RegistryValues to the same registries cause LGHT0001

[ElectricErger]

Environment

Version of WiX: 3.11.2.4516
Visual Studio version: Pro 2019 16.7.7
Visual Studio WiX version: 1.0.0.4
.NET version: Framework 4.8.04084

Context

Creating an installer following the "Getting Started" tutorial on FireGiant https://www.firegiant.com/wix/tutorial/getting-started/beyond-files/. Copy and pasted the following from the site verbatim and linked it into my project.

Symptoms

Error message:
Light failure LGHT0001 : Item has already been added. Key in dictionary: <hash> Key being added: <same hash>
Stack trace:

Exception Type: System.ArgumentException

Stack Trace:
   at System.Collections.Hashtable.Insert(Object key, Object nvalue, Boolean add)
   at System.Collections.Hashtable.Add(Object key, Object value)
   at Microsoft.Tools.WindowsInstallerXml.Binder.SetComponentGuids(Output output)
   at Microsoft.Tools.WindowsInstallerXml.Binder.BindDatabase(Output output, String databaseFile)
   at Microsoft.Tools.WindowsInstallerXml.Binder.Bind(Output output, String file)
   at Microsoft.Tools.WindowsInstallerXml.Tools.Light.Run(String[] args)

Turning on Verbose (-v) does not yield any additional details.

Reproduction Steps

When running with the following I get the afforementioned Light error.

<RegistryKey Id='FoobarRegInstallDir' Root='HKLM' Key='Software\Acme\Foobar 1.0' Action='createAndRemoveOnUninstall'>
    <RegistryValue Type='multiString' Name='InstallDir' Value='[TARGETDIR]'/>
    <RegistryValue Type='multiString' Name='InstallDir' Value='[INSTALLDIR]' Action='append'/>
    <RegistryValue Type='multiString' Name='InstallDir' Value='[ProgramFilesFolder]' Action='append'/>
</RegistryKey>

When I changed it up so the RegistryValue used a MultiStringValue the error disappeared and built successfully.

<RegistryValue Type='multiString' Name='myStrings'>
	<MultiStringValue Type='multiString' Name='myStrings' Value='[TARGETDIR]' Action='append' />
	<MultiStringValue Type='multiString' Name='myStrings' Value='[INSTALLDIR]' Action='append'/>
	<MultiStringValue Type='multiString' Name='myStrings' Value='[ProgramFilesFolder]' Action='append'/>
</RegistryValue>

[ElectricErger]

Sorry if this seems benign. I just got caught up with this error for an hour or two and just started renaming symbols until I could track down the hash's component.

[barnson]

Triage: multisz authoring is weird. Can we simplify it to syntactically eliminate this particular error? Rough proposal:

• Eliminate Action
• Add values to Type:
  • multiStringPrepend
  • multiStringAppend
  • Leave multiString to continue to mean overwrite.
  • --or-- add multiStringOverwrite?
• When any multiString type is chosen, Value cannot be used; instead, child MultiString element(s) must be used, even for one value.
• Eliminate MultiStringValue.

Not married or otherwise attached to this design.

[barnson]

Crash is now an actionable error message and tutorial is fixed.

[ElectricErger]

Wow, thanks team!