Report which Pester.BeforeContainer.ps1 files applied to a container

src/Pester.Runtime.ps1

@@ -1029,6 +1029,11 @@ function Invoke-ContainerDiscovery {
     # set correctly as if we provided -Data to New-Block
     $root.Data = $Container.Data
 
+    # Record which Pester.BeforeContainer.ps1 files applied, so the result says where a
+    # container's setup came from. The folder tree alone does not answer it, #pester:no-inherit
+    # can cut the chain short.
+    $root.BeforeContainerFile = [System.Collections.Generic.List[string]]@($BeforeContainerFile)
+
     Reset-PerContainerState -RootBlock $root
 
     $steps = $state.Plugin.ContainerDiscoveryStart

src/csharp/Pester/Block.cs

@@ -57,6 +57,10 @@ public Block()
         public string ItemType { get; } = "Block";
 
         public ContainerInfo BlockContainer { get; set; }
+        // Every Pester.BeforeContainer.ps1 that applied to this container, outermost first.
+        // Reading the folder tree is not enough to work this out, because #pester:no-inherit can
+        // cut the chain short.
+        public List<string> BeforeContainerFile { get; set; } = new List<string>();
         public object Root { get; set; }
         public bool IsRoot { get; set; }
         public object Parent { get; set; }

src/csharp/Pester/Container.cs

@@ -34,7 +34,8 @@ public static Container CreateFromBlock (Block block) {
                 Item = block.BlockContainer.Item,
                 Blocks = block.Blocks,
                 Data = block.Data,
-                StandardOutput = block.StandardOutput
+                StandardOutput = block.StandardOutput,
+                BeforeContainerFile = block.BeforeContainerFile
         };
         }
 
@@ -56,6 +57,9 @@ public string Type
         }
         public object Item { get; set; }
         public object Data { get; set; }
+        // Every Pester.BeforeContainer.ps1 that applied to this container, outermost first, so
+        // "where did this function come from" is answerable from the result object.
+        public List<string> BeforeContainerFile { get; set; } = new List<string>();
         public List<Block> Blocks { get; set; } = new List<Block>();
         public string Result { get; set; } = "NotRun";
         public TimeSpan Duration { get => DiscoveryDuration + UserDuration + FrameworkDuration; }

tst/Pester.RSpec.Parallel.ts.ps1

@@ -479,6 +479,54 @@ Describe 'Second' {
             finally { Remove-Item -Path $folder -Recurse -Force }
         }
 
+        t "reports which Pester.BeforeContainer.ps1 files applied to each container" {
+            # The folder tree alone does not answer this, #pester:no-inherit can cut the chain
+            # short, so the applied files are on the container. (#3007)
+            $folder = New-CascadingBeforeContainerFolder
+            try {
+                $c = [PesterConfiguration]::Default
+                $c.Run.Path = $folder
+                $c.Run.RepoRoot = $folder
+                $c.Run.PassThru = $true
+                $c.Output.Verbosity = 'None'
+                $r = Invoke-Pester -Configuration $c
+
+                $r.FailedCount | Verify-Equal 0
+
+                $unit = $r.Containers | Where-Object { $_.Item.FullName -like '*unit*' }
+                $integration = $r.Containers | Where-Object { $_.Item.FullName -like '*integration*' }
+
+                # unit sees root + tests + unit, integration sees root + tests, outermost first.
+                $unit.BeforeContainerFile.Count | Verify-Equal 3
+                $integration.BeforeContainerFile.Count | Verify-Equal 2
+                (Split-Path $unit.BeforeContainerFile[0] -Parent) | Verify-Equal $folder
+            }
+            finally { Remove-Item -Path $folder -Recurse -Force }
+        }
+
+        t "reports only the files that survived #pester:no-inherit" {
+            $folder = New-NoInheritBeforeContainerFolder
+            try {
+                $c = [PesterConfiguration]::Default
+                $c.Run.Path = $folder
+                $c.Run.RepoRoot = $folder
+                $c.Run.PassThru = $true
+                $c.Output.Verbosity = 'None'
+                $r = Invoke-Pester -Configuration $c
+
+                $r.FailedCount | Verify-Equal 0
+
+                $docs = $r.Containers | Where-Object { $_.Item.FullName -like '*docs*' }
+                $normal = $r.Containers | Where-Object { $_.Item.FullName -notlike '*docs*' }
+
+                # docs cut the chain, so it reports only its own file, not the root one.
+                $docs.BeforeContainerFile.Count | Verify-Equal 1
+                $normal.BeforeContainerFile.Count | Verify-Equal 1
+                (Split-Path $docs.BeforeContainerFile[0] -Parent) | Verify-Equal (Join-Path $folder 'docs')
+            }
+            finally { Remove-Item -Path $folder -Recurse -Force }
+        }
+
         t "does not overwrite a Run.RepoRoot the user set" {
             # A real directory. Resolving the chain runs the value through GetFullPath, and a made
             # up path is not portable: on Windows something like 'TestDrive:whatever' reads as a