Mention qualified property name in Get or Set errors (TODO PR num)

Before:
The caller gets a D-Bus Error which includes interface and method name
and they are org.freedesktop.DBus.Properties.Get which is not enough.

After:
Also include the property name and its interface.

Author: mvidner

lib/dbus/object.rb

@@ -455,11 +455,16 @@ def interfaces_and_properties
         property = dbus_lookup_property(interface_name, property_name)
 
         if property.readable?
-          ruby_name = property.ruby_name
-          value = public_send(ruby_name)
-          # may raise, DBus.error or https://ruby-doc.com/core-3.1.0/TypeError.html
-          typed_value = Data.make_typed(property.type, value)
-          [typed_value]
+          begin
+            ruby_name = property.ruby_name
+            value = public_send(ruby_name)
+            # may raise, DBus.error or https://ruby-doc.com/core-3.1.0/TypeError.html
+            typed_value = Data.make_typed(property.type, value)
+            [typed_value]
+          rescue StandardError => e
+            msg = "When getting '#{interface_name}.#{property_name}': " + e.message
+            raise e.exception(msg)
+          end
         else
           raise DBus.error("org.freedesktop.DBus.Error.PropertyWriteOnly"),
                 "Property '#{interface_name}.#{property_name}' (on object '#{@path}') is not readable"
@@ -470,11 +475,16 @@ def interfaces_and_properties
         property = dbus_lookup_property(interface_name, property_name)
 
         if property.writable?
-          ruby_name_eq = "#{property.ruby_name}="
-          # TODO: declare dbus_method :Set to take :exact argument
-          # and type check it here before passing its :plain value
-          # to the implementation
-          public_send(ruby_name_eq, value)
+          begin
+            ruby_name_eq = "#{property.ruby_name}="
+            # TODO: declare dbus_method :Set to take :exact argument
+            # and type check it here before passing its :plain value
+            # to the implementation
+            public_send(ruby_name_eq, value)
+          rescue StandardError => e
+            msg = "When setting '#{interface_name}.#{property_name}': " + e.message
+            raise e.exception(msg)
+          end
         else
           raise DBus.error("org.freedesktop.DBus.Error.PropertyReadOnly"),
                 "Property '#{interface_name}.#{property_name}' (on object '#{@path}') is not writable"

spec/mock-service/spaghetti-monster.rb

@@ -122,6 +122,8 @@ def initialize(path)
     dbus_attr_reader :read_me, "s"
 
     def write_me=(value)
+      raise "We don't talk about Bruno" if value =~ /Bruno/
+
       @read_me = value
     end
     dbus_writer :write_me, "s"

spec/property_spec.rb

@@ -31,17 +31,36 @@
     expect(iface["ReadMe"]).to eq("READ ME")
   end
 
-  it "gets an error when reading a property whose implementation raises" do
-    expect { @iface["Explosive"] }.to raise_error(DBus::Error, /Something failed/)
+  context "when reading a property fails" do
+    it "gets an error, mentioning the qualified property name" do
+      expect { @iface["Explosive"] } \
+        .to raise_error(DBus::Error, /getting.*SampleInterface.Explosive.*Something failed/)
+    end
   end
 
   it "tests property nonreading" do
     expect { @iface["WriteMe"] }.to raise_error(DBus::Error, /not readable/)
   end
 
-  it "tests property writing" do
-    @iface["ReadOrWriteMe"] = "VALUE"
-    expect(@iface["ReadOrWriteMe"]).to eq("VALUE")
+  context "writing properties" do
+    it "tests property writing" do
+      @iface["ReadOrWriteMe"] = "VALUE"
+      expect(@iface["ReadOrWriteMe"]).to eq("VALUE")
+    end
+
+    context "when writing a read-only property" do
+      it "gets an error, mentioning the qualified property name" do
+        expect { @iface["ReadMe"] = "WROTE" }  \
+          .to raise_error(DBus::Error, /SampleInterface.ReadMe.*not writable/)
+      end
+    end
+
+    context "when writing a property fails" do
+      it "gets an error, mentioning the qualified property name" do
+        expect { @iface["WriteMe"] = "Bruno is a city in Czechia" } \
+          .to raise_error(DBus::Error, /setting.*SampleInterface.WriteMe/)
+      end
+    end
   end
 
   # https://github.com/mvidner/ruby-dbus/pull/19
@@ -54,10 +73,6 @@
     expect(@iface["ReadOrWriteMe"]).to eq("VALUE")
   end
 
-  it "tests property nonwriting" do
-    expect { @iface["ReadMe"] = "WROTE" }.to raise_error(DBus::Error, /not writable/)
-  end
-
   it "tests get all" do
     all = @iface.all_properties
     expect(all.keys.sort).to eq(["MyArray", "MyByte", "MyDict", "MyStruct", "MyVariant", "ReadMe", "ReadOrWriteMe"])