 23:27:35 +0000
+ -- David Robillard <d@drobilla.net>  Mon, 09 Aug 2021 22:28:20 +0000
 
 serd (0.30.11) unstable;
 
diff --git a/include/serd/serd.h b/include/serd/serd.h
index 3655f0b4..f30026ca 100644
--- a/include/serd/serd.h
+++ b/include/serd/serd.h
@@ -1814,12 +1814,13 @@ typedef enum {
 /// Flags indicating inline abbreviation information for a statement
 typedef enum {
   SERD_EMPTY_S = 1u << 0u, ///< Empty blank node subject
-  SERD_ANON_S  = 1u << 1u, ///< Start of anonymous subject
-  SERD_ANON_O  = 1u << 2u, ///< Start of anonymous object
-  SERD_LIST_S  = 1u << 3u, ///< Start of list subject
-  SERD_LIST_O  = 1u << 4u, ///< Start of list object
-  SERD_TERSE_S = 1u << 5u, ///< Start of terse subject
-  SERD_TERSE_O = 1u << 6u  ///< Start of terse object
+  SERD_EMPTY_G = 1u << 1u, ///< Empty blank node graph
+  SERD_ANON_S  = 1u << 2u, ///< Start of anonymous subject
+  SERD_ANON_O  = 1u << 3u, ///< Start of anonymous object
+  SERD_LIST_S  = 1u << 4u, ///< Start of list subject
+  SERD_LIST_O  = 1u << 5u, ///< Start of list object
+  SERD_TERSE_S = 1u << 6u, ///< Start of terse subject
+  SERD_TERSE_O = 1u << 7u  ///< Start of terse object
 } SerdStatementFlag;
 
 /// Bitwise OR of SerdStatementFlag values
diff --git a/src/n3.c b/src/n3.c
index 7e913d8b..6d4210b4 100644
--- a/src/n3.c
+++ b/src/n3.c
@@ -1198,6 +1198,7 @@ read_block(SerdReader* const reader, ReadContext* const ctx)
     }
 
     ctx->graph = token;
+    (*ctx->flags) |= (s_type == '[' ? SERD_EMPTY_G : 0u);
     return read_wrappedGraph(reader, ctx);
   }
 
diff --git a/src/writer.c b/src/writer.c
index 968d1a9f..5f178a6f 100644
--- a/src/writer.c
+++ b/src/writer.c
@@ -884,7 +884,8 @@ write_blank(SerdWriter* const        writer,
       return write_sep(writer, flags, SEP_LIST_BEGIN);
     }
 
-    if (field == SERD_SUBJECT && (flags & SERD_EMPTY_S)) {
+    if ((field == SERD_SUBJECT && (flags & SERD_EMPTY_S)) ||
+        (field == SERD_GRAPH && (flags & SERD_EMPTY_G))) {
       writer->last_sep = SEP_NONE; // Treat "[]" like a node
       return esink("[]", 2, writer);
     }