Clean up str append/prepend a little (nushell#797)

- Move to directory for other `str` contributions
- Add simple `help` docs
- Simplify type check since only 2 cases are possible

@savente93 Are these okay?

stdlib-candidate/std-rfc/mod.nu

@@ -1,6 +1,6 @@
 # modules
 export module record/
-export module str.nu
+export module str/
 # commands
 export use fs.nu *
 export use set-env.nu *

stdlib-candidate/std-rfc/set-env.nu

@@ -13,25 +13,25 @@
 # Add a config hook
 # > set-env -a config.hooks.pre_prompt 'ellie | print'
 export def --env main [
- field: cell-path # The environment variable name or nested option cell path
- value: any # The value to set or append
- --append (-a) # Append to the previous value or wrap in a new list
+  field: cell-path # The environment variable name or nested option cell path
+  value: any # The value to set or append
+  --append (-a) # Append to the previous value or wrap in a new list
 ]: nothing -> nothing {
- def 'get or' [default field] {
- get --ignore-errors $field | default $default
- }
- let value = if $append {
- $env | get or [] $field | append $value
- } else {
- $value
- }
- let field = $field | to text | split row .
- let value = match $field {
- [_] => $value
- [$root, ..$field] => {
- let field = $field | into cell-path
- $env | get or {} $root | upsert $field $value
+ def 'get or' [default field] {
+ get --ignore-errors $field | default $default
  }
- }
- load-env { ($field | first): $value }
+ let value = if $append {
+ $env | get or [] $field | append $value
+ } else {
+ $value
+ }
+ let field = $field | to text | split row .
+ let value = match $field {
+ [_] => $value
+ [$root, ..$field] => {
+ let field = $field | into cell-path
+ $env | get or {} $root | upsert $field $value
+ }
+ }
+ load-env { ($field | first): $value }
 }

stdlib-candidate/std-rfc/str/mod.nu

@@ -0,0 +1 @@
+export use xpend.nu *

stdlib-candidate/std-rfc/str/xpend.nu

@@ -0,0 +1,39 @@
+# Append a suffix to an input string or list of strings.
+#
+# Examples:
+# Output 'hello world'
+# > 'hello' | str append ' world'
+#
+# Output file names suffixed with '_world'
+# > ls | get name | str append _world
+export def append [
+ suffix: string
+]: [string -> string, list<string> -> list<string>] {
+ let input = $in
+ let append = { $in + $suffix }
+ if ($input | describe) == string {
+ $input | do $append
+ } else {
+ $input | each $append
+ }
+}
+
+# Prepend a prefix to an input string or list of strings.
+#
+# Examples:
+# Output 'hello world'
+# > 'world' | str prepend 'hello '
+#
+# Output file names prefixed with 'hello_'
+# > ls | get name | str prepend hello_
+export def prepend [
+ prefix: string
+]: [string -> string, list<string> -> list<string>] {
+ let input = $in
+ let prepend = { $prefix + $in }
+ if ($input | describe) == string {
+ $input | do $prepend
+ } else {
+ $input | each $prepend
+ }
+}

stdlib-candidate/tests/mod.nu

@@ -1,3 +1,3 @@
 export module fs.nu
 export module record.nu
-export module str.nu
+export module str_xpend.nu