Fix potential unobserved exception in InputHandler.cs

[ycholette]

Observable.Do() does not catch exceptions from FromAsync(), resulting in a potential unobserved exception.

[dnfadmin]

All CLA requirements met.

[codecov]

Codecov Report

Merging #635 (999977f) into master (5281160) will decrease coverage by 3.54%.
The diff coverage is 100.00%.

❗ Current head 999977f differs from pull request most recent head e70890d. Consider uploading reports for the commit e70890d to get more accurate results

@@            Coverage Diff             @@
##           master     #635      +/-   ##
==========================================
- Coverage   72.89%   69.34%   -3.55%     
==========================================
  Files         257      257              
  Lines       12576    12583       +7     
  Branches      848      848              
==========================================
- Hits         9167     8726     -441     
- Misses       3409     3587     +178     
- Partials        0      270     +270     

Impacted Files	Coverage Δ
src/JsonRpc/InputHandler.cs	85.33% <100.00%> (-3.98%)	⬇️
src/JsonRpc/ExternalServiceProvider.cs	50.00% <0.00%> (-50.00%)	⬇️
src/JsonRpc.Generators/SymbolExtensions.cs	71.42% <0.00%> (-28.58%)	⬇️
src/JsonRpc/Server/ContentModifiedException.cs	37.50% <0.00%> (-18.75%)	⬇️
src/JsonRpc/Server/RequestCancelledException.cs	37.50% <0.00%> (-18.75%)	⬇️
...rver/Configuration/ChainedConfigurationProvider.cs	58.62% <0.00%> (-17.25%)	⬇️
...ient/Configuration/ChainedConfigurationProvider.cs	0.00% <0.00%> (-17.25%)	⬇️
...rver/Configuration/ChainedConfigurationProvider.cs	0.00% <0.00%> (-17.25%)	⬇️
src/JsonRpc/Server/ServerErrorResult.cs	83.33% <0.00%> (-16.67%)	⬇️
src/JsonRpc.Generators/Contexts/SyntaxSymbol.cs	75.00% <0.00%> (-16.67%)	⬇️
... and 97 more

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[david-driscoll]

Is there an example case where you're seeing this as an issue?

Is there any docs or source you can point to? I would have assumed any exception would just go to the error flow.

[ycholette]

I think this is related to this: dotnet/reactive#1256
Basically, the cancelation token was cancelled, _pipeReader.AdvanceTo(buffer.Start, buffer.End) threw an exception (before the check on the token), and the exception was not observed by anyone. My break point in the Do() never hit.

[david-driscoll]

Alright, that makes a little more sense! Thanks!