string-functions: fix a subtle bug on [] calls of Table

NEWS.md

@@ -2,6 +2,8 @@
 
 ## [unreleased]
 
+- Fix a subtle bug on table access as in `table[:col]` in certain situations.
+
 ## Release v2.3.1/v1.5.1 (20-12-2024)
 
 - Fallback to Ruby's Warning module if ActiveSupport doesn't exist. Relevant for old Rails versions.

lib/arel_extensions/string_functions.rb

@@ -47,14 +47,27 @@ def substring start, len = nil
       ArelExtensions::Nodes::Substring.new [self, start, len]
     end
 
-    def [](start, ind = nil)
-      start += 1 if start.is_a?(Integer)
-      if start.is_a?(Range)
+    # Return a [ArelExtensions::Nodes::Substring] if `start` is a [Range] or an
+    # [Integer].
+    #
+    # Return the result to `self.send(start)` if it's a [String|Symbol]. The
+    # assumption is that you're trying to reach an [Arel::Table]'s
+    # [Arel::Attribute].
+    #
+    # @note `ind` should be an [Integer|NilClass] if `start` is an [Integer].
+    #   It's ignored in all other cases.
+    def [](start, end_ = nil)
+      if start.is_a?(String) || start.is_a?(Symbol)
+        self.send(start)
+      elsif start.is_a?(Range)
         ArelExtensions::Nodes::Substring.new [self, start.begin + 1, start.end - start.begin + 1]
-      elsif start.is_a?(Integer) && !ind
-        ArelExtensions::Nodes::Substring.new [self, start, 1]
+      elsif start.is_a?(Integer) && !end_
+        ArelExtensions::Nodes::Substring.new [self, start + 1, 1]
+      elsif start.is_a?(Integer)
+        start += 1
+        ArelExtensions::Nodes::Substring.new [self, start, end_ - start + 1]
       else
-        ArelExtensions::Nodes::Substring.new [self, start, ind - start + 1]
+        raise ArgumentError, 'unrecognized argument types; can accept integers, ranges, or strings.'
       end
     end