T34: prompts and commands carry OSC 133 marks: the tap reads every OSC body and hands 133's marks to the session, which keeps its last command's status; zsh, bash, fish and PowerShell mark what the shell leaves unmarked, and the user's prompt still sees the status

assets/shell-integration/pwsh/elyterminal.ps1

@@ -1,6 +1,23 @@
-# ELYTerminal: wrap the prompt to report folder and title.
+# ELYTerminal: wrap the prompt to report folder and title and to mark prompts and commands.
 $global:ElyPrompt = $function:prompt
+$global:ElyRan = $false
 function global:prompt {
+    # First: every statement sets $? again.
+    $ok = $?
+    $esc, $bel = [char]27, [char]7
+    if ($global:ElyRan) {
+        $code = 1
+        if ($ok) { $code = 0 }
+        elseif ($Error.Count -eq 0 -or [object]::ReferenceEquals($Error[0], $global:ElyError)) {
+            # No new error: a native program failed. Strict mode refuses an unset variable.
+            $code = Get-Variable LASTEXITCODE -Scope Global -ValueOnly -ErrorAction Ignore
+        }
+        [Console]::Write("$esc]133;D;$code$bel")
+        $global:ElyRan = $false
+    }
+    [Console]::Write("$esc]133;A$bel")
+    # The user's prompt sees a failed command's $? still.
+    if (-not $ok) { Write-Error '' -ErrorAction Ignore }
     $text = & $global:ElyPrompt
     $folder = $executionContext.SessionState.Path.CurrentLocation
     if ($folder.Provider.Name -eq 'FileSystem') {
@@ -8,8 +25,20 @@ function global:prompt {
         $path = ($parts | ForEach-Object { [Uri]::EscapeDataString($_) }) -join '/'
         if (-not $path.StartsWith('/')) { $path = "/$path" }
         $leaf = (Split-Path -Leaf $folder.ProviderPath) -replace '\p{Cc}', ''
-        $esc, $bel = [char]27, [char]7
         [Console]::Write("$esc]7;file://$path$bel$esc]2;$leaf$bel")
     }
-    $text
+    "$text$esc]133;B$bel"
+}
+# A command starts once PSReadLine hands over a line that is not blank.
+if (Test-Path Function:\PSConsoleHostReadLine) {
+    $global:ElyReadLine = $function:PSConsoleHostReadLine
+    function global:PSConsoleHostReadLine {
+        $line = & $global:ElyReadLine
+        if (-not [string]::IsNullOrWhiteSpace($line)) {
+            $global:ElyRan = $true
+            $global:ElyError = if ($Error.Count) { $Error[0] }
+            [Console]::Write("$([char]27)]133;C$([char]7)")
+        }
+        $line
+    }
 }