YQL-19747: Fix caret token position

Outcomes:
1. Need to think more deeply about library interfaces. If you think that an interface is redundant, think again, because author knows a usecase that you do not imagine.
2. If you are lazy now to implement something robustly, think twice because the day will come and this code
will fire.

The problem was that on input ``` ... cluster.`/yql/t#` ``` C3 receives only a prefix ``` ... cluster.`/yql/t ``` and a token stream produced was incorrect and therefore completions too.

---

- Related to `YQL-19747`
- Related to https://github.com/ytsaurus/ytsaurus/pull/1257
- Related to https://github.com/ydb-platform/ydb/issues/9056

---

Pull Request resolved: https://github.com/ytsaurus/ytsaurus/pull/1271
commit_hash:8bf5f2683c9e41963003da923f255f63b898aac5

1 files changed, 18 insertions, 1 deletions

diff --git a/yql/essentials/sql/v1/complete/syntax/local.cpp b/yql/essentials/sql/v1/complete/syntax/local.cpp
index 549208d4cab..c20b67d2042 100644
--- a/yql/essentials/sql/v1/complete/syntax/local.cpp
+++ b/yql/essentials/sql/v1/complete/syntax/local.cpp
@@ -68,7 +68,7 @@ namespace NSQLComplete {
                 return {};
             }
 
-            TC3Candidates candidates = C3_.Complete(statement);
+            TC3Candidates candidates = C3Complete(statement, context);
 
             TLocalSyntaxContext result;
 
@@ -118,6 +118,23 @@ namespace NSQLComplete {
             return GetC3PreferredRules();
         }
 
+        TC3Candidates C3Complete(TCompletionInput statement, const TCursorTokenContext& context) {
+            auto enclosing = context.Enclosing();
+
+            size_t caretTokenIndex = context.Cursor.NextTokenIndex;
+            if (enclosing.Defined()) {
+                caretTokenIndex = enclosing->Index;
+            }
+
+            TStringBuf text = statement.Text;
+            if (enclosing.Defined() && enclosing->Base->Name == "NOT_EQUALS2") {
+                text = statement.Text.Head(statement.CursorPosition);
+                caretTokenIndex += 1;
+            }
+
+            return C3_.Complete(text, caretTokenIndex);
+        }
+
         TLocalSyntaxContext::TKeywords SiftedKeywords(const TC3Candidates& candidates) const {
             const auto& vocabulary = Grammar_->GetVocabulary();
             const auto& keywordTokens = Grammar_->GetKeywordTokens();