Unhandled exception: System.Exception: Restore operation failed.

[Daniel Hughes]

The below exception occurred in our ci when running dotnet format:

dotnet format --verify-no-changes

Unhandled exception: System.Exception: Restore operation failed.
at Microsoft.CodeAnalysis.Tools.CodeFormatter.OpenMSBuildWorkspaceAsync(String solutionOrProjectPath, WorkspaceType workspaceType, Boolean noRestore, Boolean requiresSemantics, String binaryLogPath, Boolean logWorkspaceWarnings, ILogger logger, CancellationToken cancellationToken)
at Microsoft.CodeAnalysis.Tools.CodeFormatter.FormatWorkspaceAsync(FormatOptions formatOptions, ILogger logger, CancellationToken cancellationToken, String binaryLogPath)
at Microsoft.CodeAnalysis.Tools.FormatCommandCommon.FormatAsync(FormatOptions formatOptions, ILogger`1 logger, CancellationToken cancellationToken)
at Microsoft.CodeAnalysis.Tools.Commands.RootFormatCommand.FormatCommandDefaultHandler.InvokeAsync(InvocationContext context)
at System.CommandLine.Invocation.InvocationPipeline.<>c__DisplayClass4_0.<b__0>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.CommandLineBuilderExtensions.<>c__DisplayClass16_0.<b__0>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.CommandLineBuilderExtensions.<>c__DisplayClass11_0.<b__0>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.CommandLineBuilderExtensions.<>c__DisplayClass21_0.<b__0>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.CommandLineBuilderExtensions.<>c__DisplayClass18_0.<b__0>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.CommandLineBuilderExtensions.<>c.<b__17_0>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.CommandLineBuilderExtensions.<>c__DisplayClass15_0.<b__0>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.CommandLineBuilderExtensions.<>c.<b__4_0>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.CommandLineBuilderExtensions.<>c__DisplayClass7_0.<b__0>d.MoveNext()

This exception doesn't really tell us anything. It uses System.Exception rather than a more specific type. And the message "Restore operation failed" doesn't tell us why it failed/what specifically went wrong when doing the restore operation.

[Daniel Hughes]

It looks like PerformRestoreAsync is the issue, it doesn't capture the stdout/stderr of dotnet restore. So doesn't know what the issue was.