From 1eddd30f79c116728d67f3f80b2ad677bf6ed232 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Franti=C5=A1ek=20Mik=C5=A1?=
 <54376466+fananek@users.noreply.github.com>
Date: Mon, 6 Mar 2023 22:26:40 +0100
Subject: [PATCH] add isEmpty tag (#118)

---
 Sources/LeafKit/LeafSyntax/LeafTag.swift | 10 ++++++++
 Tests/LeafKitTests/TagTests.swift        | 32 ++++++++++++++++++++++++
 2 files changed, 42 insertions(+)

diff --git a/Sources/LeafKit/LeafSyntax/LeafTag.swift b/Sources/LeafKit/LeafSyntax/LeafTag.swift
index 09a7d89..c8fa105 100644
--- a/Sources/LeafKit/LeafSyntax/LeafTag.swift
+++ b/Sources/LeafKit/LeafSyntax/LeafTag.swift
@@ -14,6 +14,7 @@ public var defaultTags: [String: LeafTag] = [
     "uppercased": Uppercased(),
     "capitalized": Capitalized(),
     "contains": Contains(),
+    "isEmpty": IsEmpty(),
     "date": DateTag(),
     "count": Count(),
     "comment": Comment(),
@@ -67,6 +68,15 @@ struct Contains: LeafTag {
     }
 }
 
+struct IsEmpty: LeafTag {
+    func render(_ ctx: LeafContext) throws -> LeafData {
+        guard let str = ctx.parameters.first?.string else {
+            throw "unable to check for empty value unexpected data"
+        }
+        return .init(.bool(str.isEmpty))
+    }
+}
+
 struct DateTag: LeafTag {
     func render(_ ctx: LeafContext) throws -> LeafData {
         let formatter = DateFormatter()
diff --git a/Tests/LeafKitTests/TagTests.swift b/Tests/LeafKitTests/TagTests.swift
index 23eb0bd..101fe1f 100644
--- a/Tests/LeafKitTests/TagTests.swift
+++ b/Tests/LeafKitTests/TagTests.swift
@@ -117,6 +117,38 @@ class TagTests: XCTestCase {
         """
         try XCTAssertEqual(render(template, ["core": ["Tanner", "Logan", "Gwynne", "Siemen", "Tim"]]), expected)
     }
+    
+    func testIsEmpty() throws {
+        let template = """
+        #if(isEmpty(emptyString)):
+            This is an empty string.
+        #endif
+        """
+
+        let expected = """
+
+            This is an empty string.
+
+        """
+        try XCTAssertEqual(render(template, ["emptyString": ""]), expected)
+    }
+    
+    func testIsEmptyFalseCase() throws {
+        let template = """
+        #if(isEmpty(nonEmptyString)):
+            This is an empty string.
+        #else:
+            This is not an empty string.
+        #endif
+        """
+
+        let expected = """
+
+            This is not an empty string.
+
+        """
+        try XCTAssertEqual(render(template, ["nonEmptyString": "I'm not empty."]), expected)
+    }
 
     func testContainsTagWithHTML() throws {
         let template = """