-explainEmbed

4 files changed, 20 insertions, 1 deletions

diff --git a/doc/manual.tex b/doc/manual.tex
index 457df39b..144c2017 100644
--- a/doc/manual.tex
+++ b/doc/manual.tex
@@ -266,6 +266,8 @@ sqlite3 path/to/database/file <app.sql
 
 \item \texttt{-dumpSource}: When compilation fails, output to stderr the complete source code of the last intermediate program before the compilation phase that signaled the error.  (Warning: these outputs can be very long and aren't especially optimized for readability!)
 
+\item \texttt{-explainEmbed}: Trigger more verbose error messages about inability to embed server-side values in client-side code.
+
 \item \texttt{-limit class num}: Equivalent to the \texttt{limit} directive from \texttt{.urp} files
 
 \item \texttt{-moduleOf FILENAME}: Prints the Ur/Web module name corresponding to source file \texttt{FILENAME}, exiting immediately afterward.
diff --git a/src/jscomp.sig b/src/jscomp.sig
index 929c507d..5b8723b4 100644
--- a/src/jscomp.sig
+++ b/src/jscomp.sig
@@ -29,4 +29,8 @@ signature JSCOMP = sig
 
     val process : Mono.file -> Mono.file
 
+    val explainEmbed : bool ref
+    (* Output verbose error messages about inability to embed server-side
+     * values in client-side code? *)
+
 end
diff --git a/src/jscomp.sml b/src/jscomp.sml
index 4a2c0365..bcabed0b 100644
--- a/src/jscomp.sml
+++ b/src/jscomp.sml
@@ -41,6 +41,8 @@ structure TM = BinaryMapFn(struct
                            val compare = U.Typ.compare
                            end)
 
+val explainEmbed = ref false
+
 type state = {
      decls : (string * int * (string * int * typ option) list) list,
      script : string list,
@@ -267,7 +269,12 @@ fun process (file : file) =
                          ((EApp ((ENamed n', loc), e), loc), st)
                      end)
 
-              | _ => ((*Print.prefaces "Can't embed" [("t", MonoPrint.p_typ MonoEnv.empty t)];*)
+              | _ => (if !explainEmbed then
+                          Print.prefaces "Can't embed" [("loc", Print.PD.string (ErrorMsg.spanToString loc)),
+                                                        ("e", MonoPrint.p_exp MonoEnv.empty e),
+                                                        ("t", MonoPrint.p_typ MonoEnv.empty t)]
+                      else
+                          ();
                       raise CantEmbed t)
 
         fun unurlifyExp loc (t : typ, st) =
@@ -400,6 +407,9 @@ fun process (file : file) =
 
                 fun jsE inner (e as (_, loc), st) =
                     let
+                        (*val () = Print.prefaces "jsExp" [("e", MonoPrint.p_exp MonoEnv.empty e),
+                                                         ("loc", Print.PD.string (ErrorMsg.spanToString loc))]*)
+
                         val str = str loc
 
                         fun patCon pc =
diff --git a/src/main.mlton.sml b/src/main.mlton.sml
index 71fefc48..bfc18e59 100644
--- a/src/main.mlton.sml
+++ b/src/main.mlton.sml
@@ -174,6 +174,9 @@ fun oneRun args =
                      else
                          Settings.addLimit (class, n);
                  doArgs rest)
+              | "-explainEmbed" :: rest =>
+                (JsComp.explainEmbed := true;
+                 doArgs rest)
               | arg :: rest =>
                 (if size arg > 0 andalso String.sub (arg, 0) = #"-" then
                      raise Fail ("Unknown flag " ^ arg)