extend the parser's list of binary operators

This is still not perfect, and there is more to do, since as the
commentary notes
 * unary operators are excluded for now
 * assignment is used differently, but is included
 * arrow operators should expect a literal on the RHS
 * BETWEEN and CASE WHEN are more complex to handle in the same way
 * IS and some other binary operators currently cause an infinite loop,
   which we catch, but then get generic completions

But, this still improves our recognition of operators in context.

Operators taken from
 * https://dev.mysql.com/doc/refman/9.6/en/built-in-function-reference.html

One xfailed test is included for the arrow-operator case.

Author: rolandwalker

changelog.md

@@ -1,3 +1,11 @@
+Upcoming (TBD)
+==============
+
+Features
+---------
+* Improve completions after operators, by recognizing more operators.
+
+
 1.64.0 (2026/03/13)
 ==============
 

mycli/packages/completion_engine.py

@@ -17,6 +17,30 @@
     re.IGNORECASE,
 )
 
+# missing because not binary
+#   BETWEEN
+#   CASE
+# missing because parens are used
+#   IN(), and others
+# unary operands might need to have another set
+#   not, !, ~
+# arrow operators only take a literal on the right
+#   and so might need different treatment
+# := might also need a different context
+# sqlparse would call these identifiers, so they are excluded
+#   xor
+# these are hitting the recursion guard, and so not completing after
+# so we might as well leave them out:
+#   is, 'is not', mod
+# sqlparse might also parse "not null" together
+# should also verify how sqlparse parses every space-containing case
+BINARY_OPERANDS = {
+    '&', '>', '>>', '>=', '<', '<>', '!=', '<<', '<=', '<=>', '%',
+    '*', '+', '-', '->', '->>', '/', ':=', '=', '^', 'and', '&&', 'div',
+    'like', 'not like', 'not regexp', 'or', '||', 'regexp', 'rlike',
+    'sounds like', '|',
+}  # fmt: skip
+
 
 def _enum_value_suggestion(text_before_cursor: str, full_text: str) -> dict[str, Any] | None:
     match = _ENUM_VALUE_RE.search(text_before_cursor)
@@ -299,8 +323,6 @@ def suggest_based_on_last_token(
     else:
         token_v = token.value.lower()
 
-    is_operand = lambda x: x and any(x.endswith(op) for op in ["+", "-", "*", "/"])  # noqa: E731
-
     if not token:
         return [{"type": "keyword"}, {"type": "special"}]
     elif token_v == "*":
@@ -468,11 +490,19 @@ def suggest_based_on_last_token(
     elif is_inside_quotes(text_before_cursor, -1) in ['single', 'double']:
         return []
 
-    elif token_v.endswith(",") or is_operand(token_v) or token_v in ["=", "and", "or"]:
+    elif token_v.endswith(",") or token_v in BINARY_OPERANDS:
         original_text = text_before_cursor
         prev_keyword, text_before_cursor = find_prev_keyword(text_before_cursor)
         enum_suggestion = _enum_value_suggestion(original_text, full_text)
-        fallback = suggest_based_on_last_token(prev_keyword, text_before_cursor, None, full_text, identifier) if prev_keyword else []
+
+        # guard against non-progressing parser rewinds, which can otherwise
+        # recurse forever on some operator shapes.
+        if prev_keyword and text_before_cursor.rstrip() != original_text.rstrip():
+            fallback = suggest_based_on_last_token(prev_keyword, text_before_cursor, None, full_text, identifier)
+        else:
+            # perhaps this fallback should include columns
+            fallback = [{"type": "keyword"}]
+
         if enum_suggestion and _is_where_or_having(prev_keyword):
             return [enum_suggestion] + fallback
         return fallback

test/test_completion_engine.py

@@ -1,6 +1,9 @@
 # type: ignore
 
+from unittest.mock import patch
+
 import pytest
+import sqlparse
 
 from mycli.packages import special
 from mycli.packages.completion_engine import (
@@ -114,6 +117,27 @@ def test_operand_inside_function_suggests_cols2():
     assert suggestion == [{"type": "column", "tables": [(None, "tbl", None)]}]
 
 
+def test_operand_inside_function_suggests_cols3():
+    suggestion = suggest_type("SELECT MAX(col1 ||  FROM tbl", "SELECT MAX(col1 || ")
+    assert suggestion == [{"type": "column", "tables": [(None, "tbl", None)]}]
+
+
+def test_operand_inside_function_suggests_cols4():
+    suggestion = suggest_type("SELECT MAX(col1 LIKE  FROM tbl", "SELECT MAX(col1 LIKE ")
+    assert suggestion == [{"type": "column", "tables": [(None, "tbl", None)]}]
+
+
+def test_operand_inside_function_suggests_cols5():
+    suggestion = suggest_type("SELECT MAX(col1 DIV  FROM tbl", "SELECT MAX(col1 DIV ")
+    assert suggestion == [{"type": "column", "tables": [(None, "tbl", None)]}]
+
+
+@pytest.mark.xfail
+def test_arrow_op_inside_function_suggests_nothing():
+    suggestion = suggest_type("SELECT MAX(col1->  FROM tbl", "SELECT MAX(col1->")
+    assert suggestion == []
+
+
 def test_select_suggests_cols_and_funcs():
     suggestions = suggest_type("SELECT ", "SELECT ")
     assert sorted_dicts(suggestions) == sorted_dicts([
@@ -406,6 +430,8 @@ def test_join_alias_dot_suggests_cols2(sql):
     [
         "select a.x, b.y from abc a join bcd b on ",
         "select a.x, b.y from abc a join bcd b on a.id = b.id OR ",
+        "select a.x, b.y from abc a join bcd b on a.id = b.id + ",
+        "select a.x, b.y from abc a join bcd b on a.id = b.id < ",
     ],
 )
 def test_on_suggests_aliases(sql):