add get_env function to yuck (#779)

* added basic get_env function to yuck

* added get_env to changelog

* added get_env to docs

* changed key to string in doc

* changed suggested code

* credit myself in CHANGELOG.md

CHANGELOG.md

@@ -15,6 +15,7 @@ All notable changes to eww will be listed here, starting at changes since versio
 - Remove `eww windows` command, replace with `eww active-windows` and `eww list-windows`
 
 ### Features
+- Add `get_env` function (By: RegenJacob)
 - Add `:namespace` window option
 - Default to building with x11 and wayland support simultaneously
 - Add `truncate-left` property on `label` widgets (By: kawaki-san)

crates/simplexpr/src/eval.rs

@@ -313,6 +313,13 @@ impl SimplExpr {
 
 fn call_expr_function(name: &str, args: Vec<DynVal>) -> Result<DynVal, EvalError> {
     match name {
+        "get_env" => match args.as_slice() {
+            [var_name] => {
+                let var = std::env::var(var_name.as_string()?).unwrap_or_default();
+                Ok(DynVal::from(var))
+            }
+            _ => Err(EvalError::WrongArgCount(name.to_string())),
+        },
         "round" => match args.as_slice() {
             [num, digits] => {
                 let num = num.as_f64()?;

docs/src/expression_language.md

@@ -51,11 +51,12 @@ Supported currently are the following features:
 	- `arraylength(value)`: Gets the length of the array
 	- `objectlength(value)`: Gets the amount of entries in the object
 	- `jq(value, jq_filter_string)`: run a [jq](https://stedolan.github.io/jq/manual/) style command on a json value. (Uses [jaq](https://crates.io/crates/jaq) internally).
-    - `formattime(unix_timestamp, format_str, timezone)`: Gets the time in a given format from UNIX timestamp.
-      Check [chrono's documentation](https://docs.rs/chrono/latest/chrono/format/strftime/index.html) for more
-      information about format string and [chrono-tz's documentation](https://docs.rs/chrono-tz/latest/chrono_tz/enum.Tz.html)
-      for available time zones.
-    - `formattime(unix_timestamp, format_str)`: Gets the time in a given format from UNIX timestamp.
-      Same as other `formattime`, but does not accept timezone. Instead, it uses system's local timezone.
-      Check [chrono's documentation](https://docs.rs/chrono/latest/chrono/format/strftime/index.html) for more
-      information about format string.
+  - `get_env(string)`: Gets the specified enviroment variable
+  - `formattime(unix_timestamp, format_str, timezone)`: Gets the time in a given format from UNIX timestamp.
+     Check [chrono's documentation](https://docs.rs/chrono/latest/chrono/format/strftime/index.html) for more
+     information about format string and [chrono-tz's documentation](https://docs.rs/chrono-tz/latest/chrono_tz/enum.Tz.html)
+     for available time zones.
+  - `formattime(unix_timestamp, format_str)`: Gets the time in a given format from UNIX timestamp.
+     Same as other `formattime`, but does not accept timezone. Instead, it uses system's local timezone.
+     Check [chrono's documentation](https://docs.rs/chrono/latest/chrono/format/strftime/index.html) for more
+     information about format string.