feat(if): Support elif tags

CHANGELOG.md

@@ -1,5 +1,22 @@
 # Stencil Changelog
 
+## Master
+
+### Enhancements
+
+- `if` blocks may now contain else if (`elif`) conditions.
+
+  ```html+django
+  {% if one or two and not three %}
+    one or two but not three
+  {% elif four %}
+    four
+  {% else %}
+    not one, two, or four
+  {% endif %}
+  ```
+
+
 ## 0.8.0
 
 ### Breaking

Sources/IfTag.swift

@@ -186,19 +186,30 @@ class IfNode : NodeType {
     var components = token.components()
     components.removeFirst()
 
-    var conditions: [IfCondition] = []
-
     let expression = try parseExpression(components: components, tokenParser: parser)
-    let nodes = try parser.parse(until(["endif", "else"]))
-    conditions.append(IfCondition(expression: expression, nodes: nodes))
+    let nodes = try parser.parse(until(["endif", "elif", "else"]))
+    var conditions: [IfCondition] = [
+      IfCondition(expression: expression, nodes: nodes)
+    ]
 
-    guard let token = parser.nextToken() else {
-      throw TemplateSyntaxError("`endif` was not found.")
+    var token = parser.nextToken()
+    while let current = token, current.contents.hasPrefix("elif") {
+      var components = current.components()
+      components.removeFirst()
+      let expression = try parseExpression(components: components, tokenParser: parser)
+
+      let nodes = try parser.parse(until(["endif", "elif", "else"]))
+      token = parser.nextToken()
+      conditions.append(IfCondition(expression: expression, nodes: nodes))
     }
 
-    if token.contents == "else" {
+    if let current = token, current.contents == "else" {
       conditions.append(IfCondition(expression: nil, nodes: try parser.parse(until(["endif"]))))
-      _ = parser.nextToken()
+      token = parser.nextToken()
+    }
+
+    guard let current = token, current.contents == "endif" else {
+      throw TemplateSyntaxError("`endif` was not found.")
     }
 
     return IfNode(conditions: conditions)

Tests/StencilTests/IfNodeSpec.swift

@@ -48,6 +48,100 @@ func testIfNode() {
         try expect(falseNode?.text) == "false"
       }
 
+      $0.it("can parse an if with elif block") {
+        let tokens: [Token] = [
+          .block(value: "if value"),
+          .text(value: "true"),
+          .block(value: "elif something"),
+          .text(value: "some"),
+          .block(value: "else"),
+          .text(value: "false"),
+          .block(value: "endif")
+        ]
+
+        let parser = TokenParser(tokens: tokens, environment: Environment())
+        let nodes = try parser.parse()
+        let node = nodes.first as? IfNode
+
+        let conditions = node?.conditions
+        try expect(conditions?.count) == 3
+
+        try expect(conditions?[0].nodes.count) == 1
+        let trueNode = conditions?[0].nodes.first as? TextNode
+        try expect(trueNode?.text) == "true"
+
+        try expect(conditions?[1].nodes.count) == 1
+        let elifNode = conditions?[1].nodes.first as? TextNode
+        try expect(elifNode?.text) == "some"
+
+        try expect(conditions?[2].nodes.count) == 1
+        let falseNode = conditions?[2].nodes.first as? TextNode
+        try expect(falseNode?.text) == "false"
+      }
+
+      $0.it("can parse an if with elif block without else") {
+        let tokens: [Token] = [
+          .block(value: "if value"),
+          .text(value: "true"),
+          .block(value: "elif something"),
+          .text(value: "some"),
+          .block(value: "endif")
+        ]
+
+        let parser = TokenParser(tokens: tokens, environment: Environment())
+        let nodes = try parser.parse()
+        let node = nodes.first as? IfNode
+
+        let conditions = node?.conditions
+        try expect(conditions?.count) == 2
+
+        try expect(conditions?[0].nodes.count) == 1
+        let trueNode = conditions?[0].nodes.first as? TextNode
+        try expect(trueNode?.text) == "true"
+
+        try expect(conditions?[1].nodes.count) == 1
+        let elifNode = conditions?[1].nodes.first as? TextNode
+        try expect(elifNode?.text) == "some"
+      }
+
+      $0.it("can parse an if with multiple elif block") {
+        let tokens: [Token] = [
+          .block(value: "if value"),
+          .text(value: "true"),
+          .block(value: "elif something1"),
+          .text(value: "some1"),
+          .block(value: "elif something2"),
+          .text(value: "some2"),
+          .block(value: "else"),
+          .text(value: "false"),
+          .block(value: "endif")
+        ]
+
+        let parser = TokenParser(tokens: tokens, environment: Environment())
+        let nodes = try parser.parse()
+        let node = nodes.first as? IfNode
+
+        let conditions = node?.conditions
+        try expect(conditions?.count) == 4
+
+        try expect(conditions?[0].nodes.count) == 1
+        let trueNode = conditions?[0].nodes.first as? TextNode
+        try expect(trueNode?.text) == "true"
+
+        try expect(conditions?[1].nodes.count) == 1
+        let elifNode = conditions?[1].nodes.first as? TextNode
+        try expect(elifNode?.text) == "some1"
+
+        try expect(conditions?[2].nodes.count) == 1
+        let elif2Node = conditions?[2].nodes.first as? TextNode
+        try expect(elif2Node?.text) == "some2"
+
+        try expect(conditions?[3].nodes.count) == 1
+        let falseNode = conditions?[3].nodes.first as? TextNode
+        try expect(falseNode?.text) == "false"
+      }
+
+
       $0.it("can parse an if with complex expression") {
         let tokens: [Token] = [
           .block(value: "if value == \"test\" and not name"),

docs/builtins.rst

@@ -52,10 +52,12 @@ true the contents of the block are processed. Being true is defined as:
 
 .. code-block:: html+django
 
-    {% if variable %}
-      The variable was found in the current context.
+    {% if admin %}
+      The user is an administrator.
+    {% elif user %}
+      A user is logged in.
     {% else %}
-      The variable was not found.
+      No user was found.
     {% endif %}
 
 Operators