Deprecate taint/trust and related methods, and make the methods no-ops

This removes the related tests, and puts the related specs behind
version guards.  This affects all code in lib, including some
libraries that may want to support older versions of Ruby.

spec/ruby/core/marshal/dump_spec.rb

@@ -581,27 +581,29 @@ describe "Marshal.dump" do
     -> { Marshal.dump(m) }.should raise_error(TypeError)
   end
 
-  it "returns an untainted string if object is untainted" do
-    Marshal.dump(Object.new).tainted?.should be_false
-  end
+  ruby_version_is ''...'2.7' do
+    it "returns an untainted string if object is untainted" do
+      Marshal.dump(Object.new).tainted?.should be_false
+    end
 
-  it "returns a tainted string if object is tainted" do
-    Marshal.dump(Object.new.taint).tainted?.should be_true
-  end
+    it "returns a tainted string if object is tainted" do
+      Marshal.dump(Object.new.taint).tainted?.should be_true
+    end
 
-  it "returns a tainted string if nested object is tainted" do
-    Marshal.dump([[Object.new.taint]]).tainted?.should be_true
-  end
+    it "returns a tainted string if nested object is tainted" do
+      Marshal.dump([[Object.new.taint]]).tainted?.should be_true
+    end
 
-  it "returns a trusted string if object is trusted" do
-    Marshal.dump(Object.new).untrusted?.should be_false
-  end
+    it "returns a trusted string if object is trusted" do
+      Marshal.dump(Object.new).untrusted?.should be_false
+    end
 
-  it "returns an untrusted string if object is untrusted" do
-    Marshal.dump(Object.new.untrust).untrusted?.should be_true
-  end
+    it "returns an untrusted string if object is untrusted" do
+      Marshal.dump(Object.new.untrust).untrusted?.should be_true
+    end
 
-  it "returns an untrusted string if nested object is untrusted" do
-    Marshal.dump([[Object.new.untrust]]).untrusted?.should be_true
+    it "returns an untrusted string if nested object is untrusted" do
+      Marshal.dump([[Object.new.untrust]]).untrusted?.should be_true
+    end
   end
 end

spec/ruby/core/marshal/shared/load.rb

@@ -182,85 +182,87 @@ describe :marshal_load, shared: true do
     end
   end
 
-  it "returns an untainted object if source is untainted" do
-    x = Object.new
-    y = Marshal.send(@method, Marshal.dump(x))
-    y.tainted?.should be_false
-  end
-
-  describe "when source is tainted" do
-    it "returns a tainted object" do
+  ruby_version_is ''...'2.7' do
+    it "returns an untainted object if source is untainted" do
       x = Object.new
-      x.taint
-      s = Marshal.dump(x)
-      y = Marshal.send(@method, s)
-      y.tainted?.should be_true
+      y = Marshal.send(@method, Marshal.dump(x))
+      y.tainted?.should be_false
+    end
 
-      # note that round-trip via Marshal does not preserve
-      # the taintedness at each level of the nested structure
-      y = Marshal.send(@method, Marshal.dump([[x]]))
+    describe "when source is tainted" do
+      it "returns a tainted object" do
+        x = Object.new
+        x.taint
+        s = Marshal.dump(x)
+        y = Marshal.send(@method, s)
+        y.tainted?.should be_true
+
+        # note that round-trip via Marshal does not preserve
+        # the taintedness at each level of the nested structure
+        y = Marshal.send(@method, Marshal.dump([[x]]))
+        y.tainted?.should be_true
+        y.first.tainted?.should be_true
+        y.first.first.tainted?.should be_true
+      end
+
+      it "does not taint Symbols" do
+        x = [:x]
+        y = Marshal.send(@method, Marshal.dump(x).taint)
+        y.tainted?.should be_true
+        y.first.tainted?.should be_false
+      end
+
+      it "does not taint Fixnums" do
+        x = [1]
+        y = Marshal.send(@method, Marshal.dump(x).taint)
+        y.tainted?.should be_true
+        y.first.tainted?.should be_false
+      end
+
+      it "does not taint Bignums" do
+        x = [bignum_value]
+        y = Marshal.send(@method, Marshal.dump(x).taint)
+        y.tainted?.should be_true
+        y.first.tainted?.should be_false
+      end
+
+      it "does not taint Floats" do
+        x = [1.2]
+        y = Marshal.send(@method, Marshal.dump(x).taint)
+        y.tainted?.should be_true
+        y.first.tainted?.should be_false
+      end
+    end
+
+    it "preserves taintedness of nested structure" do
+      x = Object.new
+      a = [[x]]
+      x.taint
+      y = Marshal.send(@method, Marshal.dump(a))
       y.tainted?.should be_true
       y.first.tainted?.should be_true
       y.first.first.tainted?.should be_true
     end
 
-    it "does not taint Symbols" do
-      x = [:x]
-      y = Marshal.send(@method, Marshal.dump(x).taint)
-      y.tainted?.should be_true
-      y.first.tainted?.should be_false
+    it "returns a trusted object if source is trusted" do
+      x = Object.new
+      y = Marshal.send(@method, Marshal.dump(x))
+      y.untrusted?.should be_false
     end
 
-    it "does not taint Fixnums" do
-      x = [1]
-      y = Marshal.send(@method, Marshal.dump(x).taint)
-      y.tainted?.should be_true
-      y.first.tainted?.should be_false
+    it "returns an untrusted object if source is untrusted" do
+      x = Object.new
+      x.untrust
+      y = Marshal.send(@method, Marshal.dump(x))
+      y.untrusted?.should be_true
+
+      # note that round-trip via Marshal does not preserve
+      # the untrustedness at each level of the nested structure
+      y = Marshal.send(@method, Marshal.dump([[x]]))
+      y.untrusted?.should be_true
+      y.first.untrusted?.should be_true
+      y.first.first.untrusted?.should be_true
     end
-
-    it "does not taint Bignums" do
-      x = [bignum_value]
-      y = Marshal.send(@method, Marshal.dump(x).taint)
-      y.tainted?.should be_true
-      y.first.tainted?.should be_false
-    end
-
-    it "does not taint Floats" do
-      x = [1.2]
-      y = Marshal.send(@method, Marshal.dump(x).taint)
-      y.tainted?.should be_true
-      y.first.tainted?.should be_false
-    end
-  end
-
-  it "preserves taintedness of nested structure" do
-    x = Object.new
-    a = [[x]]
-    x.taint
-    y = Marshal.send(@method, Marshal.dump(a))
-    y.tainted?.should be_true
-    y.first.tainted?.should be_true
-    y.first.first.tainted?.should be_true
-  end
-
-  it "returns a trusted object if source is trusted" do
-    x = Object.new
-    y = Marshal.send(@method, Marshal.dump(x))
-    y.untrusted?.should be_false
-  end
-
-  it "returns an untrusted object if source is untrusted" do
-    x = Object.new
-    x.untrust
-    y = Marshal.send(@method, Marshal.dump(x))
-    y.untrusted?.should be_true
-
-    # note that round-trip via Marshal does not preserve
-    # the untrustedness at each level of the nested structure
-    y = Marshal.send(@method, Marshal.dump([[x]]))
-    y.untrusted?.should be_true
-    y.first.untrusted?.should be_true
-    y.first.first.untrusted?.should be_true
   end
 
   # Note: Ruby 1.9 should be compatible with older marshal format