investigate differences in build, install, and uri when opam file differed

lib/views.ml

@@ -226,7 +226,7 @@ let job_build
        | Some previous_build when successful_build ->
          p [
            a ~a:[Fmt.kstr a_href "/compare/%a/%a/opam-switch"
-                   Uuidm.pp uuid Uuidm.pp previous_build.Builder_db.Build.Meta.uuid]
+                   Uuidm.pp previous_build.Builder_db.Build.Meta.uuid Uuidm.pp uuid]
              [txt "Compare opam-switch with previous build"];
          ]
        | _ -> txt "");
@@ -281,12 +281,42 @@ let package_diffs diffs =
       ])
     diffs
 
+let opam_diffs diffs =
+  List.concat_map (fun pd ->
+        h4 [ txtf "%a" Opamdiff.pp_opam_diff pd ] ::
+        (match pd.Opamdiff.build with None -> [] | Some a ->
+          let l, r = Opamdiff.commands_to_strings a in
+          [
+            h5 [ txt "build instruction (without common prefix) modifications, old:" ] ;
+            ul (List.map (fun s -> li [ txt s ]) l) ;
+            h5 [ txt "new" ] ;
+            ul (List.map (fun s -> li [ txt s ]) r)
+          ]) @
+        (match pd.Opamdiff.install with None -> [] | Some a ->
+          let l, r = Opamdiff.commands_to_strings a in
+          [
+            h5 [ txt "install instruction (without common prefix) modifications, old:" ] ;
+            ul (List.map (fun s -> li [ txt s ]) l) ;
+            h5 [ txt "new" ] ;
+            ul (List.map (fun s -> li [ txt s ]) r)
+         ]) @
+      (match pd.Opamdiff.url with None -> [] | Some a ->
+          let l, r = Opamdiff.opt_url_to_string a in
+          [
+            h5 [ txt "URL" ] ;
+            txtf "old: %s" l;
+            br ();
+            txtf "new: %s" r
+          ]) @
+      [ br () ])
+    diffs
+
 let compare_opam job_left job_right
     (build_left : Builder_db.Build.t) (build_right : Builder_db.Build.t)
     (same, opam_diff, version_diff, left, right) =
   layout ~title:(Fmt.strf "Comparing opam switches between builds %a and %a"
                    Uuidm.pp build_left.uuid Uuidm.pp build_right.uuid)
-    [
+    ([
       h1 [txt "Comparing opam switches"];
       h2 [
         txt "Builds ";
@@ -317,7 +347,7 @@ let compare_opam job_left job_right
         ];
         li [
           a ~a:[a_href "#packages-opam-diff"]
-            [txtf "%d packages with changes in their opam file" (OpamPackage.Set.cardinal opam_diff)]
+            [txtf "%d packages with changes in their opam file" (List.length opam_diff)]
         ];
         li [
           a ~a:[a_href "#packages-unchanged"]
@@ -334,9 +364,9 @@ let compare_opam job_left job_right
         [txt "Packages with version changes"];
       code (package_diffs version_diff);
       h3 ~a:[a_id "packages-opam-diff"]
-        [txt "Packages with changes in their opam file"];
-      code (packages opam_diff);
+        [txt "Packages with changes in their opam file"]] @
+      opam_diffs opam_diff @ [
       h3 ~a:[a_id "packages-unchanged"]
         [txt "Unchanged packages"];
       code (packages same);
-    ]
+    ])

opamdiff/opamdiff.ml

@@ -23,6 +23,75 @@ let pp_version_diff ppf { name; version_left; version_right } =
     (OpamPackage.Version.to_string version_left)
     (OpamPackage.Version.to_string version_right)
 
+type opam_diff = {
+  pkg : OpamPackage.t ;
+  build : (OpamTypes.command list * OpamTypes.command list) option ;
+  install : (OpamTypes.command list * OpamTypes.command list) option ;
+  url : (OpamFile.URL.t option * OpamFile.URL.t option) option ;
+  otherwise_equal : bool ;
+}
+
+let commands_to_strings (l, r) =
+    let v a =
+      OpamPrinter.FullPos.value (OpamPp.print OpamFormat.V.command a)
+    in
+    List.map v l, List.map v r
+
+let opt_url_to_string (l, r) =
+  let url_to_s = function
+    | None -> "" | Some u -> OpamFile.URL.write_to_string u
+  in
+  url_to_s l, url_to_s r
+
+let pp_opam_diff ppf { pkg ; otherwise_equal ; _ } =
+  Format.fprintf ppf "%a%s"
+    pp_opampackage pkg
+    (if otherwise_equal then "" else " (and additional changes)")
+
+let rec strip_common_prefix a b =
+  match a, b with
+  | hd::tl, hd'::tl' ->
+    if hd = hd' then
+      strip_common_prefix tl tl'
+    else
+      a, b
+  | a, b -> a, b
+
+let detailed_opam_diff pkg l r =
+  let no_build_install_url p =
+    OpamFile.OPAM.with_url_opt None
+      (OpamFile.OPAM.with_install []
+         (OpamFile.OPAM.with_build [] p))
+  in
+  let otherwise_equal =
+    OpamFile.OPAM.effectively_equal
+      (no_build_install_url l) (no_build_install_url r)
+  and build =
+    if OpamFile.OPAM.build l = OpamFile.OPAM.build r then
+      None
+    else
+      Some (strip_common_prefix (OpamFile.OPAM.build l) (OpamFile.OPAM.build r))
+  and install =
+    if OpamFile.OPAM.install l = OpamFile.OPAM.install r then
+      None
+    else
+      Some (strip_common_prefix (OpamFile.OPAM.install l) (OpamFile.OPAM.install r))
+  and url =
+    if OpamFile.OPAM.url l = OpamFile.OPAM.url r then
+      None
+    else
+      Some (OpamFile.OPAM.url l, OpamFile.OPAM.url r)
+  in
+  { pkg ; build ; install ; url ; otherwise_equal }
+
+let detailed_opam_diffs left right pkgs =
+  OpamPackage.Set.fold (fun p acc ->
+      let find = OpamPackage.Name.Map.find p.name in
+      let opam_left = find left.OpamFile.SwitchExport.overlays
+      and opam_right = find right.OpamFile.SwitchExport.overlays in
+      (detailed_opam_diff p opam_left opam_right) :: acc)
+    pkgs []
+
 let compare left right =
   let packages_left = packages left and packages_right = packages right in
   let module Set = OpamPackage.Set in
@@ -53,7 +122,8 @@ let compare left right =
         | None ->
           None)
       (Set.elements packages_left)
-  and left = diff packages_left packages_right
-  and right = diff packages_right packages_left
+  and left_pkgs = diff packages_left packages_right
+  and right_pkgs = diff packages_right packages_left
   in
-  (same, opam_diff, version_diff, left, right)
+  let opam_diff = detailed_opam_diffs left right opam_diff in
+  (same, opam_diff, version_diff, left_pkgs, right_pkgs)