Add support for erasing in multiple scopes.

Allow erasing in multiple scopes in one go. Closes #7711.

CHANGELOG.rst

@@ -25,6 +25,9 @@ Notable improvements and fixes
     for a,b in y 1 z 3
         ^~^
 - A new helper function ``fish_delta`` can be used to show the difference to fish's stock configuration (:issue:`9255`).
+- It is now possible to specify multiple scopes for ``set -e`` and all of the named variables present in any of the specified scopes will be erased. This makes it possible to remove all instances of a variable in all scopes (``set -efglU foo``) in one go (:issue:`7711`).
+
+=======
 
 Deprecations and removed features
 ---------------------------------

doc_src/cmds/set.rst

@@ -68,7 +68,7 @@ The following other options are available:
     Causes the values to be prepended to the current set of values for the variable. This can be used with **--append** to both append and prepend at the same time. This cannot be used when assigning to a variable slice.
 
 **-e** or **--erase**
-    Causes the specified shell variables to be erased
+    Causes the specified shell variables to be erased. Supports erasing from multiple scopes at once.
 
 **-q** or **--query**
     Test if the specified variable names are defined. Does not output anything, but the builtins exit status is the number of variables specified that were not defined, up to a maximum of 255. If no variable was given, it also returns 255.

src/builtins/set.cpp

@@ -204,12 +204,15 @@ static int validate_cmd_opts(const wchar_t *cmd, const set_cmd_opts_t &opts, int
         return STATUS_INVALID_ARGS;
     }
 
-    // Variables can only have one scope.
+    // Variables can only have one scope...
     if (opts.local + opts.function + opts.global + opts.universal > 1) {
+        // ..unless we are erasing a variable, in which case we can erase from several in one go.
+        if (!opts.erase) {
             streams.err.append_format(BUILTIN_ERR_GLOCAL, cmd);
             builtin_print_error_trailer(parser, streams.err, cmd);
             return STATUS_INVALID_ARGS;
         }
+    }
 
     // Variables can only have one export status.
     if (opts.exportv && opts.unexport) {
@@ -391,7 +394,7 @@ static maybe_t<split_var_t> split_var_and_indexes(const wchar_t *arg, env_mode_f
     return res;
 }
 
-/// Given a list of values and 1-based indexes, return a new list, with those elements removed.
+/// Given a list of values and 1-based indexes, return a new list with those elements removed.
 /// Note this deliberately accepts both args by value, as it modifies them both.
 static wcstring_list_t erased_at_indexes(wcstring_list_t input, std::vector<long> indexes) {
     // Sort our indexes into *descending* order.
@@ -620,7 +623,11 @@ static int builtin_set_show(const wchar_t *cmd, const set_cmd_opts_t &opts, int
 static int builtin_set_erase(const wchar_t *cmd, set_cmd_opts_t &opts, int argc,
                              const wchar_t **argv, parser_t &parser, io_streams_t &streams) {
     int ret = STATUS_CMD_OK;
-    env_mode_flags_t scope = compute_scope(opts);
+    env_mode_flags_t scopes = compute_scope(opts);
+    // `set -e` is allowed to be called with multiple scopes.
+    for (int bit = 0; 1<<bit <= ENV_USER; ++bit) {
+        int scope = scopes & 1<<bit;
+        if (scope == 0 || (scope == ENV_USER && scopes != ENV_USER)) continue;
         for (int i = 0; i < argc; i++) {
             auto split = split_var_and_indexes(argv[i], scope, parser.vars(), streams);
             if (!split) {
@@ -661,6 +668,7 @@ static int builtin_set_erase(const wchar_t *cmd, set_cmd_opts_t &opts, int argc,
                 warn_if_uvar_shadows_global(cmd, opts, split->varname, streams, parser);
             }
         }
+    }
     return ret;
 }
 

tests/checks/set.fish

@@ -921,3 +921,23 @@ foo=bar $FISH -c 'set foo 1 2 3; set --show foo'
 # CHECK: $foo[2]: |2|
 # CHECK: $foo[3]: |3|
 # CHECK: $foo: originally inherited as |bar|
+
+# Verify behavior of erasing in multiple scopes simultaneously
+set -U marbles global
+set -g marbles global
+set -l marbles local
+
+set -eUg marbles
+set -ql marbles || echo "erased in more scopes than it should!"
+set -qg marbles && echo "didn't erase from global scope!"
+set -qU marbles && echo "didn't erase from universal scope!"
+
+begin
+    set -l secret local 4 8 15 16 23 42
+    set -g secret global 4 8 15 16 23 42
+    set -egl secret[3..5]
+    echo $secret
+    # CHECK: local 4 23 42
+end
+echo $secret
+# CHECK: global 4 23 42