Fix CLI tab completion for subcommands

packages/darklang/cli/completionPicker.dark

@@ -14,7 +14,10 @@ let create (promptText: String) (items: List<Completion.CompletionItem>) : State
   let parsed = Completion.parseInput promptText
   let commandPrefix =
     if parsed.isCompletingCommand then ""
-    else parsed.commandName ++ " "
+    else
+      let completedArgs = Stdlib.List.dropLast parsed.args
+      let parts = Stdlib.List.append [parsed.commandName] completedArgs
+      (Stdlib.String.join parts " ") ++ " "
 
   State
     { items = items

packages/darklang/cli/config.dark

@@ -81,23 +81,16 @@ let execute (state: Cli.AppState) (args: List<String>) : Cli.AppState =
 
 
 let complete (_state: Cli.AppState) (args: List<String>) : List<Cli.Completion.CompletionItem> =
-  match args with
-  | [] ->
-    ["get"; "set"; "list"]
-    |> Stdlib.List.map Cli.Completion.simple
-
-  | ["get"] ->
+  let configKeys =
     [ "sync.default_instance"
       "sync.interval_seconds"
       "sync.auto_start" ]
-    |> Stdlib.List.map Cli.Completion.simple
-
-  | ["set"] ->
-    [ "sync.default_instance"
-      "sync.interval_seconds"
-      "sync.auto_start" ]
-    |> Stdlib.List.map Cli.Completion.simple
 
+  match args with
+  | [] ->
+    ["get"; "set"; "list"] |> Stdlib.List.map Cli.Completion.simple
+  | ["get"] | ["set"] ->
+    configKeys |> Stdlib.List.map Cli.Completion.simple
   | _ -> []
 
 

packages/darklang/cli/core.dark

@@ -364,12 +364,46 @@ module Registry =
       // Completing command arguments
       let handler = findCommand parsed.commandName
       let completeFunc = handler.complete
-      completeFunc state parsed.args
+
+      // Split args into completed args and partial (last arg)
+      // parseInput appends "" for trailing space, so this always works:
+      //   "branch switch " → args=["switch",""], completedArgs=["switch"], partial=""
+      //   "branch sw"      → args=["sw"],        completedArgs=[],         partial="sw"
+      //   "branch "        → args=[],             completedArgs=[],         partial=""
+      let (completedArgs, partial) =
+        match Stdlib.List.last parsed.args with
+        | Some lastArg -> (Stdlib.List.dropLast parsed.args, lastArg)
+        | None -> ([], "")
+
+      // Get all completions for the current position
+      let completions = completeFunc state completedArgs
+
+      if Stdlib.String.isEmpty partial then
+        completions
+      else
+        // Filter by what the user has typed so far
+        let filtered =
+          completions
+          |> Stdlib.List.filter (fun item ->
+            Stdlib.String.startsWith item.value partial)
+
+        // If centralized filtering found nothing, try direct call as fallback
+        // (supports commands with smart matching like path traversal)
+        match filtered with
+        | _ :: _ -> filtered
+        | [] -> completeFunc state parsed.args
 
   let getCompletionHint (state: AppState) (input: String) : String =
-    let parsed = Completion.parseInput input
     let completions = getCompletions state input
-    let partial = Completion.getPartialCompletion parsed
+    let parsed = Completion.parseInput input
+
+    let partial =
+      if parsed.isCompletingCommand then
+        parsed.commandName
+      else
+        match Stdlib.List.last parsed.args with
+        | Some lastArg -> lastArg
+        | None -> ""
 
     let completionValues = completions |> Stdlib.List.map (fun item -> item.value)
     Completion.getHintFromCompletions partial completionValues

packages/darklang/cli/packages/db.dark

@@ -422,41 +422,14 @@ let getDBNamesForCompletion (state: Cli.AppState) : List<String> =
       name)
 
 
-let completeDBName
-  (state: Cli.AppState)
-  (partial: String)
-  : List<Cli.Completion.CompletionItem> =
-  (getDBNamesForCompletion state)
-  |> Stdlib.List.filter (fun name -> Stdlib.String.startsWith name partial)
-  |> Stdlib.List.map Cli.Completion.simple
-
-
 let complete
   (state: Cli.AppState)
   (args: List<String>)
   : List<Cli.Completion.CompletionItem> =
-  let subcommands = [ "list"; "view"; "get"; "set"; "delete"; "drop"; "query"; "help" ]
-
   match args with
   | [] ->
-    subcommands |> Stdlib.List.map Cli.Completion.simple
-
-  | [ partial ] ->
-    subcommands
-    |> Stdlib.List.filter (fun cmd -> Stdlib.String.startsWith cmd partial)
+    [ "list"; "view"; "get"; "set"; "delete"; "drop"; "query"; "help" ]
     |> Stdlib.List.map Cli.Completion.simple
-
-  | [ "view" ] -> completeDBName state ""
-  | [ "view"; partial ] -> completeDBName state partial
-  | [ "get" ] -> completeDBName state ""
-  | [ "get"; partial ] -> completeDBName state partial
-  | [ "set" ] -> completeDBName state ""
-  | [ "set"; partial ] -> completeDBName state partial
-  | [ "delete" ] -> completeDBName state ""
-  | [ "delete"; partial ] -> completeDBName state partial
-  | [ "drop" ] -> completeDBName state ""
-  | [ "drop"; partial ] -> completeDBName state partial
-  | [ "query" ] -> completeDBName state ""
-  | [ "query"; partial ] -> completeDBName state partial
-
+  | [ "view" ] | [ "get" ] | [ "set" ] | [ "delete" ] | [ "drop" ] | [ "query" ] ->
+    (getDBNamesForCompletion state) |> Stdlib.List.map Cli.Completion.simple
   | _ -> []

packages/darklang/cli/packages/undo.dark

@@ -246,8 +246,4 @@ let help (state: Cli.AppState) : Cli.AppState =
 let complete (_state: Cli.AppState) (args: List<String>) : List<Cli.Completion.CompletionItem> =
   match args with
   | [] -> ["fn"; "type"; "value"] |> Stdlib.List.map Cli.Completion.simple
-  | [partial] ->
-    ["fn"; "type"; "value"]
-    |> Stdlib.List.filter (fun item -> Stdlib.String.startsWith item partial)
-    |> Stdlib.List.map Cli.Completion.simple
   | _ -> []

packages/darklang/cli/scm/branch.dark

@@ -199,11 +199,10 @@ let execute (state: AppState) (args: List<String>) : AppState =
 
 let complete (_state: AppState) (args: List<String>) : List<Completion.CompletionItem> =
   match args with
-  | [] -> [ "list"; "create"; "switch"; "rename"; "delete" ] |> Stdlib.List.map Completion.simple
-  | [ "switch"; _ ] ->
-    let branches = SCM.Branch.list ()
-    Stdlib.List.map branches (fun b -> Completion.simple b.name)
-  | [ "delete"; _ ] ->
+  | [] ->
+    [ "list"; "create"; "switch"; "rename"; "delete" ]
+    |> Stdlib.List.map Completion.simple
+  | [ "switch" ] | [ "delete" ] ->
     let branches = SCM.Branch.list ()
     Stdlib.List.map branches (fun b -> Completion.simple b.name)
   | _ -> []

packages/darklang/cli/scripts.dark

@@ -136,41 +136,20 @@ let execute (state: AppState) (args: List<String>) : AppState =
 
 let complete (_state: AppState) (args: List<String>) : List<Completion.CompletionItem> =
   match args with
-  // if hitting `tab` right after typing `scripts`, recommend subcommands
+  // Recommend subcommands
   | [] ->
     ["list"; "view"; "add"; "edit"; "delete"; "run"]
     |> Stdlib.List.map Completion.simple
-
-  // no completions here
-  | ["list"] | ["add"] -> []
-
-  // we're referencing some specific script - recommend names
+  // Referencing a specific script - recommend names
   | ["view"] | ["edit"] | ["delete"] | ["run"] ->
-    // Complete script names
     let scripts = Builtin.pmScriptsList ()
     scripts
     |> Stdlib.List.map (fun s -> s.name)
     |> Stdlib.List.map Completion.simple
-
-  | [subcommand] ->
-    // Partial subcommand completion
-    ["list"; "view"; "add"; "edit"; "delete"; "run"]
-    |> Stdlib.List.filter (fun cmd -> Stdlib.String.startsWith cmd subcommand)
-    |> Stdlib.List.map Completion.simple
-
-  | ["view"; _] | ["delete"; _] | ["run"; _] ->
-    // CLEANUP why are we ignoring them?
-    // We should be recommending based on the names available
-    []
-
-  | ["edit"; _scriptName] ->
-    // For edit with script name, could show current content hint but keep simple
-    []
-
-  | "add" :: _ | "edit" :: _ :: _ ->
-    // For add or edit with content, no completion needed
-    []
-
+  // No completions for these
+  | ["list"] | ["add"] -> []
+  // For add or edit with content, no completion needed
+  | "add" :: _ | "edit" :: _ :: _ -> []
   | _ -> []
 
 

packages/darklang/cli/utils/completion.dark

@@ -28,6 +28,7 @@ type ParsedInput =
 
 let parseInput (input: String) : ParsedInput =
   let trimmed = Stdlib.String.trim input
+  let endsWithSpace = Stdlib.String.endsWith input " "
 
   if Stdlib.String.isEmpty trimmed then
     ParsedInput { commandName = ""; args = []; isCompletingCommand = true }
@@ -38,8 +39,16 @@ let parseInput (input: String) : ParsedInput =
 
     match words with
     | [] -> ParsedInput { commandName = ""; args = []; isCompletingCommand = true }
-    | [command] -> ParsedInput { commandName = command; args = []; isCompletingCommand = true }
-    | command :: args -> ParsedInput { commandName = command; args = args; isCompletingCommand = false }
+    | [command] ->
+      if endsWithSpace then
+        ParsedInput { commandName = command; args = []; isCompletingCommand = false }
+      else
+        ParsedInput { commandName = command; args = []; isCompletingCommand = true }
+    | command :: rest ->
+      if endsWithSpace then
+        ParsedInput { commandName = command; args = Stdlib.List.append rest [""]; isCompletingCommand = false }
+      else
+        ParsedInput { commandName = command; args = rest; isCompletingCommand = false }
 
 
 let getPartialCompletion (parsed: ParsedInput) : String =