duck-type values responding to #to_hash or #to_ary rather than checki…

…ng class

lib/jmespath/nodes.rb

@@ -5,10 +5,6 @@ class Node
       def visit(value)
       end
 
-      def hash_like?(value)
-        Hash === value || Struct === value
-      end
-
       def optimize
         self
       end

lib/jmespath/nodes/field.rb

@@ -8,9 +8,10 @@ def initialize(key)
       end
 
       def visit(value)
-        if value.is_a?(Array) && @key.is_a?(Integer)
-          value[@key]
-        elsif value.is_a?(Hash)
+        if value.respond_to?(:to_ary) && @key.is_a?(Integer)
+          value.to_ary[@key]
+        elsif value.respond_to?(:to_hash)
+          value = value.to_hash
           if !(v = value[@key]).nil?
             v
           elsif @key_sym && !(v = value[@key_sym]).nil?
@@ -48,9 +49,10 @@ def initialize(keys)
 
       def visit(obj)
         @keys.reduce(obj) do |value, key|
-          if value.is_a?(Array) && key.is_a?(Integer)
-            value[key]
-          elsif value.is_a?(Hash)
+          if value.respond_to?(:to_ary) && key.is_a?(Integer)
+            value.to_ary[key]
+          elsif value.respond_to?(:to_hash)
+            value = value.to_hash
             if !(v = value[key]).nil?
               v
             elsif (sym = @key_syms[key]) && !(v = value[sym]).nil?

lib/jmespath/nodes/flatten.rb

@@ -8,10 +8,10 @@ def initialize(child)
 
       def visit(value)
         value = @child.visit(value)
-        if Array === value
-          value.each_with_object([]) do |v, values|
-            if Array === v
-              values.concat(v)
+        if value.respond_to?(:to_ary)
+          value.to_ary.each_with_object([]) do |v, values|
+            if v.respond_to?(:to_ary)
+              values.concat(v.to_ary)
             else
               values.push(v)
             end

lib/jmespath/nodes/function.rb

@@ -50,14 +50,20 @@ def call(args)
 
     module TypeChecker
       def get_type(value)
-        case value
-        when String then STRING_TYPE
-        when true, false then BOOLEAN_TYPE
-        when nil then NULL_TYPE
-        when Numeric then NUMBER_TYPE
-        when Hash, Struct then OBJECT_TYPE
-        when Array then ARRAY_TYPE
-        when Expression then EXPRESSION_TYPE
+        if value.respond_to?(:to_str)
+          STRING_TYPE
+        elsif value == true || value == false
+          BOOLEAN_TYPE
+        elsif value == nil
+          NULL_TYPE
+        elsif value.is_a?(Numeric)
+          NUMBER_TYPE
+        elsif value.respond_to?(:to_hash) || value.is_a?(Struct)
+          OBJECT_TYPE
+        elsif value.respond_to?(:to_ary)
+          ARRAY_TYPE
+        elsif value.is_a?(Expression)
+          EXPRESSION_TYPE
         end
       end
 
@@ -106,7 +112,8 @@ def call(args)
         else
           return maybe_raise Errors::InvalidArityError, "function avg() expects one argument"
         end
-        if Array === values
+        if values.respond_to?(:to_ary)
+          values = values.to_ary
           return nil if values.empty?
           values.inject(0) do |total,n|
             if Numeric === n
@@ -145,8 +152,10 @@ def call(args)
         if args.count == 2
           haystack = args[0]
           needle = args[1]
-          if String === haystack || Array === haystack
-            haystack.include?(needle)
+          if haystack.respond_to?(:to_str)
+            haystack.to_str.include?(needle)
+          elsif haystack.respond_to?(:to_ary)
+            haystack.to_ary.include?(needle)
           else
             return maybe_raise Errors::InvalidTypeError, "contains expects 2nd arg to be a list"
           end
@@ -182,9 +191,10 @@ def call(args)
         else
           return maybe_raise Errors::InvalidArityError, "function length() expects one argument"
         end
-        case value
-        when Hash, Array, String then value.size
-        else return maybe_raise Errors::InvalidTypeError, "function length() expects string, array or object"
+        if value.respond_to?(:to_hash) || value.respond_to?(:to_ary) || value.respond_to?(:to_str)
+          value.size
+        else
+          return maybe_raise Errors::InvalidTypeError, "function length() expects string, array or object"
         end
       end
     end
@@ -202,8 +212,8 @@ def call(args)
         else
           return maybe_raise Errors::InvalidTypeError, "function map() expects the first argument to be an expression"
         end
-        if Array === args[1]
-          list = args[1]
+        if args[1].respond_to?(:to_ary)
+          list = args[1].to_ary
         else
           return maybe_raise Errors::InvalidTypeError, "function map() expects the second argument to be an list"
         end
@@ -223,7 +233,8 @@ def call(args)
         else
           return maybe_raise Errors::InvalidArityError, "function max() expects one argument"
         end
-        if Array === values
+        if values.respond_to?(:to_ary)
+          values = values.to_ary
           return nil if values.empty?
           first = values.first
           first_type = get_type(first)
@@ -258,7 +269,8 @@ def call(args)
         else
           return maybe_raise Errors::InvalidArityError, "function min() expects one argument"
         end
-        if Array === values
+        if values.respond_to?(:to_ary)
+          values = values.to_ary
           return nil if values.empty?
           first = values.first
           first_type = get_type(first)
@@ -302,12 +314,10 @@ class KeysFunction < Function
       def call(args)
         if args.count == 1
           value = args.first
-          if hash_like?(value)
-            case value
-            when Hash then value.keys.map(&:to_s)
-            when Struct then value.members.map(&:to_s)
-            else raise NotImplementedError
-            end
+          if value.respond_to?(:to_hash)
+            value.to_hash.keys.map(&:to_s)
+          elsif value.is_a?(Struct)
+            value.members.map(&:to_s)
           else
             return maybe_raise Errors::InvalidTypeError, "function keys() expects a hash"
           end
@@ -323,10 +333,12 @@ class ValuesFunction < Function
       def call(args)
         if args.count == 1
           value = args.first
-          if hash_like?(value)
-            value.values
-          elsif Array === value
-            value
+          if value.respond_to?(:to_hash)
+            value.to_hash.values
+          elsif value.is_a?(Struct)
+            value.to_h.values
+          elsif value.respond_to?(:to_ary)
+            value.to_ary
           else
             return maybe_raise Errors::InvalidTypeError, "function values() expects an array or a hash"
           end
@@ -345,8 +357,8 @@ def call(args)
           values = args[1]
           if !(String === glue)
             return maybe_raise Errors::InvalidTypeError, "function join() expects the first argument to be a string"
-          elsif Array === values && values.all? { |v| String === v }
-            values.join(glue)
+          elsif values.respond_to?(:to_ary) && values.to_ary.all? { |v| String === v }
+            values.to_ary.join(glue)
           else
             return maybe_raise Errors::InvalidTypeError, "function join() expects values to be an array of strings"
           end
@@ -390,8 +402,8 @@ class SumFunction < Function
       FUNCTIONS['sum'] = self
 
       def call(args)
-        if args.count == 1 && Array === args.first
-          args.first.inject(0) do |sum,n|
+        if args.count == 1 && args.first.respond_to?(:to_ary)
+          args.first.to_ary.inject(0) do |sum,n|
             if Numeric === n
               sum + n
             else
@@ -424,7 +436,8 @@ class SortFunction < Function
       def call(args)
         if args.count == 1
           value = args.first
-          if Array === value
+          if value.respond_to?(:to_ary)
+            value = value.to_ary
             # every element in the list must be of the same type
             array_type = get_type(value[0])
             if array_type == STRING_TYPE || array_type == NUMBER_TYPE || value.size == 0
@@ -616,7 +629,9 @@ def call(args)
           return maybe_raise Errors::InvalidArityError, msg
         end
         value = args.first
-        if Array === value || String === value
+        if value.respond_to?(:to_ary)
+          value.to_ary.reverse
+        elsif String === value
           value.reverse
         else
           msg = "function reverse() expects an array or string"
@@ -630,7 +645,7 @@ class ToArrayFunction < Function
 
       def call(args)
         value = args.first
-        Array === value ? value : [value]
+        value.respond_to?(:to_ary) ? value.to_ary : [value]
       end
     end
   end

lib/jmespath/nodes/projection.rb

@@ -45,8 +45,8 @@ def visit(value)
 
     class ArrayProjection < Projection
       def extract_targets(target)
-        if Array === target
-          target
+        if target.respond_to?(:to_ary)
+          target.to_ary
         else
           nil
         end
@@ -63,8 +63,10 @@ class FastArrayProjection < ArrayProjection
 
     class ObjectProjection < Projection
       def extract_targets(target)
-        if hash_like?(target)
-          target.values
+        if target.respond_to?(:to_hash)
+          target.to_hash.values
+        elsif target.is_a?(Struct)
+          target.to_h.values
         else
           nil
         end

lib/jmespath/nodes/slice.rb

@@ -10,7 +10,7 @@ def initialize(start, stop, step)
       end
 
       def visit(value)
-        if String === value || Array === value
+        if (value = value.respond_to?(:to_str) ? value.to_str : value.respond_to?(:to_ary) ? value.to_ary : nil)
           start, stop, step = adjust_slice(value.size, @start, @stop, @step)
           result = []
           if step > 0