Merge changes I829581a3,I0016970d,I5dac8e77,Ib7560fe5 into main

* changes:
  doc/release-notes: add for pretty printing improvements
  libexpr/print: do not show elided nested items when there are none
  libexpr/print: never show empty attrsets or derivations as «repeated»
  libexpr/print: pretty-print idempotently

src/libexpr/print.cc

@@ -264,22 +264,24 @@ private:
             return true;
         }
 
+        if (options.force) {
+            // The item is going to be forced during printing anyway, but we need its type now.
+            state.forceValue(*item, item->determinePos(noPos));
+        }
+
         // Pretty-print single-item attrsets only if they contain nested
         // structures.
         auto itemType = item->type();
-        return itemType == nList || itemType == nAttrs || itemType == nThunk;
+        return itemType == nList || itemType == nAttrs;
     }
 
     void printAttrs(Value & v, size_t depth)
     {
-        if (seen && !seen->insert(v.attrs).second) {
-            printRepeated();
-            return;
-        }
-
         if (options.force && options.derivationPaths && state.isDerivation(v)) {
             printDerivation(v);
-        } else if (depth < options.maxDepth) {
+        } else if (seen && !v.attrs->empty() && !seen->insert(v.attrs).second) {
+            printRepeated();
+        } else if (depth < options.maxDepth || v.attrs->empty()) {
             increaseIndent();
             output << "{";
 
@@ -335,10 +337,15 @@ private:
             return true;
         }
 
+        if (options.force) {
+            // The item is going to be forced during printing anyway, but we need its type now.
+            state.forceValue(*item, item->determinePos(noPos));
+        }
+
         // Pretty-print single-item lists only if they contain nested
         // structures.
         auto itemType = item->type();
-        return itemType == nList || itemType == nAttrs || itemType == nThunk;
+        return itemType == nList || itemType == nAttrs;
     }
 
     void printList(Value & v, size_t depth)
@@ -348,7 +355,7 @@ private:
             return;
         }
 
-        if (depth < options.maxDepth) {
+        if (depth < options.maxDepth || v.listSize() == 0) {
             increaseIndent();
             output << "[";
             auto listItems = v.listItems();