From bb5cd9074a70c5bc8713e90362dd84676f91d5d6 Mon Sep 17 00:00:00 2001
From: Niko Huurre <nhuurre@protonmail.com>
Date: Tue, 23 Mar 2021 14:57:19 +0200
Subject: [PATCH] handle file not found error

---
 src/frontend/Parse.ml                       | 23 +++++++++++++--------
 src/middle/Errors.ml                        |  6 +++++-
 src/middle/Errors.mli                       |  5 ++++-
 test/integration/cli-args/dune              | 11 ++++++++++
 test/integration/cli-args/notfound.expected |  2 ++
 5 files changed, 36 insertions(+), 11 deletions(-)
 create mode 100644 test/integration/cli-args/notfound.expected

diff --git a/src/frontend/Parse.ml b/src/frontend/Parse.ml
index c1bcc2fa9e..6a9c06f401 100644
--- a/src/frontend/Parse.ml
+++ b/src/frontend/Parse.ml
@@ -71,13 +71,18 @@ let parse_string parse_fun str =
   parse parse_fun lexbuf
 
 let parse_file parse_fun path =
-  let chan = In_channel.create path in
-  let lexbuf =
-    let open Lexing in
-    let lexbuf = from_channel chan in
-    lexbuf.lex_start_p
-    <- {pos_fname= path; pos_lnum= 1; pos_bol= 0; pos_cnum= 0} ;
-    lexbuf.lex_curr_p <- lexbuf.lex_start_p ;
-    lexbuf
+  let chan =
+    try Ok (In_channel.create path) with _ -> Error (Errors.FileNotFound path)
   in
-  parse parse_fun lexbuf
+  match chan with
+  | Error err -> (Error err, [])
+  | Ok chan ->
+      let lexbuf =
+        let open Lexing in
+        let lexbuf = from_channel chan in
+        lexbuf.lex_start_p
+        <- {pos_fname= path; pos_lnum= 1; pos_bol= 0; pos_cnum= 0} ;
+        lexbuf.lex_curr_p <- lexbuf.lex_start_p ;
+        lexbuf
+      in
+      parse parse_fun lexbuf
diff --git a/src/middle/Errors.ml b/src/middle/Errors.ml
index 9b26186c49..e90e04f17c 100644
--- a/src/middle/Errors.ml
+++ b/src/middle/Errors.ml
@@ -20,7 +20,10 @@ exception SemanticError of Semantic_error.t
     [msg]. *)
 exception FatalError of string
 
-type t = Syntax_error of syntax_error | Semantic_error of Semantic_error.t
+type t =
+  | FileNotFound of string
+  | Syntax_error of syntax_error
+  | Semantic_error of Semantic_error.t
 
 (* A fatal error reported by the toplevel *)
 let fatal_error ?(msg = "") _ =
@@ -57,6 +60,7 @@ let pp_syntax_error ?printed_filename ppf = function
         pp_context_with_message (message, loc)
 
 let pp ?printed_filename ppf = function
+  | FileNotFound f -> Fmt.pf ppf "Cannot not open file %s@." f
   | Syntax_error e -> pp_syntax_error ?printed_filename ppf e
   | Semantic_error e -> pp_semantic_error ?printed_filename ppf e
 
diff --git a/src/middle/Errors.mli b/src/middle/Errors.mli
index d5437cfbab..8b3cc78d91 100644
--- a/src/middle/Errors.mli
+++ b/src/middle/Errors.mli
@@ -13,7 +13,10 @@ exception SyntaxError of syntax_error
     [msg], occurring at location [loc]. *)
 exception SemanticError of Semantic_error.t
 
-type t = Syntax_error of syntax_error | Semantic_error of Semantic_error.t
+type t =
+  | FileNotFound of string
+  | Syntax_error of syntax_error
+  | Semantic_error of Semantic_error.t
 
 val pp : ?printed_filename:string -> t Fmt.t
 val to_string : t -> string
diff --git a/test/integration/cli-args/dune b/test/integration/cli-args/dune
index 7b505903e8..c212415a31 100644
--- a/test/integration/cli-args/dune
+++ b/test/integration/cli-args/dune
@@ -30,3 +30,14 @@
 (alias
  (name runtest)
  (action (diff info.expected info.output)))
+
+(rule
+ (targets notfound.output)
+ (deps (package stanc))
+ (action
+  (with-stdout-to %{targets}
+   (run %{bin:run_bin_on_args} "%{bin:stanc}" notfound.stan))))
+
+(alias
+ (name runtest)
+ (action (diff notfound.expected notfound.output)))
\ No newline at end of file
diff --git a/test/integration/cli-args/notfound.expected b/test/integration/cli-args/notfound.expected
new file mode 100644
index 0000000000..9163338935
--- /dev/null
+++ b/test/integration/cli-args/notfound.expected
@@ -0,0 +1,2 @@
+  $ ../../../../install/default/bin/stanc notfound.stan
+Cannot not open file notfound.stan