AttributeContainer Filtering (#1182)

Author: jmschonfeld

Sources/FoundationEssentials/AttributedString/AttributeContainer.swift

@@ -104,3 +104,31 @@ extension AttributeContainer {
         storage.hasConstrainedAttributes
     }
 }
+
+@available(FoundationPreview 6.2, *)
+extension AttributeContainer {
+    /// Returns an attribute container storing only the attributes in `self` with the `inheritedByAddedText` property set to `true`
+    public func filter(inheritedByAddedText: Bool) -> AttributeContainer {
+        var storage = self.storage
+        for (key, value) in storage.contents {
+            let inherited = value.inheritedByAddedText && !value.isInvalidatedOnTextChange
+            if inherited != inheritedByAddedText {
+                storage[key] = nil
+            }
+        }
+        return AttributeContainer(storage)
+    }
+    
+    /// Returns an attribute container storing only the attributes in `self` with a matching run boundary property
+    ///
+    /// Note: if `nil` is provided then only attributes not bound to any particular boundary will be returned
+    public func filter(runBoundaries: AttributedString.AttributeRunBoundaries?) -> AttributeContainer {
+        var storage = self.storage
+        for (key, value) in storage.contents {
+            if value.runBoundaries != runBoundaries {
+                storage[key] = nil
+            }
+        }
+        return AttributeContainer(storage)
+    }
+}

Tests/FoundationEssentialsTests/AttributedString/AttributedStringTests.swift

@@ -2578,4 +2578,25 @@ E {
             }
         }
     }
+    
+    func testAttributeContainerFiltering() {
+        XCTAssertEqual(AttributeContainer().filter(runBoundaries: nil), AttributeContainer())
+        XCTAssertEqual(AttributeContainer().filter(runBoundaries: .paragraph), AttributeContainer())
+        XCTAssertEqual(AttributeContainer().filter(inheritedByAddedText: true), AttributeContainer())
+        XCTAssertEqual(AttributeContainer().filter(inheritedByAddedText: false), AttributeContainer())
+        
+        let testContainer = AttributeContainer.testInt(2).testBool(true).testString("Hello")
+        XCTAssertEqual(testContainer.filter(runBoundaries: nil), testContainer)
+        XCTAssertEqual(testContainer.filter(runBoundaries: .paragraph), AttributeContainer())
+        XCTAssertEqual(testContainer.filter(inheritedByAddedText: true), testContainer)
+        XCTAssertEqual(testContainer.filter(inheritedByAddedText: false), AttributeContainer())
+        
+        let testConstrainedContainer = AttributeContainer.testInt(2).testParagraphConstrained(3).testCharacterConstrained(4).testNonExtended(5)
+        XCTAssertEqual(testConstrainedContainer.filter(runBoundaries: nil), AttributeContainer.testInt(2).testNonExtended(5))
+        XCTAssertEqual(testConstrainedContainer.filter(runBoundaries: .paragraph), AttributeContainer.testParagraphConstrained(3))
+        XCTAssertEqual(testConstrainedContainer.filter(runBoundaries: .character("A")), AttributeContainer())
+        XCTAssertEqual(testConstrainedContainer.filter(runBoundaries: .character("*")), AttributeContainer.testCharacterConstrained(4))
+        XCTAssertEqual(testConstrainedContainer.filter(inheritedByAddedText: true), AttributeContainer.testInt(2).testParagraphConstrained(3).testCharacterConstrained(4))
+        XCTAssertEqual(testConstrainedContainer.filter(inheritedByAddedText: false), AttributeContainer.testNonExtended(5))
+    }
 }