Rewrite the conflict explanation extraction mechanism

src/client/opamClient.ml

@@ -273,12 +273,13 @@ let upgrade_t
   | requested, Conflicts cs ->
     log "conflict!";
     if not (OpamPackage.Name.Set.is_empty requested) then
-      (OpamConsole.msg "%s"
-         (OpamCudf.string_of_conflict t.packages
+      (OpamConsole.error "Package conflict!";
+       OpamConsole.errmsg "%s"
+         (OpamCudf.string_of_conflicts t.packages
             (OpamSwitchState.unavailable_reason t) cs);
        OpamStd.Sys.exit_because `No_solution);
-    let reasons, chains, cycles =
-      OpamCudf.strings_of_conflict t.packages
+    let reasons, cycles =
+      OpamCudf.conflict_explanations t.packages
         (OpamSwitchState.unavailable_reason t) cs in
     if cycles <> [] then begin
       OpamConsole.error
@@ -292,11 +293,8 @@ let upgrade_t
       OpamConsole.warning
         "Upgrade is not possible because of conflicts or packages that \
          are no longer available:";
-      OpamConsole.errmsg "%s" (OpamStd.Format.itemize (fun x -> x) reasons);
-      if chains <> [] then
-        OpamConsole.errmsg
-          "The following dependencies are the cause:\n%s"
-          (OpamStd.Format.itemize (fun x -> x) chains);
+      OpamConsole.errmsg "%s"
+        (OpamStd.Format.itemize (OpamCudf.string_of_conflict ~indent:4) reasons);
       OpamConsole.errmsg
         "\nYou may run \"opam upgrade --fixup\" to let opam fix the \
          current state.\n"
@@ -476,7 +474,7 @@ let fixup t =
     | _, Success _ -> true
     | _, Conflicts cs ->
       log "conflict: %a"
-        (slog (OpamCudf.string_of_conflict t.packages @@
+        (slog (OpamCudf.string_of_conflicts t.packages @@
                OpamSwitchState.unavailable_reason t))
         cs;
       false
@@ -513,7 +511,7 @@ let fixup t =
          available. Either fix their prerequisites or change them through \
          'opam list --base' and 'opam switch set-base'.";
       OpamConsole.errmsg "%s"
-        (OpamCudf.string_of_conflict t.packages
+        (OpamCudf.string_of_conflicts t.packages
            (OpamSwitchState.unavailable_reason t) cs);
       t, Conflicts cs
     | Success solution ->
@@ -1217,8 +1215,9 @@ let install_t t ?ask ?(ignore_conflicts=false) ?(depext_only=false)
   let t, solution = match solution with
     | Conflicts cs ->
       log "conflict!";
-      OpamConsole.msg "%s"
-        (OpamCudf.string_of_conflict t.packages
+      OpamConsole.error "Package conflict!";
+      OpamConsole.errmsg "%s"
+        (OpamCudf.string_of_conflicts t.packages
            (OpamSwitchState.unavailable_reason t) cs);
       t, if depext_only then None else Some (Conflicts cs)
     | Success solution ->

src/client/opamListCommand.ml

@@ -271,7 +271,7 @@ let apply_selector ~base st = function
         "No solution%s for %s: %s"
         (if tog.depopts then " including optional dependencies" else "")
         (OpamFormula.string_of_atoms atoms)
-        (OpamCudf.string_of_conflict st.packages
+        (OpamCudf.string_of_conflicts st.packages
            (OpamSwitchState.unavailable_reason st) cs))
   | Pattern (psel, pat) ->
     let re =

src/client/opamSolution.ml

@@ -238,22 +238,15 @@ module Json = struct
       in
       OpamJson.append "solution" (`A (List.rev to_proceed))
     | Conflicts cs ->
-      let causes,_,cycles =
-        OpamCudf.strings_of_conflict
+      let causes, cycles =
+        OpamCudf.conflict_explanations
           t.packages (OpamSwitchState.unavailable_reason t) cs
       in
-      let chains = OpamCudf.conflict_chains t.packages cs in
-      let jchains =
-        `A (List.map (fun c ->
-            `A ((List.map (fun f ->
-                `String (OpamFormula.to_string (Atom f))) c)))
-            chains)
-      in
+      let causes = List.map OpamCudf.string_of_conflict causes in
       let toj l = `A (List.map (fun s -> `String s) l) in
       OpamJson.append "conflicts"
         (`O ((if cycles <> [] then ["cycles", toj cycles] else []) @
-             (if causes <> [] then ["causes", toj causes] else []) @
-             (if chains <> [] then ["broken-deps", jchains] else [])))
+             (if causes <> [] then ["causes", toj causes] else [])))
 
   let exc e =
     let lmap f l = List.rev (List.rev_map f l) in
@@ -1196,7 +1189,7 @@ let resolve_and_apply ?ask t action ~orphans ?reinstall ~requested ?add_roots
   | Conflicts cs ->
     log "conflict!";
     OpamConsole.msg "%s"
-      (OpamCudf.string_of_conflict t.packages
+      (OpamCudf.string_of_conflicts t.packages
          (OpamSwitchState.unavailable_reason t) cs);
     t, Conflicts cs
   | Success solution ->

src/client/opamSwitchCommand.ml

@@ -223,10 +223,12 @@ let install_compiler ?(additional_installs=[]) ?(deps_only=false) t =
   let solution = match solution with
     | Success s -> s
     | Conflicts cs ->
-      OpamConsole.error_and_exit `No_solution
-        "Could not resolve base install for this switch:\n%s"
-        (OpamCudf.string_of_conflict t.packages
+      OpamConsole.error
+        "Could not resolve base install for this switch:";
+      OpamConsole.errmsg "%s\n"
+        (OpamCudf.string_of_conflicts t.packages
            (OpamSwitchState.unavailable_reason t) cs);
+      OpamStd.Sys.exit_because `No_solution
   in
   let () = match OpamSolver.stats solution with
     | { s_install = _; s_reinstall = 0; s_upgrade = 0;

src/format/opamFormula.mli

@@ -165,6 +165,11 @@ val satisfies_depends: OpamPackage.Set.t -> t -> bool
     all disjunction cases) *)
 val packages: OpamPackage.Set.t -> t -> OpamPackage.Set.t
 
+val compare_nc:
+  (OpamPackage.Name.t * version_formula) ->
+  (OpamPackage.Name.t * version_formula) ->
+  int
+
 (** Convert a formula to CNF *)
 val cnf_of_formula: 'a formula -> 'a formula