Use FormatMessage for exception messages in cases where the stowed/language exception doesn't contain a message #2022

ahmed605 · 2025-07-23T11:56:21Z

Updated HRESULT to Exception conversion logic to fall back to system-formatted error messages via the Win32 FormatMessage API when custom error text is not available or is blank. This ensures more consistent and informative exception messages by leveraging Windows' built-in error descriptions.

Example:

…nguage exception doesn't contain a message

ahmed605 · 2025-07-23T11:58:00Z

@riverar

manodasanW · 2025-07-23T23:49:15Z

Thanks for the change, kicked off CI.

ahmed605 · 2025-07-24T11:18:49Z

are the CI failures related to the PR? GitHub doesn't allow me to see the details of them

riverar

Can we get a test for this too? Ideally one that runs RPC_E_WRONG_THREAD through this helper to ensure it spits out the right message.

src/WinRT.Runtime/ExceptionHelpers.cs

src/WinRT.Runtime/Platform.cs

riverar · 2025-07-24T17:34:23Z

Think we should also clean up the commit message on merge (this is not related to WinRT Originate errors) and add a proper PR description here for our future selves looking back at this change.

Perhaps something like:

Updated HRESULT to Exception conversion logic to fall back to system-formatted error messages via the Win32 FormatMessage API when custom error text is not available or is blank. This ensures more consistent and informative exception messages by leveraging Windows' built-in error descriptions.

manodasanW · 2025-07-25T05:55:20Z

are the CI failures related to the PR? GitHub doesn't allow me to see the details of them

No, it is unrelated. Have a PR to fix it, after it is merged, you can rebase your changes.

…ce to check for empty error messages

manodasanW · 2025-07-25T19:31:36Z

Is there any test that we can add here to confirm we get expected message for a certain HRESULT.

dongle-the-gadget · 2025-07-26T01:41:49Z

Isn't it enough that we test the ExceptionHelpers class itself? I don't see why we need to wind up WinRT to test it.

In addition, I think we should test if the message is not empty, rather than requiring a string match, because error messages might be localized.

riverar · 2025-07-26T04:05:10Z

I'd still check the error message when possible to ensure we're not getting garbage. Can wrap it in a conditional so that non en-US developers don't break. If that's not a concern for this project, I'd delete the en-US check.

[Fact]
public void TestGetExceptionForHR_WithValidHResult_ReturnsSystemFormattedException()
{
    // Arrange
    const int RPC_E_WRONG_THREAD = unchecked((int)0x8001010E);

    // Act
    Exception exception = ExceptionHelpers.GetExceptionForHR(RPC_E_WRONG_THREAD);

    // Assert
    Assert.NotNull(exception);
    Assert.False(string.IsNullOrWhiteSpace(exception.Message));
    if (CultureInfo.CurrentUICulture.Name == "en-US")
    {
        Assert.Equal("The application called an interface that was marshalled for a different thread. (0x8001010E)", exception.Message);
    }
}

I can't test this for you because the build fails despite following the on-boarding instructions.

ahmed605 · 2025-07-26T13:35:48Z

I'd still check the error message when possible to ensure we're not getting garbage. Can wrap it in a conditional so that non en-US developers don't break. If that's not a concern for this project, I'd delete the en-US check.

[Fact]
public void TestGetExceptionForHR_WithValidHResult_ReturnsSystemFormattedException()
{
    // Arrange
    const int RPC_E_WRONG_THREAD = unchecked((int)0x8001010E);

    // Act
    Exception exception = ExceptionHelpers.GetExceptionForHR(RPC_E_WRONG_THREAD);

    // Assert
    Assert.NotNull(exception);
    Assert.False(string.IsNullOrWhiteSpace(exception.Message));
    if (CultureInfo.CurrentUICulture.Name == "en-US")
    {
        Assert.Equal("The application called an interface that was marshalled for a different thread. (0x8001010E)", exception.Message);
    }
}

I can't test this for you because the build fails despite following the on-boarding instructions.

added (and tested) this, and I can confirm that building and running the UnitTest project was painful

…release.251115.2 (#4204) This PR contains the following updates: | Package | Change | [Age](https://docs.renovatebot.com/merge-confidence/) | [Confidence](https://docs.renovatebot.com/merge-confidence/) | |---|---|---|---| | [Microsoft.Windows.CsWinRT](https://redirect.github.com/microsoft/cswinrt) | `2.3.0-prerelease.251015.2` -> `2.3.0-prerelease.251115.2` | ![age](https://developer.mend.io/api/mc/badges/age/nuget/Microsoft.Windows.CsWinRT/2.3.0-prerelease.251115.2?slim=true) | ![confidence](https://developer.mend.io/api/mc/badges/confidence/nuget/Microsoft.Windows.CsWinRT/2.3.0-prerelease.251015.2/2.3.0-prerelease.251115.2?slim=true) | --- ### Release Notes <details> <summary>microsoft/cswinrt (Microsoft.Windows.CsWinRT)</summary> ### [`v2.3.0-prerelease.251115.2`](https://redirect.github.com/microsoft/CsWinRT/releases/tag/2.3.0-prerelease.251115.2): CsWinRT 2.3.0-prerelease.251115.2 This is a prerelease version of C#/WinRT with more bug fixes and improvements. **C#/WinRT package**: <https://www.nuget.org/packages/Microsoft.Windows.CsWinRT/2.3.0-prerelease.251115.2> #### What's Changed - Fix warning by [@manodasanW](https://redirect.github.com/manodasanW) in [microsoft/CsWinRT#2023](https://redirect.github.com/microsoft/CsWinRT/pull/2023) - Use FormatMessage for exception messages in cases where the stowed/language exception doesn't contain a message by [@ahmed605](https://redirect.github.com/ahmed605) in [microsoft/CsWinRT#2022](https://redirect.github.com/microsoft/CsWinRT/pull/2022) - Merge to staging/2.3 by [@manodasanW](https://redirect.github.com/manodasanW) in [microsoft/CsWinRT#2025](https://redirect.github.com/microsoft/CsWinRT/pull/2025) - Merge staging/2.3 to master by [@manodasanW](https://redirect.github.com/manodasanW) in [microsoft/CsWinRT#2030](https://redirect.github.com/microsoft/CsWinRT/pull/2030) - Fix 'Initialize' typo in several files by [@Lightczx](https://redirect.github.com/Lightczx) in [microsoft/CsWinRT#2035](https://redirect.github.com/microsoft/CsWinRT/pull/2035) - Fix design time build error causing incremental build issue by [@manodasanW](https://redirect.github.com/manodasanW) in [microsoft/CsWinRT#2036](https://redirect.github.com/microsoft/CsWinRT/pull/2036) - Move TestWinRT repo clone to resource by [@manodasanW](https://redirect.github.com/manodasanW) in [microsoft/CsWinRT#2032](https://redirect.github.com/microsoft/CsWinRT/pull/2032) - Fix weak reference rehydration scenarios for non projected types by [@manodasanW](https://redirect.github.com/manodasanW) in [microsoft/CsWinRT#2043](https://redirect.github.com/microsoft/CsWinRT/pull/2043) - Add UpToDateCheckBuilt to cover incremental build of Implementation dlls by [@jevansaks](https://redirect.github.com/jevansaks) in [microsoft/CsWinRT#2051](https://redirect.github.com/microsoft/CsWinRT/pull/2051) - Fix issue where IReferenceArray is not being found by [@manodasanW](https://redirect.github.com/manodasanW) in [microsoft/CsWinRT#2071](https://redirect.github.com/microsoft/CsWinRT/pull/2071) - Fix issue with unsubscribing from events on non-agile objects by [@manodasanW](https://redirect.github.com/manodasanW) in [microsoft/CsWinRT#2079](https://redirect.github.com/microsoft/CsWinRT/pull/2079) - Fix issues with CopyToManagedArray by [@manodasanW](https://redirect.github.com/manodasanW) in [microsoft/CsWinRT#2084](https://redirect.github.com/microsoft/CsWinRT/pull/2084) #### New Contributors - [@ahmed605](https://redirect.github.com/ahmed605) made their first contribution in [microsoft/CsWinRT#2022](https://redirect.github.com/microsoft/CsWinRT/pull/2022) - [@Lightczx](https://redirect.github.com/Lightczx) made their first contribution in [microsoft/CsWinRT#2035](https://redirect.github.com/microsoft/CsWinRT/pull/2035) **Full Changelog**: <microsoft/CsWinRT@2.3.0-prerelease.250720.1...2.3.0-prerelease.251115.2> </details> --- ### Configuration 📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined). 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this PR and you won't be reminded about this update again. --- - [ ] If you want to rebase/retry this PR, check this box --- This PR was generated by [Mend Renovate](https://mend.io/renovate/). View the [repository job log](https://developer.mend.io/github/reactiveui/ReactiveUI).  Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

use FormatMessage for exception messages in cases where the stowed/la…

f4407fd

…nguage exception doesn't contain a message

use HRESULT code as an exception message as a last resort

0e88488

riverar reviewed Jul 24, 2025

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src/WinRT.Runtime/ExceptionHelpers.cs Outdated Show resolved Hide resolved

src/WinRT.Runtime/Platform.cs Outdated Show resolved Hide resolved

ahmed605 and others added 2 commits July 25, 2025 11:37

use lowercase kernel32.dll DllImports and use string.IsNullOrWhiteSpa…

edadf8d

…ce to check for empty error messages

Merge branch 'master' into ahmed605/exception-messages

0081d29

Add test for system formatted exception messages

6841ea2

manodasanW approved these changes Jul 26, 2025

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manodasanW merged commit b50e31e into microsoft:master Jul 26, 2025
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Use FormatMessage for exception messages in cases where the stowed/language exception doesn't contain a message #2022

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Use FormatMessage for exception messages in cases where the stowed/language exception doesn't contain a message #2022

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