fix(join): Dont force strings

Sources/Filters.swift

@@ -47,17 +47,17 @@ func defaultFilter(value: Any?, arguments: [Any?]) -> Any? {
 }
 
 func joinFilter(value: Any?, arguments: [Any?]) throws -> Any? {
-  guard arguments.count == 1 else {
+  guard arguments.count < 2 else {
     throw TemplateSyntaxError("'join' filter takes a single argument")
   }
 
-  guard let separator = arguments.first as? String else {
+  let separator = stringify(arguments.first ?? "")
-    throw TemplateSyntaxError("'join' filter takes a separator as string")
+
+  if let value = value as? [Any] {
+    return value
+      .map(stringify)
+      .joined(separator: separator)
   }
 
-  if let value = value as? [String] {
+  return value
-    return value.joined(separator: separator)
-  }
-
-  return nil
 }

Tests/StencilTests/FilterSpec.swift

@@ -125,9 +125,26 @@ func testFilter() {
   describe("join filter") {
     let template = Template(templateString: "{{ value|join:\", \" }}")
 
-    $0.it("transforms a string to be lowercase") {
+    $0.it("joins a collection of strings") {
       let result = try template.render(Context(dictionary: ["value": ["One", "Two"]]))
       try expect(result) == "One, Two"
     }
+
+    $0.it("joins a mixed-type collection") {
+      let result = try template.render(Context(dictionary: ["value": ["One", 2, true, 10.5, "Five"]]))
+      try expect(result) == "One, 2, true, 10.5, Five"
+    }
+
+    $0.it("can join by non string") {
+      let template = Template(templateString: "{{ value|join:separator }}")
+      let result = try template.render(Context(dictionary: ["value": ["One", "Two"], "separator": true]))
+      try expect(result) == "OnetrueTwo"
+    }
+
+    $0.it("can join without arguments") {
+      let template = Template(templateString: "{{ value|join }}")
+      let result = try template.render(Context(dictionary: ["value": ["One", "Two"]]))
+      try expect(result) == "OneTwo"
+    }
   }
 }

docs/builtins.rst

@@ -279,10 +279,10 @@ value of the variable. For example:
 ``join``
 ~~~~~~~~
 
-Join an array with a string.
+Join an array of items.
 
 .. code-block:: html+django
 
     {{ value|join:", " }}
 
-.. note:: The value MUST be an array of Strngs and the separator must be a string.
+.. note:: The value MUST be an array.