reftest: Add the unset builtin

Author: kit-ty-kate

master_changes.md

@@ -149,6 +149,7 @@ users)
   * Bump `OPAM_REPO_SHA` in the github action workflows to allow patch 3.0.0 [#6663 @kit-ty-kate]
   * Allow `sed-cmd` to parse even if no space is after the command [#6675 @rjbou]
   * Harden the regexp used for substituting variable checksums [#6710 @kit-ty-kate]
+  * Add the `unset` builtin [#6708 @kit-ty-kate]
 
 ## Github Actions
   * bump `actions/checkout` from 4 to 5 [#6643 @kit-ty-kate]

tests/reftests/reftests.test

@@ -944,3 +944,13 @@ name: "baz"
 version: "1"
 extra-files: ["xf-baz" "md5=9ac116bceba2bdf45065df19d26a6b64"]
 ### opam-cache repo inexistent
+### :V:4: unset
+### env | grep REFTEST_UNSET
+### REFTEST_UNSET=test
+### env | grep REFTEST_UNSET
+REFTEST_UNSET=test
+### REFTEST_UNSET=""
+### env | grep REFTEST_UNSET
+REFTEST_UNSET=
+### unset REFTEST_UNSET
+### env | grep REFTEST_UNSET

tests/reftests/run.ml

@@ -285,6 +285,7 @@ type command =
              unordered: bool;
              sort: bool;}
   | Export of (string * [`eq | `pluseq | `eqplus] * string) list
+  | Unset of string list
   | Comment of string
 
 module Parse = struct
@@ -496,6 +497,8 @@ module Parse = struct
         Opamfile { files = args; filter = rewr; }
       | Some "json-cat" ->
         Json { files = args; filter = rewr; }
+      | Some "unset" ->
+        Unset args
       | Some "opam-cache" ->
         let kind, switch, nvs =
           match args with
@@ -984,6 +987,8 @@ let run_test ?(vars=[]) ~opam t =
                in
                (v, value) :: List.filter (fun (w, _) -> not (String.equal v w)) vars)
             vars bindings
+        | Unset l ->
+          List.filter (fun (w, _) -> not (List.exists (fun v -> String.equal v w) l)) vars
         | Opamfile { files; filter } ->
           let files =
             List.map (fun s ->