From 52bf3f0091a7e7ba2d3e6a927d3b099a200df846 Mon Sep 17 00:00:00 2001
From: ConnorSkees <39542938+ConnorSkees@users.noreply.github.com>
Date: Sat, 20 Jun 2020 22:29:35 -0400
Subject: [PATCH] implement short circuiting for `and`

---
 src/parse/value.rs | 25 ++++++++++++++++++++-----
 tests/and.rs       |  5 +++++
 2 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/src/parse/value.rs b/src/parse/value.rs
index 09fd33c..86fee64 100644
--- a/src/parse/value.rs
+++ b/src/parse/value.rs
@@ -895,11 +895,26 @@ impl<'a, 'b: 'a> IntermediateValueIterator<'a, 'b> {
                         .push(Value::String(op.to_string(), QuoteKind::None).span(op.span));
                 } else if let Some(left) = space_separated.pop() {
                     self.whitespace();
-                    let right = self.single_value()?;
-                    space_separated.push(
-                        Value::BinaryOp(Box::new(left.node), op.node, Box::new(right.node))
-                            .span(left.span.merge(right.span)),
-                    );
+                    if left.node.is_true(left.span)? {
+                        let right = self.single_value()?;
+                        space_separated.push(
+                            Value::BinaryOp(Box::new(left.node), op.node, Box::new(right.node))
+                                .span(left.span.merge(right.span)),
+                        );
+                    } else {
+                        // we explicitly ignore errors here as a workaround for short circuiting
+                        while let Some(value) = self.peek() {
+                            if let Ok(Spanned {
+                                node: IntermediateValue::Comma,
+                                ..
+                            }) = value
+                            {
+                                break;
+                            }
+                            self.next();
+                        }
+                        space_separated.push(left);
+                    }
                 } else {
                     return Err(("Expected expression.", op.span).into());
                 }
diff --git a/tests/and.rs b/tests/and.rs
index dd48b9f..a3d9e4a 100644
--- a/tests/and.rs
+++ b/tests/and.rs
@@ -51,3 +51,8 @@ test!(
     "a {\n  color: 1 - AND;\n}\n",
     "a {\n  color: 1-AND;\n}\n"
 );
+test!(
+    short_circuits_when_lhs_is_false,
+    "a {\n  color: false and comparable(\"a\", \"b\");\n}\n",
+    "a {\n  color: false;\n}\n"
+);