Merge changes Ic890f781,I77b2de10,I3202aba0,I6ddc4296,I18776984, ... into main

* changes:
  doc: fix broken table in operators list
  terminal code eaters: implement OSC
  libexpr: significantly improve error messages for bad attr paths
  tests/functional2: add terminal code eater
  tests/functional2: fix occasional pytest haunting
  attr path parser: fix bug in not rejecting empty attr paths, add unparser

tests/unit/libexpr/attr-path.cc

@@ -0,0 +1,46 @@
+#include "lix/libexpr/attr-path.hh"
+#include "lix/libexpr/attr-set.hh"
+#include "tests/libexpr.hh"
+#include <gtest/gtest.h>
+#include <rapidcheck/gen/Arbitrary.h>
+#include <rapidcheck/gen/Container.h>
+#include <rapidcheck/gen/Predicate.h>
+#include <rapidcheck/gtest.h>
+
+namespace nix {
+
+class AttrPathEval : public LibExprTest
+{
+public:
+    std::pair<Value *, PosIdx> testFindAlongAttrPath(std::string expr, std::string path);
+};
+
+RC_GTEST_PROP(AttrPath, prop_round_trip, ())
+{
+    auto strings = *rc::gen::container<std::vector<std::string>>(
+        rc::gen::container<std::string>(rc::gen::distinctFrom('"'))
+    );
+    auto const unparsed = unparseAttrPath(strings);
+    auto const unparsedReparsed = parseAttrPath(unparsed);
+
+    RC_ASSERT(strings == unparsedReparsed);
+}
+
+std::pair<Value *, PosIdx> AttrPathEval::testFindAlongAttrPath(std::string expr, std::string path)
+{
+    auto v = eval(expr);
+    auto bindings = evalState().ctx.buildBindings(0).finish();
+    return findAlongAttrPath(state, path, *bindings, v);
+}
+
+// n.b. I do not know why we throw for empty attrs but they are apparently
+// disallowed.
+TEST_F(AttrPathEval, emptyAttrsThrows)
+{
+    std::string expr = "{a.\"\".b = 2;}";
+    ASSERT_NO_THROW(testFindAlongAttrPath(expr, "a"));
+    ASSERT_THROW(testFindAlongAttrPath(expr, "a.\"\".b"), Error);
+    ASSERT_THROW(testFindAlongAttrPath(expr, "a.\"\""), Error);
+}
+
+}