Fix rule L011 for implicit aliases (#2683)

* Fix rule L011

* Revert unnecessary change

* Pin markupsafe

src/sqlfluff/rules/L011.py

@@ -56,12 +56,14 @@ def _eval(self, context: RuleContext) -> Optional[LintResult]:
         The use of `raw_stack` is just for working out how much whitespace to add.
 
         """
+        # Config type hints
+        self.aliasing: str
         fixes = []
 
         if context.segment.is_type("alias_expression"):
             if context.parent_stack[-1].is_type(*self._target_elems):
                 if any(e.name.lower() == "as" for e in context.segment.segments):
-                    if self.aliasing == "implicit":  # type: ignore
+                    if self.aliasing == "implicit":
                         if context.segment.segments[0].name.lower() == "as":
 
                             # Remove the AS as we're using implict aliasing
@@ -84,7 +86,7 @@ def _eval(self, context: RuleContext) -> Optional[LintResult]:
 
                             return LintResult(anchor=anchor, fixes=fixes)
 
-                else:
+                elif self.aliasing != "implicit":
                     insert_buff: List[Union[WhitespaceSegment, KeywordSegment]] = []
 
                     # Add initial whitespace if we need to...

test/fixtures/rules/std_rule_cases/L011.yml

@@ -1,5 +1,28 @@
 rule: L011
 
+test_fail_default_explicit:
+  # Add whitespace when fixing implicit aliasing
+  fail_str: select foo.bar from table1 foo
+  fix_str: select foo.bar from table1 AS foo
+
+test_fail_explicit:
+  # Add whitespace when fixing implicit aliasing
+  fail_str: select foo.bar from table1 foo
+  fix_str: select foo.bar from table1 AS foo
+  configs:
+    rules:
+      L011:
+        aliasing: explicit
+
+test_fail_implicit:
+  # Add whitespace when fixing implicit aliasing
+  fail_str: select foo.bar from table1 AS foo
+  fix_str: select foo.bar from table1 foo
+  configs:
+    rules:
+      L011:
+        aliasing: implicit
+
 test_fail_implicit_alias:
   # Add whitespace when fixing implicit aliasing
   fail_str: select foo.bar from (select 1 as bar)foo