SPIGOT-5240: Vector.angle not valid for angles very close to each other

By: md_5 <git@md-5.net>

paper-api/src/main/java/org/bukkit/util/Vector.java

@@ -1,6 +1,7 @@
 package org.bukkit.util;
 
 import com.google.common.base.Preconditions;
+import com.google.common.primitives.Doubles;
 import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.Random;
@@ -202,7 +203,7 @@ public class Vector implements Cloneable, ConfigurationSerializable {
      * @return angle in radians
      */
     public float angle(@NotNull Vector other) {
-        double dot = dot(other) / (length() * other.length());
+        double dot = Doubles.constrainToRange(dot(other) / (length() * other.length()), -1.0, 1.0);
 
         return (float) Math.acos(dot);
     }

paper-api/src/test/java/org/bukkit/util/VectorTest.java

@@ -114,4 +114,12 @@ public class VectorTest {
             assertEquals(a, v.angle(axis), Vector.getEpsilon());
         }
     }
+
+    @Test
+    public void testSmallAngle() {
+        Vector a = new Vector(-0.13154885489775203, 0.0, 0.12210868381700482);
+        Vector b = new Vector(-0.7329152226448059, -0.0, 0.6803199648857117);
+
+        assertTrue(Double.isFinite(a.angle(b)));
+    }
 }