Add (variable|function|mixin)-exists builtin functions

src/builtin/color.rs

@@ -10,7 +10,7 @@ use crate::units::Unit;
 use crate::value::Value;
 
 pub(crate) fn register(f: &mut BTreeMap<String, Builtin>) {
-    decl!(f "rgb", |args| {
+    decl!(f "rgb", |args, _| {
         let channels = args.get("channels").unwrap_or(&Value::Null);
         if channels.is_null() {
             let red: u16 = arg!(args, 0, "red").clone().try_into().unwrap();
@@ -21,19 +21,19 @@ pub(crate) fn register(f: &mut BTreeMap<String, Builtin>) {
             todo!("channels variable in `rgb`")
         }
     });
-    decl!(f "red", |args| {
+    decl!(f "red", |args, _| {
         match arg!(args, 0, "red") {
             Value::Color(c) => Some(Value::Dimension(BigRational::from_integer(BigInt::from(c.red())), Unit::None)),
             _ => todo!("non-color given to builtin function `red()`")
         }
     });
-    decl!(f "green", |args| {
+    decl!(f "green", |args, _| {
         match arg!(args, 0, "green") {
             Value::Color(c) => Some(Value::Dimension(BigRational::from_integer(BigInt::from(c.green())), Unit::None)),
             _ => todo!("non-color given to builtin function `green()`")
         }
     });
-    decl!(f "blue", |args| {
+    decl!(f "blue", |args, _| {
         match arg!(args, 0, "blue") {
             Value::Color(c) => Some(Value::Dimension(BigRational::from_integer(BigInt::from(c.blue())), Unit::None)),
             _ => todo!("non-color given to builtin function `blue()`")

src/builtin/meta.rs

@@ -6,7 +6,7 @@ use crate::units::Unit;
 use crate::value::Value;
 
 pub(crate) fn register(f: &mut BTreeMap<String, Builtin>) {
-    decl!(f "if", |args| {
+    decl!(f "if", |args, _| {
         let cond: &Value = arg!(args, 0, "condition");
         let if_true = arg!(args, 1, "if-true").clone();
         let if_false = arg!(args, 2, "if-false").clone();
@@ -16,7 +16,7 @@ pub(crate) fn register(f: &mut BTreeMap<String, Builtin>) {
             Some(if_false)
         }
     });
-    decl!(f "feature-exists", |args| {
+    decl!(f "feature-exists", |args, _| {
         let feature: &Value = arg!(args, 0, "feature");
         match feature.clone().unquote().to_string().as_str() {
             // A local variable will shadow a global variable unless
@@ -37,7 +37,7 @@ pub(crate) fn register(f: &mut BTreeMap<String, Builtin>) {
             _ => Some(Value::False),
         }
     });
-    decl!(f "unit", |args| {
+    decl!(f "unit", |args, _| {
         let number = arg!(args, 0, "number");
         let unit = match number {
             Value::Dimension(_, u) => u.to_string(),
@@ -45,11 +45,11 @@ pub(crate) fn register(f: &mut BTreeMap<String, Builtin>) {
         };
         Some(Value::Ident(unit, QuoteKind::Double))
     });
-    decl!(f "type-of", |args| {
+    decl!(f "type-of", |args, _| {
         let value = arg!(args, 0, "value");
         Some(Value::Ident(value.kind().to_owned(), QuoteKind::None))
     });
-    decl!(f "unitless", |args| {
+    decl!(f "unitless", |args, _| {
         let number = arg!(args, 0, "number");
         match number {
             Value::Dimension(_, Unit::None) => Some(Value::True),
@@ -57,8 +57,20 @@ pub(crate) fn register(f: &mut BTreeMap<String, Builtin>) {
             _ => Some(Value::True)
         }
     });
-    decl!(f "inspect", |args| {
+    decl!(f "inspect", |args, _| {
         let value = arg!(args, 0, "value");
         Some(Value::Ident(value.to_string(), QuoteKind::None))
     });
+    decl!(f "variable-exists", |args, scope| {
+        let value = arg!(args, 0, "name");
+        Some(Value::bool(scope.var_exists(&value.to_string())))
+    });
+    decl!(f "mixin-exists", |args, scope| {
+        let value = arg!(args, 0, "name");
+        Some(Value::bool(scope.mixin_exists(&value.to_string())))
+    });
+    decl!(f "function-exists", |args, scope| {
+        let value = arg!(args, 0, "name");
+        Some(Value::bool(scope.fn_exists(&value.to_string())))
+    });
 }

src/builtin/mod.rs

@@ -2,6 +2,7 @@ use lazy_static::lazy_static;
 use std::collections::BTreeMap;
 
 use crate::args::CallArgs;
+use crate::common::Scope;
 use crate::value::Value;
 
 #[macro_use]
@@ -15,7 +16,7 @@ mod meta;
 mod selector;
 mod string;
 
-pub(crate) type Builtin = Box<dyn Fn(&CallArgs) -> Option<Value> + Send + Sync>;
+pub(crate) type Builtin = Box<dyn Fn(&CallArgs, &Scope) -> Option<Value> + Send + Sync>;
 
 lazy_static! {
     pub(crate) static ref GLOBAL_FUNCTIONS: BTreeMap<String, Builtin> = {

src/value/parse.rs

@@ -200,7 +200,7 @@ impl Value {
                         let func = match scope.get_fn(&s) {
                             Ok(f) => f,
                             Err(_) => match GLOBAL_FUNCTIONS.get(&s) {
-                                Some(f) => return f(&args),
+                                Some(f) => return f(&args, scope),
                                 None => todo!("called undefined function"),
                             },
                         };

tests/meta.rs

@@ -229,6 +229,51 @@ test!(
     "a {\n  color: inspect(null)\n}\n",
     "a {\n  color: null;\n}\n"
 );
+test!(
+    variable_does_exist,
+    "$a: red; a {\n  color: variable-exists(a)\n}\n",
+    "a {\n  color: true;\n}\n"
+);
+test!(
+    variable_does_not_exist,
+    "a {\n  color: variable-exists(a)\n}\n",
+    "a {\n  color: false;\n}\n"
+);
+test!(
+    variable_exists_named,
+    "$a: red; a {\n  color: variable-exists($name: a)\n}\n",
+    "a {\n  color: true;\n}\n"
+);
+test!(
+    mixin_does_exist,
+    "@mixin a{} a {\n  color: mixin-exists(a)\n}\n",
+    "a {\n  color: true;\n}\n"
+);
+test!(
+    mixin_does_not_exist,
+    "a {\n  color: mixin-exists(a)\n}\n",
+    "a {\n  color: false;\n}\n"
+);
+test!(
+    mixin_exists_named,
+    "@mixin a{} a {\n  color: mixin-exists($name: a)\n}\n",
+    "a {\n  color: true;\n}\n"
+);
+test!(
+    function_does_exist,
+    "@function a(){} a {\n  color: function-exists(a)\n}\n",
+    "a {\n  color: true;\n}\n"
+);
+test!(
+    function_does_not_exist,
+    "a {\n  color: function-exists(a)\n}\n",
+    "a {\n  color: false;\n}\n"
+);
+test!(
+    function_exists_named,
+    "@function a(){} a {\n  color: function-exists($name: a)\n}\n",
+    "a {\n  color: true;\n}\n"
+);
 // test!(
 //     inspect_empty_list,
 //     "a {\n  color: inspect(())\n}\n",