Add with function

CHANGELOG.md

@@ -13,7 +13,7 @@ All notable changes to eww will be listed here, starting at changes since versio
 - Add support for `:hover` css selectors for eventbox (By: druskus20)
 - Add `eww get` subcommand (By: druskus20)
 - Add circular progress widget (By: druskus20)
-- Add `search` and `captures` functions for expressions (By: MartinJM)
+- Add `search`, `captures`, and `with` functions for expressions (By: MartinJM)
 
 ### Notable Internal changes
 - Rework state management completely, now making local state and dynamic widget hierarchy changes possible.

crates/simplexpr/src/eval.rs

@@ -1,3 +1,4 @@
+use crate::parse_string;
 use itertools::Itertools;
 
 use crate::{
@@ -27,6 +28,9 @@ pub enum EvalError {
     #[error("Unknown function {0}")]
     UnknownFunction(String),
 
+    #[error("Invalid expression for with: {0}")]
+    InvalidWithExpression(String),
+
     #[error("Unable to index into value {0}")]
     CannotIndex(String),
 
@@ -330,6 +334,17 @@ fn call_expr_function(name: &str, args: Vec<DynVal>) -> Result<DynVal, EvalError
             }
             _ => Err(EvalError::WrongArgCount(name.to_string())),
         },
+        "with" => match args.as_slice() {
+            [varname, value, function] => {
+                let mut valuemap = HashMap::new();
+                valuemap.insert(VarName(varname.to_string()), value.clone());
+                match parse_string(0, 0, &function.as_string()?) {
+                    Ok(p) => p.eval(&valuemap),
+                    Err(_) => Err(EvalError::InvalidWithExpression(function.as_string()?)),
+                }
+            }
+            _ => Err(EvalError::WrongArgCount(name.to_string())),
+        },
         _ => Err(EvalError::UnknownFunction(name.to_string())),
     }
 }

docs/src/expression_language.md

@@ -34,4 +34,5 @@ Supported currently are the following features:
     - `replace(string, regex, replacement)`: Replace matches of a given regex in a string
 	- `search(string, regex)`: Search for a given regex in a string (returns json)
 	- `captures(string, regex)`: Get the captures of a given regex in a string (returns json)
+	- `with(name, value, expression)`: Evaluate the simple expression (which must be a string), where the variable `name` has value `value`