Fix yield $-.prop (#305)

* fix yield input pipe'prop

* add test

* update test

* wrap into func

* fix yield constant bug

* wrap into isAllPropsEmpty()

Co-authored-by: Yee <2520865+yixinglu@users.noreply.github.com>

src/validator/GoValidator.cpp

@@ -774,8 +774,7 @@ Status GoValidator::buildColumns() {
     }
 
     auto pool = qctx_->objPool();
-    if (!exprProps_.srcTagProps().empty() || !exprProps_.edgeProps().empty() ||
-        !exprProps_.dstTagProps().empty()) {
+    if (!exprProps_.isAllPropsEmpty() || from_.fromType != FromType::kInstantExpr) {
         srcAndEdgePropCols_ = pool->add(new YieldColumns());
     }
 

src/visitor/DeducePropsVisitor.h

@@ -59,6 +59,12 @@ public:
         return !srcTagProps_.empty() || !dstTagProps_.empty();
     }
 
+    bool isAllPropsEmpty() const {
+        return inputProps_.empty() && varProps_.empty() &&
+               srcTagProps_.empty() && edgeProps_.empty() &&
+               dstTagProps_.empty();
+    }
+
     void insertInputProp(folly::StringPiece prop);
     void insertVarProp(const std::string& outputVar, folly::StringPiece prop);
     void insertSrcTagProp(TagID tagId, folly::StringPiece prop);

tests/query/v1/test_go.py

@@ -202,6 +202,38 @@ class TestGoQuery(NebulaTestSuite):
         self.check_column_names(resp, expected_data["column_names"])
         self.check_out_of_order_result(resp, expected_data["rows"])
 
+    def test_pipe_only_yield_input_prop(self):
+        stmt = '''GO FROM "Tracy McGrady" OVER like YIELD like._dst as vid \
+            | GO FROM $-.vid OVER like YIELD $-.vid as id'''
+        resp = self.execute_query(stmt)
+        self.check_resp_succeeded(resp)
+        expected_data = {
+            "column_names" : ["id"],
+            "rows" : [
+                ["Kobe Bryant"],
+                ["Grant Hill"],
+                ["Rudy Gay"]
+            ]
+        }
+        self.check_column_names(resp, expected_data["column_names"])
+        self.check_out_of_order_result(resp, expected_data["rows"])
+
+    def test_pipe_only_yield_constant(self):
+        stmt = '''GO FROM "Tracy McGrady" OVER like YIELD like._dst as vid \
+            | GO FROM $-.vid OVER like YIELD 3'''
+        resp = self.execute_query(stmt)
+        self.check_resp_succeeded(resp)
+        expected_data = {
+            "column_names" : ["3"],
+            "rows" : [
+                [3],
+                [3],
+                [3]
+            ]
+        }
+        self.check_column_names(resp, expected_data["column_names"])
+        self.check_out_of_order_result(resp, expected_data["rows"])
+
     def test_assignment_empty_result(self):
         stmt = '''$var = GO FROM "-1" OVER like YIELD like._dst as id; \
             GO FROM $var.id OVER like'''