New rule to flag special characters in identifiers

src/sqlfluff/core/default_config.cfg

@@ -96,3 +96,8 @@ require_final_semicolon = False
 
 [sqlfluff:rules:L054]  # GROUP BY/ORDER BY column references.
 group_by_and_order_by_style = consistent
+
+[sqlfluff:rules:L057]  # Special characters in identifiers
+unquoted_identifiers_policy = all
+quoted_identifiers_policy = all
+allow_space_in_identifier = False

src/sqlfluff/core/rules/config_info.py

@@ -124,6 +124,10 @@
             "or implicit positional references"
         ),
     },
+    "allow_space_in_identifier": {
+        "validation": [True, False],
+        "definition": ("Should spaces in identifiers be allowed?"),
+    },
 }
 
 

src/sqlfluff/rules/L057.py

@@ -0,0 +1,92 @@
+"""Implementation of Rule L057."""
+
+from typing import Optional
+
+from sqlfluff.core.rules.base import BaseRule, LintResult, RuleContext
+from sqlfluff.core.rules.doc_decorators import (
+    document_configuration,
+    document_fix_compatible,
+)
+from sqlfluff.rules.L014 import identifiers_policy_applicable
+
+
+@document_configuration
+@document_fix_compatible
+class Rule_L057(BaseRule):
+    """Do not use special characters in object names.
+
+    The functionality for this rule is inherited from :obj:`Rule_L010`.
+
+    | **Anti-pattern**
+    | Using special characters within names when creating or aliasing objects.
+
+    .. code-block:: sql
+
+        CREATE TABLE DBO.ColumnNames
+        (
+            [Internal Space] INT,
+            [Greater>Than] INT,
+            [Less<Than] INT,
+            Number# INT
+        )
+
+    | **Best practice**
+    | Object names should include only alphanumerics and underscores.
+
+    .. code-block:: sql
+
+        CREATE TABLE DBO.ColumnNames
+        (
+            [Internal_Space] INT,
+            [GreaterThan] INT,
+            [LessThan] INT,
+            NumberVal INT
+        )
+
+    """
+
+    config_keywords = [
+        "quoted_identifiers_policy",
+        "unquoted_identifiers_policy",
+        "allow_space_in_identifier",
+    ]
+
+    def _eval(self, context: RuleContext) -> Optional[LintResult]:
+        """Do not use special characters in object names."""
+        if (
+            (
+                context.segment.name == "naked_identifier"
+                and identifiers_policy_applicable(
+                    self.unquoted_identifiers_policy, context.parent_stack  # type: ignore
+                )
+                and not (
+                    context.segment.raw.replace("_", "").isalnum()
+                    or (
+                        self.allow_space_in_identifier  # type: ignore
+                        and context.segment.raw.replace("_", "")
+                        .replace(" ", "")
+                        .isalnum()
+                    )
+                )
+            )
+        ) or (
+            (
+                context.segment.name == "quoted_identifier"
+                and identifiers_policy_applicable(
+                    self.quoted_identifiers_policy, context.parent_stack  # type: ignore
+                )
+                and not (
+                    context.segment.raw[1:-1].replace("_", "").isalnum()
+                    or (
+                        self.allow_space_in_identifier  # type: ignore
+                        and context.segment.raw[1:-1]
+                        .replace("_", "")
+                        .replace(" ", "")
+                        .isalnum()
+                    )
+                )
+            )
+        ):
+            return LintResult(anchor=context.segment)
+        else:
+            return None

test/fixtures/rules/std_rule_cases/L057.yml

@@ -0,0 +1,81 @@
+rule: L057
+
+test_fail_special_chars_create_table_space:
+  fail_str:
+    CREATE TABLE DBO.ColumnNames
+    (
+        "Internal Space" INT
+    )
+
+test_fail_special_chars_create_table_gt:
+  fail_str:
+    CREATE TABLE DBO.ColumnNames
+    (
+        "Greater>Than" INT
+    )
+
+test_fail_special_chars_create_table_lt:
+  fail_str:
+    CREATE TABLE DBO.ColumnNames
+    (
+        "Less<Than" INT
+    )
+
+test_fail_special_chars_create_table_hash_unquoted:
+  fail_str:
+    CREATE TABLE DBO.ColumnNames
+    (
+        Number# INT
+    )
+  configs:
+    core:
+      dialect: tsql
+
+test_pass_special_chars_create_table_none:
+  pass_str:
+    CREATE TABLE DBO.ColumnNames
+    (
+        "No_Internal_Space" INT,
+        GreaterThan INT,
+        LessThan INT,
+        NumberVal INT
+    )
+
+test_pass_special_chars_create_table_none_quoted_tsql:
+  pass_str:
+    CREATE TABLE DBO.ColumnNames
+    (
+        [No_Internal_Space] INT,
+        [GreaterThan] INT,
+        [LessThan] INT,
+        NumberVal INT
+    )
+  configs:
+    core:
+      dialect: tsql
+
+
+test_pass_special_chars_create_table_space_allowed:
+  pass_str:
+    CREATE TABLE DBO.ColumnNames
+    (
+        "Internal Space" INT
+    )
+  configs:
+    rules:
+      L057:
+        allow_space_in_identifier: True
+
+test_fail_special_chars_alias:
+  fail_str:
+    SELECT a as "alias with space"
+    FROM DBO.ColumnNames
+
+test_pass_special_chars_reference:
+  pass_str:
+    SELECT "column with space" as a
+    FROM DBO.ColumnNames
+  configs:
+    rules:
+      L057:
+        quoted_identifiers_policy: aliases