feat(exec): support absolute paths

We add support for absolute paths passed to dune exec. There is quite
some cleanup that needs to be done in the path handling in dune exec,
but for now we have kept this change small and tried to record some of
its behaviour.

A current limitation is that if a watch mode dune is running then dune
exec will connect via RPC and will not be able to correctly deal with an
absolute path.

Signed-off-by: Ali Caglayan <[email protected]>

Author: Alizter

bin/exec.ml

@@ -136,18 +136,19 @@ let get_path common sctx ~prog =
      | true -> Memo.return path
      | false -> not_found_with_suggestions ~dir ~prog)
   | Absolute ->
-    (match
-       let prog = Path.of_string prog in
-       if Path.exists prog
-       then Some prog
-       else if not Sys.win32
-       then None
-       else (
-         let prog = Path.extend_basename prog ~suffix:Bin.exe in
-         Option.some_if (Path.exists prog) prog)
-     with
-     | Some prog -> Memo.return prog
-     | None -> not_found_with_suggestions ~dir ~prog)
+    let path =
+      Path.of_string prog
+      |> Path.Expert.try_localize_external
+      |> Path.to_string
+      |> Path.relative_to_source_in_build_or_external ~dir
+    in
+    if Path.equal (Path.external_ Path.External.root) path
+    then not_found ~hints:[] ~prog
+    else
+      Build_system.file_exists path
+      >>= (function
+       | true -> Memo.return path
+       | false -> not_found_with_suggestions ~dir ~prog)
 ;;
 
 let get_path_and_build_if_necessary common sctx ~no_rebuild ~prog =

doc/changes/12094.md

@@ -0,0 +1,2 @@
+- `dune exec` now accepts absolute paths inside the workspace. (#12094,
+  @Alizter)

test/blackbox-tests/test-cases/exec/exec-abs.t

@@ -16,9 +16,23 @@ Testing interaction of dune exec and absolute directories.
   $ dune exec ./foo.exe
   hi
 
+Dune exec is able to handle absolute executable paths.
+
   $ dune exec $PWD/foo.exe
-  Error: Program
-  '$TESTCASE_ROOT/foo.exe'
-  not found!
+  hi
+
+Lets check some validation:
+
+  $ dune exec ..
+  Error: Program '..' not found!
+  [1]
+  $ dune exec .
+  Error: Program '.' not found!
+  [1]
+  $ dune exec /.
+  Error: Program '/.' not found!
+  [1]
+  $ dune exec /
+  Error: Program '/' not found!
   [1]