Point to builtins begin/end when a failed command starts with "{"

Closes #6415

CHANGELOG.rst

@@ -55,6 +55,7 @@ Interactive improvements
 - The Web-based configuration and documentation now feature a dark mode if the browser requests it (:issue:`8043`).
 - Color variables can now also be given like ``--background red`` and ``-b red``, not just ``--background=red`` (:issue:`8053`).
 - ``exit`` run within ``fish_prompt`` now exits properly (:issue:`8033`).
+- When attempting to execute the unsupported POSIX-style brace command group (``{ ... }``) fish will suggest its equivalent ``begin; ...; end`` commands (:issue:`6415`).
 
 New or improved bindings
 ^^^^^^^^^^^^^^^^^^^^^^^^

src/parse_constants.h

@@ -279,4 +279,8 @@ enum class pipeline_position_t {
 #define ERROR_TIME_BACKGROUND \
     _(L"'time' is not supported for background jobs. Consider using 'command time'.")
 
+/// Error issued on { echo; echo }.
+#define ERROR_NO_BRACE_GROUPING \
+    _(L"'{ ... }' is not supported for grouping commands. Please use 'begin; ...; end'")
+
 #endif

src/parse_execution.cpp

@@ -779,6 +779,10 @@ end_execution_reason_t parse_execution_context_t::handle_command_not_found(
         }
     }
 
+    if (!cmd_str.empty() && cmd_str.at(0) == L'{') {
+        error.append(ERROR_NO_BRACE_GROUPING);
+    }
+
     // Here we want to report an error (so it shows a backtrace).
     // If the handler printed text, that's already shown, so error will be empty.
     return this->report_error(STATUS_CMD_UNKNOWN, statement, error.c_str());

tests/checks/command-not-found.fish

@@ -21,4 +21,10 @@ $fish -C 'functions --erase fish_command_not_found' -c 'nonexistent-command appl
 #CHECKERR: nonexistent-command apple friday
 #CHECKERR: ^
 
+{ echo; echo }
+# CHECKERR: {{.*}}: Unknown command: '{ echo; echo }'
+# CHECKERR: {{.*}}: '{ ... }' is not supported for grouping commands. Please use 'begin; ...; end'
+# CHECKERR: { echo; echo }
+# CHECKERR: ^
+
 exit 0