Rewrite builtin functions in rust

tests/checks/functions.fish

@@ -9,6 +9,10 @@ end
 functions    --details f1 f2
 #CHECKERR: functions: --details: expected 1 arguments; got 2
 
+# Verify that it still mentions "--details" even if it isn't the last option.
+functions    --details --verbose f1 f2
+#CHECKERR: functions: --details: expected 1 arguments; got 2
+
 # ==========
 # Verify that `functions --details` works as expected when given the name of a
 # known function.
@@ -185,3 +189,38 @@ functions --handlers-type signal
 # CHECK: SIGTERM term1
 # CHECK: SIGTERM term2
 # CHECK: SIGTERM term3
+
+# See how --names and --all work.
+# We don't want to list all of our functions here,
+# so we just match a few that we know are there.
+functions -n | string match cd
+# CHECK: cd
+
+functions --names | string match __fish_config_interactive
+echo $status
+# CHECK: 1
+
+functions --names -a | string match __fish_config_interactive
+# CHECK: __fish_config_interactive
+
+functions --description ""
+# CHECKERR: functions: Expected exactly one function name
+# CHECKERR: checks/functions.fish (line {{\d+}}):
+# CHECKERR: functions --description ""
+# CHECKERR: ^
+# CHECKERR: (Type 'help functions' for related documentation)
+
+function foo --on-variable foo; end
+# This should print *everything*
+functions --handlers-type "" | string match 'Event *'
+# CHECK: Event signal
+# CHECK: Event variable
+# CHECK: Event generic
+functions -e foo
+
+functions --details --verbose thisfunctiondoesnotexist
+# CHECK: n/a
+# CHECK: n/a
+# CHECK: 0
+# CHECK: n/a
+# CHECK: n/a

tests/pexpects/generic.py

@@ -64,3 +64,8 @@ expect_str("# Defined interactively\r\n")
 expect_str("function foo")
 expect_str("end")
 expect_prompt()
+
+# See that `functions` terminates
+sendline("functions")
+expect_re(".*fish_prompt,.*")
+expect_prompt()