Unable to read ReadOnly Encoder

Technical
1

Hello everyone,

I’m working on deploying a custom GUI with bunch of custom-made wrappers for serial hardware. All of the wrappers are working when I use TUI, and my basic and comparison steps seem to be working just fine when I use my custom GUI. However, I am getting this weird set of errors about the encoder.

Serializer ; Error ; XML Line 7: Unable to read EncoderReplacementFallback. Instance is read-only.

Can anyone tell me what XML this is referring to? Line 7 of the tapplan that the GUI is feeding into OpenTAP is:

<TestStep type="OpenTap.Plugins.BasicSteps.SequenceStep" Id="7180e4ff-6d05-47e7-a598-0fb2ed973fa3">

I’d like to figure out how to fix this Encoder/Decoder problem, as I’m having other issues and trying to ensure that this isn’t causing them.

I’m loading TapPlans from a database. The TapPlans contain multiple references to other TapPlans that have all been “converted to sequence” using the TUI Convert to Sequence option.

Relevant log section is below:

2025-06-30 15:08:35.301057 ; PluginManager  ; Debug       ; Searched 176 Assemblies. [146 ms]
2025-06-30 15:08:35.301545 ; AssemblyData   ; Debug       ; Loaded OpenTap. [163 us]
2025-06-30 15:08:35.301562 ; AssemblyData   ; Debug       ; Loaded OpenTap.Plugins.BasicSteps. [235 us]
2025-06-30 15:08:35.301575 ; AssemblyData   ; Debug       ; Loaded OpenTap.Package. [169 us]
2025-06-30 15:08:35.301725 ; AssemblyData   ; Debug       ; Loaded OpenTap.Python. [157 us]
2025-06-30 15:08:35.326755 ; Python         ; Debug       ; Loading: UsbTmcDevice-Python.TmcInstrument
2025-06-30 15:08:35.327097 ; AssemblyData   ; Debug       ; Loaded . [900 ns]
2025-06-30 15:08:35.327145 ; AssemblyData   ; Debug       ; Loaded . [200 ns]
2025-06-30 15:08:35.327165 ; AssemblyData   ; Debug       ; Loaded . [100 ns]
2025-06-30 15:08:35.327180 ; AssemblyData   ; Debug       ; Loaded . [100 ns]
2025-06-30 15:08:35.327195 ; AssemblyData   ; Debug       ; Loaded . [100 ns]
2025-06-30 15:08:35.328335 ; AssemblyData   ; Debug       ; Loaded . [1.20 us]
2025-06-30 15:08:35.328389 ; Python         ; Debug       ; Loading: UsbTmcDevice.TmcInstrument
2025-06-30 15:08:35.328571 ; AssemblyData   ; Debug       ; Loaded . [300 ns]
2025-06-30 15:08:35.333088 ; AssemblyData   ; Debug       ; Loaded System.Private.CoreLib. [1.60 us]
2025-06-30 15:08:35.342461 ; AssemblyData   ; Debug       ; Loaded AC_Power_Supply. [518 us]
2025-06-30 15:08:35.343767 ; Resolver       ; Debug       ; Found match for RJCP.SerialPortStream, Version=3.0.3.0, Culture=neutral, PublicKeyToken=5f5e7b70c6a74deb in /opt/sts/Packages/SerialInstrument/RJCP.SerialPortStream.dll
2025-06-30 15:08:35.344749 ; Resolver       ; Debug       ; Found match for RJCP.IO.Buffer, Version=0.2.2.0, Culture=neutral, PublicKeyToken=5f5e7b70c6a74deb in /opt/sts/Packages/SerialInstrument/RJCP.IO.Buffer.dll
2025-06-30 15:08:35.347514 ; AssemblyData   ; Debug       ; Loaded SerialInstrument. [184 us]
2025-06-30 15:08:35.359489 ; AssemblyData   ; Debug       ; Loaded RJCP.SerialPortStream. [127 us]
2025-06-30 15:08:35.360512 ; Resolver       ; Debug       ; Found match for RJCP.Diagnostics.Trace, Version=0.2.1.0, Culture=neutral, PublicKeyToken=5f5e7b70c6a74deb in /opt/sts/Packages/SerialInstrument/RJCP.Diagnostics.Trace.dll
2025-06-30 15:08:35.361297 ; Resolver       ; Debug       ; Found match for RJCP.Core.SysCompat, Version=0.2.0.0, Culture=neutral, PublicKeyToken=5f5e7b70c6a74deb in /opt/sts/Packages/SerialInstrument/RJCP.Core.SysCompat.dll
2025-06-30 15:08:35.363618 ; Resolver       ; Debug       ; Found match for RJCP.Core.Environment, Version=0.3.0.0, Culture=neutral, PublicKeyToken=5f5e7b70c6a74deb in /opt/sts/Packages/SerialInstrument/RJCP.Core.Environment.dll
2025-06-30 15:08:35.419777 ; Serializer     ; Error       ; XML Line 7: Unable to read EncoderReplacementFallback. Instance is read-only.
2025-06-30 15:08:35.420966 ; Serializer     ; Debug       ; InvalidOperationException: Instance is read-only.
2025-06-30 15:08:35.421238 ; Serializer     ; Debug       ;     at System.Text.Encoding.set_EncoderFallback(EncoderFallback value)
2025-06-30 15:08:35.421244 ; Serializer     ; Debug       ;     at System.RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor)
2025-06-30 15:08:35.421246 ; Serializer     ; Debug       ;     at System.Reflection.MethodBaseInvoker.InvokeDirectByRefWithFewArgs(Object obj, Span`1 copyOfArgs, BindingFlags invokeAttr)
2025-06-30 15:08:35.423202 ; Serializer     ; Debug       ; Exception caught at:
2025-06-30 15:08:35.424412 ; Serializer     ; Debug       ;     at Void LogMessages()
2025-06-30 15:08:35.424454 ; Serializer     ; Debug       ;     at System.Object Deserialize(System.Xml.Linq.XDocument, OpenTap.ITypeData, Boolean, System.String)
2025-06-30 15:08:35.424466 ; Serializer     ; Debug       ;     at System.Object Deserialize(System.IO.Stream, Boolean, OpenTap.ITypeData, System.String)
2025-06-30 15:08:35.424475 ; Serializer     ; Debug       ;     at OpenTap.ComponentSettings Load(System.Type)
2025-06-30 15:08:35.424502 ; Serializer     ; Debug       ;     ...
2025-06-30 15:08:35.424527 ; Serializer     ; Error       ; XML Line 8: Unable to read DecoderReplacementFallback. Instance is read-only.
2025-06-30 15:08:35.424531 ; Serializer     ; Debug       ; InvalidOperationException: Instance is read-only.
2025-06-30 15:08:35.424605 ; Serializer     ; Debug       ;     at System.Text.Encoding.set_DecoderFallback(DecoderFallback value)
2025-06-30 15:08:35.424606 ; Serializer     ; Debug       ;     at System.RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor)
2025-06-30 15:08:35.424607 ; Serializer     ; Debug       ;     at System.Reflection.MethodBaseInvoker.InvokeDirectByRefWithFewArgs(Object obj, Span`1 copyOfArgs, BindingFlags invokeAttr)
2025-06-30 15:08:35.424735 ; Serializer     ; Debug       ; Exception caught at:
2025-06-30 15:08:35.424778 ; Serializer     ; Debug       ;     at Void LogMessages()
2025-06-30 15:08:35.424780 ; Serializer     ; Debug       ;     at System.Object Deserialize(System.Xml.Linq.XDocument, OpenTap.ITypeData, Boolean, System.String)
2025-06-30 15:08:35.424781 ; Serializer     ; Debug       ;     at System.Object Deserialize(System.IO.Stream, Boolean, OpenTap.ITypeData, System.String)
2025-06-30 15:08:35.424782 ; Serializer     ; Debug       ;     at OpenTap.ComponentSettings Load(System.Type)
2025-06-30 15:08:35.424785 ; Serializer     ; Debug       ;     ...
2025-06-30 15:08:35.424789 ; Serializer     ; Error       ; XML Line 50: Unable to read EncoderReplacementFallback. Instance is read-only.
2025-06-30 15:08:35.424790 ; Serializer     ; Debug       ; InvalidOperationException: Instance is read-only.
2025-06-30 15:08:35.424838 ; Serializer     ; Debug       ;     at System.Text.Encoding.set_EncoderFallback(EncoderFallback value)
2025-06-30 15:08:35.424840 ; Serializer     ; Debug       ;     at InvokeStub_Encoding.set_EncoderFallback(Object, Object, IntPtr*)
2025-06-30 15:08:35.424841 ; Serializer     ; Debug       ;     at System.Reflection.MethodBaseInvoker.InvokeDirectByRefWithFewArgs(Object obj, Span`1 copyOfArgs, BindingFlags invokeAttr)
2025-06-30 15:08:35.424929 ; Serializer     ; Debug       ; Exception caught at:
2025-06-30 15:08:35.424942 ; Serializer     ; Debug       ;     at Void LogMessages()
2025-06-30 15:08:35.424943 ; Serializer     ; Debug       ;     at System.Object Deserialize(System.Xml.Linq.XDocument, OpenTap.ITypeData, Boolean, System.String)
2025-06-30 15:08:35.424944 ; Serializer     ; Debug       ;     at System.Object Deserialize(System.IO.Stream, Boolean, OpenTap.ITypeData, System.String)
2025-06-30 15:08:35.424945 ; Serializer     ; Debug       ;     at OpenTap.ComponentSettings Load(System.Type)
2025-06-30 15:08:35.424946 ; Serializer     ; Debug       ;     ...
2025-06-30 15:08:35.424948 ; Serializer     ; Error       ; XML Line 51: Unable to read DecoderReplacementFallback. Instance is read-only.
2025-06-30 15:08:35.424949 ; Serializer     ; Debug       ; InvalidOperationException: Instance is read-only.
2025-06-30 15:08:35.424973 ; Serializer     ; Debug       ;     at System.Text.Encoding.set_DecoderFallback(DecoderFallback value)
2025-06-30 15:08:35.424974 ; Serializer     ; Debug       ;     at InvokeStub_Encoding.set_DecoderFallback(Object, Object, IntPtr*)
2025-06-30 15:08:35.424976 ; Serializer     ; Debug       ;     at System.Reflection.MethodBaseInvoker.InvokeDirectByRefWithFewArgs(Object obj, Span`1 copyOfArgs, BindingFlags invokeAttr)
2025-06-30 15:08:35.425101 ; Serializer     ; Debug       ; Exception caught at:
2025-06-30 15:08:35.425139 ; Serializer     ; Debug       ;     at Void LogMessages()
2025-06-30 15:08:35.425143 ; Serializer     ; Debug       ;     at System.Object Deserialize(System.Xml.Linq.XDocument, OpenTap.ITypeData, Boolean, System.String)
2025-06-30 15:08:35.425146 ; Serializer     ; Debug       ;     at System.Object Deserialize(System.IO.Stream, Boolean, OpenTap.ITypeData, System.String)
2025-06-30 15:08:35.425149 ; Serializer     ; Debug       ;     at OpenTap.ComponentSettings Load(System.Type)
2025-06-30 15:08:35.425151 ; Serializer     ; Debug       ;     ...

Thanks for your help.

2

Hi @matthewdumas,

I think the problem is that some test step contains information that should not have been serialized. Maybe a setting called EncoderReplacementFallback and DecoderReplacementFallback.

Maybe these should have been ignored with the XmlIgnore attribute or have been internal/private?

3

This is before any test step has been executed.

I’m not sure what XML is being referenced though. Is it the Instruments.xml file, my tapplan, or something else?

4

This comes from a settings file. Maybe you could look through your settings files (Settings) folder and check line 50/51 in all files to see whats there.

5

I’ll do that and report back.

The rest of my issues came from a corrupted database entry. It looks like the data was only half entered in every column for some reason.

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