Added filter to apply dynamic filters

CHANGELOG.md

@@ -12,6 +12,8 @@
   [Ilya Puchka](https://github.com/yonaskolb)
   [#178](https://github.com/stencilproject/Stencil/pull/178)
 
+- Added support for dynamic filter using `filter` filter
+
 ### Bug Fixes
 
 - Fixed using quote as a filter parameter

Sources/Expression.swift

@@ -1,4 +1,4 @@
-protocol Expression: CustomStringConvertible {
+public protocol Expression: CustomStringConvertible {
   func evaluate(context: Context) throws -> Bool
 }
 

Sources/Extension.swift

@@ -26,6 +26,10 @@ open class Extension {
 
   /// Registers a template filter with the given name
   public func registerFilter(_ name: String, filter: @escaping (Any?, [Any?]) throws -> Any?) {
+    filters[name] = .arguments({ value, args, _ in try filter(value, args) })
+  }
+
+  public func registerFilter(_ name: String, filter: @escaping (Any?, [Any?], Context) throws -> Any?) {
     filters[name] = .arguments(filter)
   }
 }
@@ -59,28 +63,28 @@ class DefaultExtension: Extension {
     registerFilter("join", filter: joinFilter)
     registerFilter("split", filter: splitFilter)
     registerFilter("indent", filter: indentFilter)
+    registerFilter("filter", filter: filterFilter)
   }
 }
 
 
 protocol FilterType {
-  func invoke(value: Any?, arguments: [Any?]) throws -> Any?
+  func invoke(value: Any?, arguments: [Any?], context: Context) throws -> Any?
 }
 
 enum Filter: FilterType {
   case simple(((Any?) throws -> Any?))
-  case arguments(((Any?, [Any?]) throws -> Any?))
+  case arguments(((Any?, [Any?], Context) throws -> Any?))
 
-  func invoke(value: Any?, arguments: [Any?]) throws -> Any? {
+  func invoke(value: Any?, arguments: [Any?], context: Context) throws -> Any? {
     switch self {
     case let .simple(filter):
       if !arguments.isEmpty {
         throw TemplateSyntaxError("cannot invoke filter with an argument")
       }
-
       return try filter(value)
     case let .arguments(filter):
-      return try filter(value, arguments)
+      return try filter(value, arguments, context)
     }
   }
 }

Sources/Filters.swift

@@ -39,7 +39,7 @@ func defaultFilter(value: Any?, arguments: [Any?]) -> Any? {
 
 func joinFilter(value: Any?, arguments: [Any?]) throws -> Any? {
   guard arguments.count < 2 else {
-    throw TemplateSyntaxError("'join' filter takes a single argument")
+    throw TemplateSyntaxError("'join' filter takes at most one argument")
   }
 
   let separator = stringify(arguments.first ?? "")
@@ -55,7 +55,7 @@ func joinFilter(value: Any?, arguments: [Any?]) throws -> Any? {
 
 func splitFilter(value: Any?, arguments: [Any?]) throws -> Any? {
   guard arguments.count < 2 else {
-    throw TemplateSyntaxError("'split' filter takes a single argument")
+    throw TemplateSyntaxError("'split' filter takes at most one argument")
   }
 
   let separator = stringify(arguments.first ?? " ")
@@ -111,3 +111,16 @@ func indent(_ content: String, indentation: String, indentFirst: Bool) -> String
   return result.joined(separator: "\n")
 }
 
+func filterFilter(value: Any?, arguments: [Any?], context: Context) throws -> Any? {
+  guard let value = value else { return nil }
+  guard arguments.count == 1 else {
+    throw TemplateSyntaxError("'filter' filter takes one argument")
+  }
+
+  let attribute = stringify(arguments[0])
+
+  let expr = try context.environment.compileFilter("$0|\(attribute)")
+  return try context.push(dictionary: ["$0": value]) {
+    try expr.resolve(context)
+  }
+}

Sources/ForTag.swift

@@ -42,7 +42,7 @@ class ForNode : NodeType {
     let resolvable = try parser.compileResolvable(components[3])
 
     let `where` = hasToken("where", at: 4)
-      ? try parseExpression(components: Array(components.suffix(from: 5)), tokenParser: parser)
+      ? try parser.compileExpression(components: Array(components.suffix(from: 5)))
       : nil
 
     return ForNode(resolvable: resolvable, loopVariables: loopVariables, nodes: forNodes, emptyNodes:emptyNodes, where: `where`)

Sources/IfTag.swift

@@ -100,7 +100,7 @@ final class IfExpressionParser {
   let tokens: [IfToken]
   var position: Int = 0
 
-  init(components: [String], tokenParser: TokenParser) throws {
+  init(components: [String], environment: Environment) throws {
     self.tokens = try components.map { component in
       if let op = findOperator(name: component) {
         switch op {
@@ -111,7 +111,7 @@ final class IfExpressionParser {
         }
       }
 
-      return .variable(try tokenParser.compileResolvable(component))
+      return .variable(try environment.compileResolvable(component))
     }
   }
 
@@ -155,12 +155,6 @@ final class IfExpressionParser {
 }
 
 
-func parseExpression(components: [String], tokenParser: TokenParser) throws -> Expression {
-  let parser = try IfExpressionParser(components: components, tokenParser: tokenParser)
-  return try parser.parse()
-}
-
-
 /// Represents an if condition and the associated nodes when the condition
 /// evaluates
 final class IfCondition {
@@ -187,7 +181,7 @@ class IfNode : NodeType {
     var components = token.components()
     components.removeFirst()
 
-    let expression = try parseExpression(components: components, tokenParser: parser)
+    let expression = try parser.compileExpression(components: components)
     let nodes = try parser.parse(until(["endif", "elif", "else"]))
     var conditions: [IfCondition] = [
       IfCondition(expression: expression, nodes: nodes)
@@ -197,7 +191,7 @@ class IfNode : NodeType {
     while let current = token, current.contents.hasPrefix("elif") {
       var components = current.components()
       components.removeFirst()
-      let expression = try parseExpression(components: components, tokenParser: parser)
+      let expression = try parser.compileExpression(components: components)
 
       let nodes = try parser.parse(until(["endif", "elif", "else"]))
       token = parser.nextToken()
@@ -236,7 +230,7 @@ class IfNode : NodeType {
       _ = parser.nextToken()
     }
 
-    let expression = try parseExpression(components: components, tokenParser: parser)
+    let expression = try parser.compileExpression(components: components)
     return IfNode(conditions: [
       IfCondition(expression: expression, nodes: trueNodes),
       IfCondition(expression: nil, nodes: falseNodes),

Sources/Parser.swift

@@ -48,7 +48,7 @@ public class TokenParser {
         }
 
         if let tag = token.components().first {
-          let parser = try findTag(name: tag)
+          let parser = try environment.findTag(name: tag)
           nodes.append(try parser(self, token))
         }
       case .comment:
@@ -71,8 +71,24 @@ public class TokenParser {
     tokens.insert(token, at: 0)
   }
 
+  public func compileFilter(_ token: String) throws -> Resolvable {
+    return try environment.compileFilter(token)
+  }
+
+  public func compileExpression(components: [String]) throws -> Expression {
+    return try environment.compileExpression(components: components)
+  }
+
+  public func compileResolvable(_ token: String) throws -> Resolvable {
+    return try environment.compileResolvable(token)
+  }
+
+}
+
+extension Environment {
+
   func findTag(name: String) throws -> Extension.TagParser {
-    for ext in environment.extensions {
+    for ext in extensions {
       if let filter = ext.tags[name] {
         return filter
       }
@@ -82,7 +98,7 @@ public class TokenParser {
   }
 
   func findFilter(_ name: String) throws -> FilterType {
-    for ext in environment.extensions {
+    for ext in extensions {
       if let filter = ext.filters[name] {
         return filter
       }
@@ -97,7 +113,7 @@ public class TokenParser {
   }
 
   private func suggestedFilters(for name: String) -> [String] {
-    let allFilters = environment.extensions.flatMap({ $0.filters.keys })
+    let allFilters = extensions.flatMap({ $0.filters.keys })
 
     let filtersWithDistance = allFilters
                 .map({ (filterName: $0, distance: $0.levenshteinDistance(name)) })
@@ -111,11 +127,15 @@ public class TokenParser {
   }
 
   public func compileFilter(_ token: String) throws -> Resolvable {
-    return try FilterExpression(token: token, parser: self)
+    return try FilterExpression(token: token, environment: self)
+  }
+
+  public func compileExpression(components: [String]) throws -> Expression {
+    return try IfExpressionParser(components: components, environment: self).parse()
   }
 
   public func compileResolvable(_ token: String) throws -> Resolvable {
-    return try RangeVariable(token, parser: self)
+    return try RangeVariable(token, environment: self)
       ?? compileFilter(token)
   }
 

Sources/Variable.swift

@@ -8,8 +8,8 @@ class FilterExpression : Resolvable {
   let filters: [(FilterType, [Variable])]
   let variable: Variable
 
-  init(token: String, parser: TokenParser) throws {
-    let bits = token.characters.split(separator: "|").map({ String($0).trim(character: " ") })
+  init(token: String, environment: Environment) throws {
+    let bits = token.smartSplit(separator: "|").map({ String($0).trim(character: " ") })
     if bits.isEmpty {
       filters = []
       variable = Variable("")
@@ -22,7 +22,7 @@ class FilterExpression : Resolvable {
     do {
       filters = try filterBits.map {
         let (name, arguments) = parseFilterComponents(token: $0)
-        let filter = try parser.findFilter(name)
+        let filter = try environment.findFilter(name)
         return (filter, arguments)
       }
     } catch {
@@ -36,7 +36,7 @@ class FilterExpression : Resolvable {
 
     return try filters.reduce(result) { x, y in
       let arguments = try y.1.map { try $0.resolve(context) }
-      return try y.0.invoke(value: x, arguments: arguments)
+      return try y.0.invoke(value: x, arguments: arguments, context: context)
     }
   }
 }
@@ -138,14 +138,14 @@ public struct RangeVariable: Resolvable {
   public let from: Resolvable
   public let to: Resolvable
 
-  public init?(_ token: String, parser: TokenParser) throws {
+  public init?(_ token: String, environment: Environment) throws {
     let components = token.components(separatedBy: "...")
     guard components.count == 2 else {
       return nil
     }
 
-    self.from = try parser.compileFilter(components[0])
-    self.to = try parser.compileFilter(components[1])
+    self.from = try environment.compileFilter(components[0])
+    self.to = try environment.compileFilter(components[1])
   }
 
   public func resolve(_ context: Context) throws -> Any? {

Tests/StencilTests/ExpressionSpec.swift

@@ -105,19 +105,19 @@ func testExpressions() {
 
     $0.describe("expression parsing") {
       $0.it("can parse a variable expression") {
-        let expression = try parseExpression(components: ["value"], tokenParser: parser)
+        let expression = try parser.compileExpression(components: ["value"])
         try expect(expression.evaluate(context: Context())).to.beFalse()
         try expect(expression.evaluate(context: Context(dictionary: ["value": true]))).to.beTrue()
       }
 
       $0.it("can parse a not expression") {
-        let expression = try parseExpression(components: ["not", "value"], tokenParser: parser)
+        let expression = try parser.compileExpression(components: ["not", "value"])
         try expect(expression.evaluate(context: Context())).to.beTrue()
         try expect(expression.evaluate(context: Context(dictionary: ["value": true]))).to.beFalse()
       }
 
       $0.describe("and expression") {
-        let expression = try! parseExpression(components: ["lhs", "and", "rhs"], tokenParser: parser)
+        let expression = try! parser.compileExpression(components: ["lhs", "and", "rhs"])
 
         $0.it("evaluates to false with lhs false") {
           try expect(expression.evaluate(context: Context(dictionary: ["lhs": false, "rhs": true]))).to.beFalse()
@@ -137,7 +137,7 @@ func testExpressions() {
       }
 
       $0.describe("or expression") {
-        let expression = try! parseExpression(components: ["lhs", "or", "rhs"], tokenParser: parser)
+        let expression = try! parser.compileExpression(components: ["lhs", "or", "rhs"])
 
         $0.it("evaluates to true with lhs true") {
           try expect(expression.evaluate(context: Context(dictionary: ["lhs": true, "rhs": false]))).to.beTrue()
@@ -157,7 +157,7 @@ func testExpressions() {
       }
 
       $0.describe("equality expression") {
-        let expression = try! parseExpression(components: ["lhs", "==", "rhs"], tokenParser: parser)
+        let expression = try! parser.compileExpression(components: ["lhs", "==", "rhs"])
 
         $0.it("evaluates to true with equal lhs/rhs") {
           try expect(expression.evaluate(context: Context(dictionary: ["lhs": "a", "rhs": "a"]))).to.beTrue()
@@ -193,7 +193,7 @@ func testExpressions() {
       }
 
       $0.describe("inequality expression") {
-        let expression = try! parseExpression(components: ["lhs", "!=", "rhs"], tokenParser: parser)
+        let expression = try! parser.compileExpression(components: ["lhs", "!=", "rhs"])
 
         $0.it("evaluates to true with inequal lhs/rhs") {
           try expect(expression.evaluate(context: Context(dictionary: ["lhs": "a", "rhs": "b"]))).to.beTrue()
@@ -205,7 +205,7 @@ func testExpressions() {
       }
 
       $0.describe("more than expression") {
-        let expression = try! parseExpression(components: ["lhs", ">", "rhs"], tokenParser: parser)
+        let expression = try! parser.compileExpression(components: ["lhs", ">", "rhs"])
 
         $0.it("evaluates to true with lhs > rhs") {
           try expect(expression.evaluate(context: Context(dictionary: ["lhs": 5.0, "rhs": 4]))).to.beTrue()
@@ -217,7 +217,7 @@ func testExpressions() {
       }
 
       $0.describe("more than equal expression") {
-        let expression = try! parseExpression(components: ["lhs", ">=", "rhs"], tokenParser: parser)
+        let expression = try! parser.compileExpression(components: ["lhs", ">=", "rhs"])
 
         $0.it("evaluates to true with lhs == rhs") {
           try expect(expression.evaluate(context: Context(dictionary: ["lhs": 5.0, "rhs": 5]))).to.beTrue()
@@ -229,7 +229,7 @@ func testExpressions() {
       }
 
       $0.describe("less than expression") {
-        let expression = try! parseExpression(components: ["lhs", "<", "rhs"], tokenParser: parser)
+        let expression = try! parser.compileExpression(components: ["lhs", "<", "rhs"])
 
         $0.it("evaluates to true with lhs < rhs") {
           try expect(expression.evaluate(context: Context(dictionary: ["lhs": 4, "rhs": 4.5]))).to.beTrue()
@@ -241,7 +241,7 @@ func testExpressions() {
       }
 
       $0.describe("less than equal expression") {
-        let expression = try! parseExpression(components: ["lhs", "<=", "rhs"], tokenParser: parser)
+        let expression = try! parser.compileExpression(components: ["lhs", "<=", "rhs"])
 
         $0.it("evaluates to true with lhs == rhs") {
           try expect(expression.evaluate(context: Context(dictionary: ["lhs": 5.0, "rhs": 5]))).to.beTrue()
@@ -253,7 +253,7 @@ func testExpressions() {
       }
 
       $0.describe("multiple expression") {
-        let expression = try! parseExpression(components: ["one", "or", "two", "and", "not", "three"], tokenParser: parser)
+        let expression = try! parser.compileExpression(components: ["one", "or", "two", "and", "not", "three"])
 
         $0.it("evaluates to true with one") {
           try expect(expression.evaluate(context: Context(dictionary: ["one": true]))).to.beTrue()
@@ -281,7 +281,7 @@ func testExpressions() {
       }
 
       $0.describe("in expression") {
-        let expression = try! parseExpression(components: ["lhs", "in", "rhs"], tokenParser: parser)
+        let expression = try! parser.compileExpression(components: ["lhs", "in", "rhs"])
 
         $0.it("evaluates to true when rhs contains lhs") {
           try expect(expression.evaluate(context: Context(dictionary: ["lhs": 1, "rhs": [1, 2, 3]]))).to.beTrue()