"__built-in-schema.yml (Line: 2012, Col: 24): Expected a mapping" after V2-V3 pipeline converstion - msbuild

Question

UPDATE: Here's the contents of azure_pipelines.yml:
resources:
repositories:
- repository: pf
type: git
name: _
ref: refs/tags/3.6.6
trigger: none
stages:
- template: __
parameters:
project:
- name: "__" # Must be unique within the list of projects
type: "msbuild" # Used with Publish/Deploy. Options: adla, dacpac, dotnet, egg, maven, msbuild, node, nuget, python, sap, ssis
path: "__" # Project Path
file: "__.csproj" # Project file
toolset: "msbuild" # Used with Build/Package. Options: adla, dotnet, maven, msbuild, node, python, sap, ssis
playbook: "___.yml"
sonarqube:
name: scan
scan: true
sqExclusions: ""
additionalProperties: "" #|
# sonar.branch.name=master
# sonar.branch.target=master
fortify:
fortifyApp: "_______"
fortifyVersion: "____"
sast: true
dast: false
buildConfiguration: $(BuildConfiguration) #release, debug
buildPlatform: $(BuildPlatform) #any cpu, x86, x64
- name: "__" # Must be unique within the list of projects
type: "msbuild" # Used with Publish/Deploy. Options: adla, dacpac, dotnet, egg, maven, msbuild, node, nuget, python, sap, ssis
path: "___" # Project Path
file: "___.csproj" # Project file
toolset: "msbuild" # Used with Build/Package. Options: adla, dotnet, maven, msbuild, node, python, sap, ssis
playbook: "_.yml"
sonarqube:
name: scan
scan: true
sqExclusions: ""
additionalProperties: "" #|
# sonar.branch.name=master
# sonar.branch.target=master
fortify:
fortifyApp: "______"
fortifyVersion: "__"
sast: true
dast: false
buildConfiguration: $(BuildConfiguration) #release, debug
buildPlatform: $(BuildPlatform) #any cpu, x86, x64
I'm attempting to run the ADO pipeline for a .NET Framework 4.7 app that has undergone the V2 to V3 pipeline conversion. I get the following error message, and the build doesn't even try to run:
__built-in-schema.yml: Maximum object depth exceeded
__built-in-schema.yml (Line: 2012, Col: 24): Expected a mapping
__built-in-schema.yml: Maximum object depth exceeded
That's using the msbuild toolset. I have an API project and a web app project in the solution, so if I removed either of them and then run the pipeline, it progresses past this stage, but gets hung on another error. (Not really necessary to go into detail about that error though, because it's directly related to me having removed the other project).
With the dotnet toolset, it runs, but then complains about a missing reference:
> D:\a\1\s\___\___.csproj(350,3): error MSB4019: The imported project "C:\Program Files\dotnet\sdk\3.1.101\Microsoft\VisualStudio\v16.0\WebApplications\Microsoft.WebApplication.targets" was not found. Confirm that the expression in the Import declaration "C:\Program Files\dotnet\sdk\3.1.101\Microsoft\VisualStudio\v16.0\WebApplications\Microsoft.WebApplication.targets" is correct, and that the file exists on disk.
0 Warning(s)
I've tried commenting out the reference to Microsoft.WebApplication.targets in the .csproj files for the app, but it just adds them back in when I run the build locally or via the pipeline.
I've also tried changing the build pool to VS 2017 and Hosted Windows 2019 with VS2019, thinking the VS targets would be available in those pools, but no luck.
I also tried installing MSBuild.Microsoft.VisualStudio.Web.targets via NuGet, but end up with the same results.
What am I missing here?

Answer 1

“__built-in-schema.yml (Line: 2012, Col: 24): Expected a mapping” after V2-V3 pipeline converstion
According to the error log:
error MSB4019: The imported project "C:\Program
Files\dotnet\sdk\3.1.101\Microsoft\VisualStudio\v16.0\WebApplications\Microsoft.WebApplication.targets"
was not found
We could to know the Microsoft.WebApplication.targets invoked from dotnet SDK instead of MSBuild. The correct path for Microsoft.WebApplication.targets should be:
C:\Program Files (x86)\Microsoft Visual Studio\2019\Professional\MSBuild\Microsoft\VisualStudio\v16.0\WebApplications\Microsoft.WebApplication.targets
So, we need use MSBuild toolset instead of the dotnet toolset. And since it use the MSBuild 16.0, we need use the build agent pool Hosted Windows 2019 with VS2019 to build the project.
For the error Maximum object depth exceeded, it seems your yaml file has too deep file path, please try to shortening the file path to see if this resolves the issue.
If above info not help you, please share more info about you issue, like what is your project type, is python project? And share your build pipeline (yaml).
Hope this helps.