test(frontend): Add scope `open` test

Pantograph/Frontend/Basic.lean

@@ -40,6 +40,7 @@ def stxByteRange (stx : Syntax) : String.Pos × String.Pos :=
 abbrev FrontendM := Elab.Frontend.FrontendM
 
 structure CompilationStep where
+  scope : Elab.Command.Scope
   fileName : String
   fileMap : FileMap
   src : Substring
@@ -74,7 +75,7 @@ def processOneCommand: FrontendM (CompilationStep × Bool) := do
   let msgs := s'.messages.toList.drop s.messages.toList.length
   let trees := s'.infoState.trees.drop s.infoState.trees.size
   let ⟨_, fileName, fileMap⟩  := (← read).inputCtx
-  return ({ fileName, fileMap, src, stx, before, after, msgs, trees }, done)
+  return ({ scope := s.scopes.head!, fileName, fileMap, src, stx, before, after, msgs, trees }, done)
 
 partial def mapCompilationSteps { α } (f: CompilationStep → IO α) : FrontendM (List α) := do
   let (cmd, done) ← processOneCommand

Test/Frontend.lean

@@ -1,11 +1,27 @@
-import LSpec
 import Pantograph
 import Repl
 import Test.Common
 
+import LSpec
+
 open Lean Pantograph
 namespace Pantograph.Test.Frontend
 
+def runFrontend { α } (source: String) (f : Frontend.CompilationStep → IO α) : MetaM (List α) := do
+  let filename := "<anonymous>"
+  let (context, state) ← do Frontend.createContextStateFromFile source filename (← getEnv) {}
+  let m := Frontend.mapCompilationSteps f
+  m.run context |>.run' state
+
+def test_open : TestT MetaM Unit := do
+  let sketch := "
+open Nat
+example : ∀ (n m: Nat), n + m = m + n := by
+  apply add_comm
+  "
+  let errors ← runFrontend sketch λ step => step.msgs.mapM (·.toString)
+  checkEq "errors" errors [[]]
+
 def collectSorrysFromSource (source: String) (options : Frontend.GoalCollectionOptions := {})
     : MetaM (List GoalState) := do
   let filename := "<anonymous>"
@@ -233,6 +249,7 @@ theorem mystery [SizeOf α] (as : List α) (i : Fin as.length) : sizeOf (as.get
 
 def suite (env : Environment): List (String × IO LSpec.TestSeq) :=
   let tests := [
+    ("open", test_open),
     ("multiple_sorrys_in_proof", test_multiple_sorrys_in_proof),
     ("sorry_in_middle", test_sorry_in_middle),
     ("sorry_in_induction", test_sorry_in_induction),