Detect cycles in imports

src/Idris/ModTree.idr

@@ -85,14 +85,17 @@ mkModTree loc done mod
                          Nothing =>
                            do (file, modInfo) <- readHeader loc mod
                               let imps = map path (imports modInfo)
-                              ms <- traverse (mkModTree loc done) imps
+                              ms <- traverse (mkModTree loc (mod :: done)) imps
                               let mt = MkModTree mod (Just file) ms
                               all <- get AllMods
                               put AllMods ((mod, mt) :: all)
                               pure mt
                          Just m => pure m)
                 -- Couldn't find source, assume it's in a package directory
-                (\err => pure (MkModTree mod Nothing []))
+                (\err => 
+                    case err of
+                         CyclicImports _ => throw err
+                         _ => pure (MkModTree mod Nothing []))
 
 -- Given a module tree, returns the modules in the reverse order they need to
 -- be built, including their dependencies
@@ -112,7 +115,6 @@ mkBuildMods acc mod
 
 -- Given a main file name, return the list of modules that need to be
 -- built for that main file, in the order they need to be built
-export
 getBuildMods : {auto c : Ref Ctxt Defs} ->
                {auto o : Ref ROpts REPLOpts} ->
                FC -> (mainFile : String) -> 

tests/Main.idr

@@ -32,7 +32,7 @@ idrisTests
        "coverage001", "coverage002", "coverage003", "coverage004",
        "error001", "error002", "error003", "error004", "error005",
        "error006", "error007", "error008", "error009", "error010",
-       "import001", "import002", "import003",
+       "import001", "import002", "import003", "import004",
        "interactive001", "interactive002", "interactive003", "interactive004",
        "interactive005", "interactive006", "interactive007", "interactive008",
        "interactive009", "interactive010", "interactive011", "interactive012",

tests/idris2/import004/Cycle1.idr

@@ -0,0 +1,3 @@
+module Cycle1
+
+import Cycle2

tests/idris2/import004/Cycle2.idr

@@ -0,0 +1,3 @@
+module Cycle2
+
+import Cycle1

tests/idris2/import004/Loop.idr

@@ -0,0 +1,3 @@
+module Loop
+
+import Loop

tests/idris2/import004/expected

@@ -0,0 +1,2 @@
+Uncaught error: Module imports form a cycle: Cycle2 -> Cycle1 -> Cycle1
+Uncaught error: Module imports form a cycle: Loop -> Loop

tests/idris2/import004/run

@@ -0,0 +1,4 @@
+$1 Cycle1.idr
+$1 Loop.idr
+
+rm -rf build