reftest: lint add W69 that checks that there is no several '+' in pac…

…kage name for variable in string, and advise the good syntax.

src/state/opamFileTools.ml

@@ -875,6 +875,31 @@ let t_lint ?check_extra_files ?(check_upstream=false) ?(all=false) t =
     cond 68 `Warning
       "Missing field 'license'"
       (t.license = []);
+    (let vars =
+       List.flatten @@
+       List.map (fun s ->
+           List.filter_map
+             (fun f ->
+                try
+                  let _ =
+                    OpamTypesBase.filter_ident_of_string_interp
+                      ~accept:false f
+                  in
+                  None
+                with OpamTypesBase.Parse_error (p,v) ->
+                  Some (p,v)
+             )
+             (OpamFilter.extract_variables_from_string s))
+         all_expanded_strings
+     in
+     cond 69 `Warning
+       "Package name in variable in string interpolation contains several \
+        '+', use"
+       ~detail:(List.map (fun (p,v) ->
+           Printf.sprintf "'?%s:%s:' instead of '%s:%s'"
+             p v p v)
+           vars)
+       (vars <> []));
   ]
   in
   format_errors @

tests/reftests/lint.test

@@ -942,3 +942,23 @@ bug-reports: "https://nobug"
 ### opam lint ./lint.opam
 ${BASEDIR}/lint.opam: Warnings.
            warning 68: Missing field 'license'
+### : W69: Package name in variable in string interpolation contains several '+'
+### <lint.opam>
+opam-version: "2.0"
+name: "conf-g++"
+synopsis: "A word"
+description: "Two words."
+authors: "the testing team"
+homepage: "egapemoh"
+maintainer: "maint@tain.er"
+license: "ISC"
+dev-repo: "hg+https://to@li.nt"
+bug-reports: "https://nobug"
+messages: [
+  "foo" { "%{?conf-c++:installed:}%" }
+  "bar" { "%{conf-g++:installed}%" }
+  "baz" { "%{abc+xyz+jkl:installed}%" }
+]
+### opam lint ./lint.opam
+${BASEDIR}/lint.opam: Warnings.
+           warning 69: Package name in variable in string interpolation contains several '+', use: "'?conf-g++:installed:' instead of 'conf-g++:installed'"