Custom command attributes (#14906)

# Description
Add custom command attributes.

- Attributes are placed before a command definition and start with a `@`
character.
- Attribute invocations consist of const command call. The command's
name must start with "attr ", but this prefix is not used in the
invocation.
- A command named `attr example` is invoked as an attribute as
`@example`
-   Several built-in attribute commands are provided as part of this PR
    -   `attr example`: Attaches an example to the commands help text
        ```nushell
        # Double numbers
        @example "double an int"  { 5 | double }   --result 10
        @example "double a float" { 0.5 | double } --result 1.0
        def double []: [number -> number] {
            $in * 2
        }
        ```
    -   `attr search-terms`: Adds search terms to a command
    -   ~`attr env`: Equivalent to using `def --env`~
- ~`attr wrapped`: Equivalent to using `def --wrapped`~ shelved for
later discussion
    -   several testing related attributes in `std/testing`
- If an attribute has no internal/special purpose, it's stored as
command metadata that can be obtained with `scope commands`.
- This allows having attributes like `@test` which can be used by test
runners.
-   Used the `@example` attribute for `std` examples.
-   Updated the std tests and test runner to use `@test` attributes
-   Added completions for attributes

# User-Facing Changes
Users can add examples to their own command definitions, and add other
arbitrary attributes.

# Tests + Formatting

- 🟢 toolkit fmt
- 🟢 toolkit clippy
- 🟢 toolkit test
- 🟢 toolkit test stdlib

# After Submitting
- Add documentation about the attribute syntax and built-in attributes
- `help attributes`

---------

Co-authored-by: 132ikl <132@ikl.sh>

crates/nu-std/tests/logger_tests/test_basic_commands.nu

@@ -1,3 +1,4 @@
+use std/testing *
 use std/assert
 
 def run [
@@ -41,57 +42,57 @@ def "assert message short" [
     assert str contains $output "test message"
 }
 
-#[test]
+@test
 def critical [] {
     assert no message 99 critical
     assert message CRITICAL critical CRT
 }
 
-#[test]
+@test
 def critical_short [] {
     assert message short CRITICAL critical C
 }
 
-#[test]
+@test
 def error [] {
     assert no message CRITICAL error
     assert message ERROR error ERR
 }
 
-#[test]
+@test
 def error_short [] {
     assert message short ERROR error E
 }
 
-#[test]
+@test
 def warning [] {
     assert no message ERROR warning
     assert message WARNING warning WRN
 }
 
-#[test]
+@test
 def warning_short [] {
     assert message short WARNING warning W
 }
 
-#[test]
+@test
 def info [] {
     assert no message WARNING info
     assert message INFO info "INF" # INF has to be quoted, otherwise it is the `inf` float
 }
 
-#[test]
+@test
 def info_short [] {
     assert message short INFO info I
 }
 
-#[test]
+@test
 def debug [] {
     assert no message INFO debug
     assert message DEBUG debug DBG
 }
 
-#[test]
+@test
 def debug_short [] {
     assert message short DEBUG debug D
 }

crates/nu-std/tests/logger_tests/test_log_custom.nu

@@ -1,3 +1,4 @@
+use std/testing *
 use std/assert
 use commons.nu *
 
@@ -21,14 +22,14 @@ def run-command [
     | complete | get --ignore-errors stderr
 }
 
-#[test]
+@test
 def errors_during_deduction [] {
     assert str contains (run-command "DEBUG" "msg" "%MSG%" 25) "Cannot deduce log level prefix for given log level"
     assert str contains (run-command "DEBUG" "msg" "%MSG%" 25 --ansi (ansi red)) "Cannot deduce log level prefix for given log level"
     assert str contains (run-command "DEBUG" "msg" "%MSG%" 25 --level-prefix "abc") "Cannot deduce ansi for given log level"
 }
 
-#[test]
+@test
 def valid_calls [] {
     use std/log *
     assert equal (run-command "DEBUG" "msg" "%MSG%" 25 --level-prefix "abc" --ansi (ansi default) | str trim --right) "msg"
@@ -37,7 +38,7 @@ def valid_calls [] {
     assert equal (run-command "INFO" "msg" "%ANSI_START%%LEVEL% %MSG%%ANSI_STOP%" ((log-level).CRITICAL) | str trim --right) $"((log-ansi).CRITICAL)CRT msg(ansi reset)"
 }
 
-#[test]
+@test
 def log-level_handling [] {
     use std/log *
     assert equal (run-command "DEBUG" "msg" "%LEVEL% %MSG%" 20 | str trim --right) $"((log-prefix).INFO) msg"

crates/nu-std/tests/logger_tests/test_log_format_flag.nu

@@ -1,3 +1,4 @@
+use std/testing *
 use std *
 use std/log *
 use std/assert
@@ -40,7 +41,7 @@ def "assert formatted" [
     assert equal ($output | str trim --right) (format-message $message $format $prefix $ansi)
 }
 
-#[test]
+@test
 def format_flag [] {
     assert formatted "test" "25 %MSG% %ANSI_START% %LEVEL%%ANSI_STOP%" critical
     assert formatted "test" "25 %MSG% %ANSI_START% %LEVEL%%ANSI_STOP%" error

crates/nu-std/tests/logger_tests/test_logger_env.nu

@@ -1,8 +1,9 @@
+use std/testing *
 use std/assert
 use std/log
 use std/log *
 
-#[test]
+@test
 def env_log-ansi [] {
     assert equal (log-ansi).CRITICAL (ansi red_bold)
     assert equal (log-ansi).ERROR (ansi red)
@@ -11,7 +12,7 @@ def env_log-ansi [] {
     assert equal (log-ansi).DEBUG (ansi default_dimmed)
 }
 
-#[test]
+@test
 def env_log-level [] {
     assert equal (log-level).CRITICAL 50
     assert equal (log-level).ERROR 40
@@ -20,7 +21,7 @@ def env_log-level [] {
     assert equal (log-level).DEBUG 10
 }
 
-#[test]
+@test
 def env_log-prefix [] {
     assert equal (log-prefix).CRITICAL "CRT"
     assert equal (log-prefix).ERROR "ERR"
@@ -29,7 +30,7 @@ def env_log-prefix [] {
     assert equal (log-prefix).DEBUG "DBG"
 }
 
-#[test]
+@test
 def env_log-short-prefix [] {
     assert equal (log-short-prefix).CRITICAL "C"
     assert equal (log-short-prefix).ERROR "E"
@@ -38,7 +39,7 @@ def env_log-short-prefix [] {
     assert equal (log-short-prefix).DEBUG "D"
 }
 
-#[test]
+@test
 def env_log_format [] {
     assert equal $env.NU_LOG_FORMAT $"%ANSI_START%%DATE%|%LEVEL%|%MSG%%ANSI_STOP%"
 }