Support .vars for Fiber only when available on platform

lib/im-lost.rb

@@ -245,6 +245,8 @@ def untrace_all!
     #
     # Inspect internal variables of a given object.
     #
+    # @note The dedictaed handling of `Fiber` is platform dependend!
+    #
     # @example Inspect current instance variables
     #   @a = 22
     #   b = 20
@@ -293,7 +295,7 @@ def vars(object)
       @output.puts("= #{location.path}:#{location.lineno}")
       if Thread === object
         _thread_vars(object)
-      elsif Fiber === object
+      elsif @fiber_supported && Fiber === object
         _fiber_vars(object)
       elsif defined?(object.instance_variables)
         _instance_vars(object)
@@ -618,5 +620,7 @@ def initialize(&block)
       @output.puts("  #{tp.path}:#{tp.lineno}") if @exception_locations
     end
 
+  @fiber_supported = !!(defined?(Fiber.current) && defined?(Fiber.storage))
+
   self.trace_calls = true
 end

spec/lib/im-lost_spec.rb

@@ -423,44 +423,48 @@ def bar = :bar
       end
     end
 
-    context 'when the current Fiber is given' do
-      before do
-        Fiber[:var1] = 22
-        Fiber[:var2] = 20
-        Fiber[:var3] = Fiber[:var1] + Fiber[:var2]
-      end
+    if defined?(Fiber.current) && defined?(Fiber.storage)
+      context 'when the current Fiber is given' do
+        before do
+          Fiber[:var1] = 22
+          Fiber[:var2] = 20
+          Fiber[:var3] = Fiber[:var1] + Fiber[:var2]
+        end
 
-      it 'prints the fiber storage' do
-        ImLost.vars(Fiber.current)
+        it 'prints the fiber storage' do
+          ImLost.vars(Fiber.current)
 
-        expect(output).to eq <<~OUTPUT
-          = #{__FILE__}:#{__LINE__ - 3}
-            > fiber storage
-              var1: 22
-              var2: 20
-              var3: 42
-        OUTPUT
-      end
+          expect(output).to eq <<~OUTPUT
+            = #{__FILE__}:#{__LINE__ - 3}
+              > fiber storage
+                var1: 22
+                var2: 20
+                var3: 42
+          OUTPUT
+        end
 
-      it 'returns given fiber' do
-        expect(ImLost.vars(Fiber.current)).to be Fiber.current
+        it 'returns given fiber' do
+          expect(ImLost.vars(Fiber.current)).to be Fiber.current
+        end
       end
-    end
 
-    context 'when a different Fiber is given' do
-      let(:fiber) { Fiber.new { 42 } }
+      context 'when a different Fiber is given' do
+        let(:fiber) { Fiber.new { 42 } }
 
-      after { fiber.kill }
+        after { fiber.kill if defined?(fiber.kill) } # Ruby > v3.3.0
 
-      it 'it prints an error message' do
-        ImLost.vars(fiber)
+        it 'it prints an error message' do
+          ImLost.vars(fiber)
 
-        expect(output).to eq <<~OUTPUT
-          = #{__FILE__}:#{__LINE__ - 3}
-            !!! given Fiber is not the current Fiber
-                #{fiber.inspect}
-        OUTPUT
+          expect(output).to eq <<~OUTPUT
+            = #{__FILE__}:#{__LINE__ - 3}
+              !!! given Fiber is not the current Fiber
+                  #{fiber.inspect}
+          OUTPUT
+        end
       end
+    else
+      pending 'for Fiber is not supported in this platform'
     end
   end