From cfd2e00ebb9f0f76642df5fcccee25a74edd5f7f Mon Sep 17 00:00:00 2001
From: Connor Skees <connor1skees@gmail.com>
Date: Thu, 30 Jul 2020 18:35:34 -0400
Subject: [PATCH] respect `$module` argument to `mixin-exists`

---
 src/builtin/functions/meta.rs | 42 ++++++++++++++++++++++++++---------
 src/builtin/modules/mod.rs    |  4 ++++
 src/scope.rs                  |  2 +-
 tests/meta-module.rs          | 12 ++++++++++
 4 files changed, 48 insertions(+), 12 deletions(-)

diff --git a/src/builtin/functions/meta.rs b/src/builtin/functions/meta.rs
index 858f829..917ee35 100644
--- a/src/builtin/functions/meta.rs
+++ b/src/builtin/functions/meta.rs
@@ -110,19 +110,39 @@ pub(crate) fn global_variable_exists(
     }
 }
 
-// todo: should check for module arg (as well as several others)
 pub(crate) fn mixin_exists(mut args: CallArgs, parser: &mut Parser<'_>) -> SassResult<Value> {
     args.max_args(2)?;
-    match args.get_err(0, "name")? {
-        Value::String(s, _) => Ok(Value::bool(
-            parser.scopes.mixin_exists(s.into(), parser.global_scope),
-        )),
-        v => Err((
-            format!("$name: {} is not a string.", v.inspect(args.span())?),
-            args.span(),
-        )
-            .into()),
-    }
+    let name: Identifier = match args.get_err(0, "name")? {
+        Value::String(s, _) => s.into(),
+        v => {
+            return Err((
+                format!("$name: {} is not a string.", v.inspect(args.span())?),
+                args.span(),
+            )
+                .into())
+        }
+    };
+
+    let module = match args.default_arg(1, "module", Value::Null)? {
+        Value::String(s, _) => Some(s),
+        Value::Null => None,
+        v => {
+            return Err((
+                format!("$module: {} is not a string.", v.inspect(args.span())?),
+                args.span(),
+            )
+                .into())
+        }
+    };
+
+    Ok(Value::bool(if let Some(module_name) = module {
+        parser
+            .modules
+            .get(module_name.into(), args.span())?
+            .mixin_exists(name)
+    } else {
+        parser.scopes.mixin_exists(name, parser.global_scope)
+    }))
 }
 
 pub(crate) fn function_exists(mut args: CallArgs, parser: &mut Parser<'_>) -> SassResult<Value> {
diff --git a/src/builtin/modules/mod.rs b/src/builtin/modules/mod.rs
index 30f153e..21e6d6c 100644
--- a/src/builtin/modules/mod.rs
+++ b/src/builtin/modules/mod.rs
@@ -65,6 +65,10 @@ impl Module {
         self.0.functions.get(&name).cloned()
     }
 
+    pub fn mixin_exists(&self, name: Identifier) -> bool {
+        self.0.mixin_exists(name)
+    }
+
     pub fn insert_builtin(
         &mut self,
         name: &'static str,
diff --git a/src/scope.rs b/src/scope.rs
index ddf3340..7583151 100644
--- a/src/scope.rs
+++ b/src/scope.rs
@@ -55,7 +55,7 @@ impl Scope {
         self.mixins.insert(s.into(), v)
     }
 
-    fn mixin_exists(&self, name: Identifier) -> bool {
+    pub fn mixin_exists(&self, name: Identifier) -> bool {
         self.mixins.contains_key(&name)
     }
 
diff --git a/tests/meta-module.rs b/tests/meta-module.rs
index da5b626..5e3310b 100644
--- a/tests/meta-module.rs
+++ b/tests/meta-module.rs
@@ -1,5 +1,7 @@
 #![cfg(test)]
 
+use std::io::Write;
+
 #[macro_use]
 mod macros;
 
@@ -13,3 +15,13 @@ test!(
     "@use 'sass:meta';\n@use 'sass:math';\na {\n  color: inspect(meta.module-variables(math));\n}\n",
     "a {\n  color: (\"e\": 2.7182818285, \"pi\": 3.1415926536);\n}\n"
 );
+
+#[test]
+fn mixin_exists_module() {
+    let input = "@use \"mixin_exists_module\" as module;\na {\n color: mixin-exists(foo, $module: module);\n}";
+    tempfile!("mixin_exists_module.scss", "@mixin foo {}");
+    assert_eq!(
+        "a {\n  color: true;\n}\n",
+        &grass::from_string(input.to_string(), &grass::Options::default()).expect(input)
+    );
+}