Show specific error message for `dotnet <app_path>` where app_path is a non-dll/exe file that exists #116940

Copilot · 2025-06-23T22:44:37Z

Currently, when a user runs dotnet <app_path> and the host determines that <app_path> is not a runnable app, it's treated as a CLI command and routed to the SDK, which shows a generic error message.

This PR improves the user experience by detecting when the user passes a path to an existing non-dll/exe file and showing a specific error message instead of routing to the SDK.

cc @dotnet/appmodel @AaronRobinsonMSFT

Changes Made

Core Logic Enhancement:

Enhanced argument parsing in command_line.cpp to detect the specific scenario:
- File is not managed (.dll/.exe)
- Path contains directory separator
- File exists
- Not in exec mode
Added specific error message for the above

Behavior Change:

Before:

$ dotnet /path/to/config.json
Could not execute because the specified command or file was not found.
Possible reasons for this include:
  You misspelled a built-in dotnet command.
  You intended to execute a .NET program, but dotnet-/path/to/config.json does not exist.
  You intended to run a global tool, but a dotnet-prefixed executable with this name could not be found on the PATH.

After:

$ dotnet /path/to/config.json
The application '/path/to/config.json' does not exist or is not a managed .dll or .exe.

Preserves Existing Behavior:

Commands without directory separators (like dotnet build) still route to SDK
dotnet exec behavior unchanged
All existing error codes and messages unchanged

Test Coverage

Added comprehensive tests covering:

Absolute paths with directory separators
Relative paths like ./subdir/file.txt
Commands without separators still route to SDK
Backward compatibility verification

All existing tests pass, confirming no regressions.

Fixes #116939.

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

… separators Co-authored-by: elinor-fung <47805090+elinor-fung@users.noreply.github.com>

Co-authored-by: elinor-fung <47805090+elinor-fung@users.noreply.github.com>

jkotas · 2025-06-23T23:51:47Z

src/native/corehost/fxr/fx_muxer.cpp

@@ -572,6 +572,11 @@ int fx_muxer_t::execute(
            return result;
        }
    }
+    else if (static_cast<StatusCode>(result) == AppArgNotManagedFailure)
+    {
+        trace::error(_X("The application '%s' does not exist or is not a managed .dll or .exe."), app_candidate.c_str());


Suggested change

trace::error(_X("The application '%s' does not exist or is not a managed .dll or .exe."), app_candidate.c_str());

trace::error(_X("The application '%s' is not a managed .dll or .exe."), app_candidate.c_str());

This error code is returned above only when the file actually exists

Updated the error message to remove "does not exist or" since this error code is only returned when the file actually exists. Changes committed in d2dd638.

…reporting Co-authored-by: jkotas <6668460+jkotas@users.noreply.github.com>

src/native/corehost/fxr/command_line.cpp

…error directly in command_line.cpp Co-authored-by: elinor-fung <47805090+elinor-fung@users.noreply.github.com>

src/installer/tests/HostActivation.Tests/DotnetArgValidation.cs

test.txt

…tions, remove test file Co-authored-by: elinor-fung <47805090+elinor-fung@users.noreply.github.com>

src/native/corehost/fxr/command_line.cpp

Co-authored-by: elinor-fung <47805090+elinor-fung@users.noreply.github.com>

src/installer/tests/HostActivation.Tests/DotnetArgValidation.cs

Co-authored-by: elinor-fung <47805090+elinor-fung@users.noreply.github.com>

am11 · 2025-06-29T16:37:56Z

i wonder how much co2 was released into the air just for this

On the bright side, Copilot gets smarter for future PRs. Plus, CO₂ in its supercritical form has some surprising uses, like powering sCO₂ turbines for electricity. So hey, not all doom and gloom on the hippie’s fry! ✌️

am11 · 2025-06-29T17:49:34Z

the temperatures keep rising and carbon capture is a scam to distract the population from the rampant use of polluting technologies, and no, an LLM cannot get "smarter", its a glorified markov chain with no cognitive processes.

Carbon capture has legitimate applications if used alongside real emissions cuts. And LLMs are far beyond Markov chains, they learn complex patterns across context, not just next-word guessing.

jkotas · 2025-07-01T20:06:50Z

src/native/corehost/fxr/command_line.cpp

+                    {
+                        if (pal::file_exists(app_candidate))
+                        {
+                            trace::error(_X("The application '%s' is not a managed .dll or .exe."), app_candidate.c_str());


Suggested change

trace::error(_X("The application '%s' is not a managed .dll or .exe."), app_candidate.c_str());

trace::error(_X("The application '%s' is not a managed .dll."), app_candidate.c_str());

I do not think managed .exes are a thing in modern .NET. None of the tooling will produce them. Should we drop or .exe here to avoid suggesting that managed .exes are a thing?

Alternatively, we can say `is not a .NET binary.". "binary" looks less Windows-specific, but also less descriptive. It won't give you a hint that you need to pass in .dll.

Changed to "is not a managed .dll." as suggested. You're right that managed .exe files aren't really a thing in modern .NET. Updated both the error message and the corresponding test. Changes committed in fdf2d2d.

Co-authored-by: jkotas <6668460+jkotas@users.noreply.github.com>

elinor-fung · 2025-07-02T00:32:10Z

src/installer/tests/HostActivation.Tests/FrameworkDependentAppLaunch.cs

@@ -58,7 +58,7 @@ public void Muxer_AssemblyWithDifferentFileExtension_Fails()
                .CaptureStdErr()
                .Execute()
                .Should().Fail()
-                .And.HaveStdErrContaining($"The application '{appOtherExt}' does not exist or is not a managed .dll or .exe");
+                .And.HaveStdErrContaining($"The application '{appOtherExt}' is not a managed .dll or .exe");


Suggested change

.And.HaveStdErrContaining($"The application '{appOtherExt}' is not a managed .dll or .exe");

.And.HaveStdErrContaining($"The application '{appOtherExt}' is not a managed .dll.");

Updated the test assertion to match the corrected error message format. Changes committed in 570590e.

Co-authored-by: elinor-fung <47805090+elinor-fung@users.noreply.github.com>

Initial plan for issue

f26ba83

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Implement specific error message for non-managed files with directory…

f7d5ee5

… separators Co-authored-by: elinor-fung <47805090+elinor-fung@users.noreply.github.com>

Fix error codes to avoid shifting existing codes and breaking tests

940ff2b

Co-authored-by: elinor-fung <47805090+elinor-fung@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Show specific error message for dotnet <app_path> where <app_path> is a non-dll/exe file that exists~~ Show specific error message for dotnet <app_path> where app_path is a non-dll/exe file that exists Jun 23, 2025

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Show specific error message for `dotnet <app_path>` where app_path is a non-dll/exe file that exists #116940

Show specific error message for `dotnet <app_path>` where app_path is a non-dll/exe file that exists #116940

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edited by elinor-fung

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	trace::error(_X("The application '%s' does not exist or is not a managed .dll or .exe."), app_candidate.c_str());
	trace::error(_X("The application '%s' is not a managed .dll or .exe."), app_candidate.c_str());

	.And.HaveStdErrContaining($"The application '{appOtherExt}' is not a managed .dll or .exe");
	.And.HaveStdErrContaining($"The application '{appOtherExt}' is not a managed .dll.");

Show specific error message for dotnet <app_path> where app_path is a non-dll/exe file that exists #116940

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Show specific error message for `dotnet <app_path>` where app_path is a non-dll/exe file that exists #116940

Show specific error message for `dotnet <app_path>` where app_path is a non-dll/exe file that exists #116940

Copilot AI commented Jun 23, 2025 •

edited by elinor-fung

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