Race condition in ExtensionsMetadataGenerator.targets leads to incorrect TargetDir

[moritonal]

Investigative information

• Timestamp: As of 05 Feb 2019
• Function App version (1.0 or 2.0): 2.0
• Function App name: N/A
• Function name(s) (as appropriate): N/A
• Invocation ID: N/A
• Region: N/A

Repro steps

Referencing Microsoft.Azure.WebJobs.Script.ExtensionsMetadataGenerator should create an extensions.json file within our TargetDir. Currently, referencing both this, and Microsoft.Net.SDK.Functions leads to the incorrect TargetDir being used in the Generation part of this project.

Expected behavior

The file extensions.json should be generated in the correct TargetDir directory, with the correct values.

Actual behavior

A variety of things happen depending on the specific order of events, but most resolve into an empty extensions.json file being outputted somewhere.

Known workarounds

Putting a custom .targets file within your project.

Related information

I'm fairly sure this is the cause of a lot of issues given I believe (of course I could be wrong) this bug is referenced in the following:

• "No job functions found" after updating to 2.0.12050.0 Azure-Functions#928 (comment)
• Azure function Publish not creating Startup class entry in extensions.json Azure-Functions#972
• https://stackoverflow.com/questions/52583637/azure-function-publish-not-creating-startup-class-entry-in-extensions-json
• Functions using custom extensions work in emulator but fail indexing when deployed (c#, v2.0.12050.0) #3386
• Not working with Microsoft.Extensions.DependencyInjection v2.2.0 BorisWilhelms/azure-function-dependency-injection#26
• error "No job functions found" when trying to run functions locally chopeen/last-fm-not-mine-alert-func#5
• ExtensionsMetadataGenerator does not include function defined WebJobStartupAttribute azure-functions-core-tools#721
• extension.json not generating consistenly Azure-Functions#957

I have a pull-request which I'll attach shortly.

The issue is mostly caused by https://github.com/Azure/azure-functions-vs-build-sdk/blob/master/src/Microsoft.NET.Sdk.Functions.MSBuild/Targets/netstandard1.0/Microsoft.NET.Sdk.Functions.Build.targets#150 changing the TargetPath which (given the Property's in the current Extension.Targets are set at start) means that the ConsoleApp within ExtensionsMetadataGenerator executes over the wrong directory.

[moritonal]

Closing because I've used the incorrect account, see #4057