Errors logs improvements

CHANGELOG.md

@@ -12,8 +12,11 @@
   [David Jennes](https://github.com/djbe)
   [#215](https://github.com/stencilproject/Stencil/pull/215)
 - Adds support for using spaces in filter expression.  
-  [Ilya Puchka](https://github.com/yonaskolb)
+  [Ilya Puchka](https://github.com/ilyapuchka)
   [#178](https://github.com/stencilproject/Stencil/pull/178)
+- Improvements in error reporting.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#167](https://github.com/stencilproject/Stencil/pull/167)
 
 ### Bug Fixes
 

Sources/Context.swift

@@ -3,6 +3,10 @@ public class Context {
   var dictionaries: [[String: Any?]]
 
   public let environment: Environment
+
+  public var errorReporter: ErrorReporter {
+    return environment.errorReporter
+  }
 
   init(dictionary: [String: Any]? = nil, environment: Environment? = nil) {
     if let dictionary = dictionary {

Sources/Environment.swift

@@ -3,9 +3,15 @@ public struct Environment {
   public var extensions: [Extension]
 
   public var loader: Loader?
+  public var errorReporter: ErrorReporter
+
+  public init(loader: Loader? = nil,
+              extensions: [Extension]? = nil,
+              templateClass: Template.Type = Template.self,
+              errorReporter: ErrorReporter = SimpleErrorReporter()) {
 
-  public init(loader: Loader? = nil, extensions: [Extension]? = nil, templateClass: Template.Type = Template.self) {
     self.templateClass = templateClass
+    self.errorReporter = errorReporter
     self.loader = loader
     self.extensions = (extensions ?? []) + [DefaultExtension()]
   }
@@ -28,11 +34,18 @@ public struct Environment {
 
   public func renderTemplate(name: String, context: [String: Any]? = nil) throws -> String {
     let template = try loadTemplate(name: name)
-    return try template.render(context)
+    return try render(template: template, context: context)
   }
 
   public func renderTemplate(string: String, context: [String: Any]? = nil) throws -> String {
     let template = templateClass.init(templateString: string, environment: self)
+    return try render(template: template, context: context)
+  }
+
+  func render(template: Template, context: [String: Any]?) throws -> String {
+    // update template environment as it can be created from string literal with default environment
+    template.environment = self
     return try template.render(context)
   }
+
 }

Sources/Errors.swift

@@ -17,3 +17,67 @@ public class TemplateDoesNotExist: Error, CustomStringConvertible {
     return "Template named `\(templates)` does not exist. No loaders found"
   }
 }
+
+public struct TemplateSyntaxError : Error, Equatable, CustomStringConvertible {
+  public let reason: String
+  public var description: String { return reason }
+  public internal(set) var token: Token?
+  public internal(set) var stackTrace: [Token]
+  public var templateName: String? { return token?.sourceMap.filename }
+  var allTokens: [Token] {
+    return stackTrace + (token.map({ [$0] }) ?? [])
+  }
+
+  public init(reason: String, token: Token? = nil, stackTrace: [Token] = []) {
+    self.reason = reason
+    self.stackTrace = stackTrace
+    self.token = token
+  }
+
+  public init(_ description: String) {
+    self.init(reason: description)
+  }
+
+  public static func ==(lhs:TemplateSyntaxError, rhs:TemplateSyntaxError) -> Bool {
+    return lhs.description == rhs.description && lhs.token == rhs.token && lhs.stackTrace == rhs.stackTrace
+  }
+
+}
+
+extension Error {
+  func withToken(_ token: Token?) -> Error {
+    if var error = self as? TemplateSyntaxError {
+      error.token = error.token ?? token
+      return error
+    } else {
+      return TemplateSyntaxError(reason: "\(self)", token: token)
+    }
+  }
+}
+
+public protocol ErrorReporter: class {
+  func renderError(_ error: Error) -> String
+}
+
+open class SimpleErrorReporter: ErrorReporter {
+
+  open func renderError(_ error: Error) -> String {
+    guard let templateError = error as? TemplateSyntaxError else { return error.localizedDescription }
+
+    func describe(token: Token) -> String {
+      let templateName = token.sourceMap.filename ?? ""
+      let line = token.sourceMap.line
+      let highlight = "\(String(Array(repeating: " ", count: line.offset)))^\(String(Array(repeating: "~", count: max(token.contents.characters.count - 1, 0))))"
+
+      return "\(templateName)\(line.number):\(line.offset): error: \(templateError.reason)\n"
+        + "\(line.content)\n"
+        + "\(highlight)\n"
+    }
+
+    var descriptions = templateError.stackTrace.reduce([]) { $0 + [describe(token: $1)] }
+    let description = templateError.token.map(describe(token:)) ?? templateError.reason
+    descriptions.append(description)
+    return descriptions.joined(separator: "\n")
+  }
+
+}

Sources/Expression.swift

@@ -88,21 +88,21 @@ final class NotExpression: Expression, PrefixOperator, CustomStringConvertible {
 final class InExpression: Expression, InfixOperator, CustomStringConvertible {
   let lhs: Expression
   let rhs: Expression
-  
+
   init(lhs: Expression, rhs: Expression) {
     self.lhs = lhs
     self.rhs = rhs
   }
-  
+
   var description: String {
     return "(\(lhs) in \(rhs))"
   }
-  
+
   func evaluate(context: Context) throws -> Bool {
     if let lhs = lhs as? VariableExpression, let rhs = rhs as? VariableExpression {
       let lhsValue = try lhs.variable.resolve(context)
       let rhsValue = try rhs.variable.resolve(context)
-      
+
       if let lhs = lhsValue as? AnyHashable, let rhs = rhsValue as? [AnyHashable] {
         return rhs.contains(lhs)
       } else if let lhs = lhsValue as? Int, let rhs = rhsValue as? CountableClosedRange<Int> {
@@ -115,10 +115,10 @@ final class InExpression: Expression, InfixOperator, CustomStringConvertible {
         return true
       }
     }
-    
+
     return false
   }
-  
+
 }
 
 final class OrExpression: Expression, InfixOperator, CustomStringConvertible {

Sources/Extension.swift

@@ -15,7 +15,7 @@ open class Extension {
   /// Registers a simple template tag with a name and a handler
   public func registerSimpleTag(_ name: String, handler: @escaping (Context) throws -> String) {
     registerTag(name, parser: { parser, token in
-      return SimpleNode(handler: handler)
+      return SimpleNode(token: token, handler: handler)
     })
   }
 
@@ -42,9 +42,9 @@ class DefaultExtension: Extension {
     registerTag("for", parser: ForNode.parse)
     registerTag("if", parser: IfNode.parse)
     registerTag("ifnot", parser: IfNode.parse_ifnot)
-#if !os(Linux)
-    registerTag("now", parser: NowNode.parse)
-#endif
+    #if !os(Linux)
+      registerTag("now", parser: NowNode.parse)
+    #endif
     registerTag("include", parser: IncludeNode.parse)
     registerTag("extends", parser: ExtendsNode.parse)
     registerTag("block", parser: BlockNode.parse)

Sources/FilterTag.swift

@@ -1,6 +1,7 @@
 class FilterNode : NodeType {
   let resolvable: Resolvable
   let nodes: [NodeType]
+  let token: Token?
 
   class func parse(_ parser: TokenParser, token: Token) throws -> NodeType {
     let bits = token.components()
@@ -15,20 +16,21 @@ class FilterNode : NodeType {
       throw TemplateSyntaxError("`endfilter` was not found.")
     }
 
-    let resolvable = try parser.compileFilter("filter_value|\(bits[1])")
-    return FilterNode(nodes: blocks, resolvable: resolvable)
+    let resolvable = try parser.compileFilter("filter_value|\(bits[1])", containedIn: token)
+    return FilterNode(nodes: blocks, resolvable: resolvable, token: token)
   }
 
-  init(nodes: [NodeType], resolvable: Resolvable) {
+  init(nodes: [NodeType], resolvable: Resolvable, token: Token) {
     self.nodes = nodes
     self.resolvable = resolvable
+    self.token = token
   }
 
   func render(_ context: Context) throws -> String {
     let value = try renderNodes(nodes, context)
 
     return try context.push(dictionary: ["filter_value": value]) {
-      return try VariableNode(variable: resolvable).render(context)
+      return try VariableNode(variable: resolvable, token: token).render(context)
     }
   }
 }

Sources/ForTag.swift

@@ -6,54 +6,56 @@ class ForNode : NodeType {
   let nodes:[NodeType]
   let emptyNodes: [NodeType]
   let `where`: Expression?
+  let token: Token?
 
   class func parse(_ parser:TokenParser, token:Token) throws -> NodeType {
     let components = token.components()
 
     func hasToken(_ token: String, at index: Int) -> Bool {
       return components.count > (index + 1) && components[index] == token
     }
+
     func endsOrHasToken(_ token: String, at index: Int) -> Bool {
       return components.count == index || hasToken(token, at: index)
     }
 
     guard hasToken("in", at: 2) && endsOrHasToken("where", at: 4) else {
-      throw TemplateSyntaxError("'for' statements should use the syntax: `for <x> in <y> [where <condition>]")
+      throw TemplateSyntaxError("'for' statements should use the syntax: `for <x> in <y> [where <condition>]`.")
     }
 
     let loopVariables = components[1].characters
       .split(separator: ",")
       .map(String.init)
       .map { $0.trim(character: " ") }
 
-    var emptyNodes = [NodeType]()
+    let resolvable = try parser.compileResolvable(components[3], containedIn: token)
+
+    let `where` = hasToken("where", at: 4)
+      ? try parseExpression(components: Array(components.suffix(from: 5)), tokenParser: parser, token: token)
+      : nil
 
     let forNodes = try parser.parse(until(["endfor", "empty"]))
 
     guard let token = parser.nextToken() else {
       throw TemplateSyntaxError("`endfor` was not found.")
     }
 
+    var emptyNodes = [NodeType]()
     if token.contents == "empty" {
       emptyNodes = try parser.parse(until(["endfor"]))
       _ = parser.nextToken()
     }
 
-    let resolvable = try parser.compileResolvable(components[3])
-
-    let `where` = hasToken("where", at: 4)
-      ? try parseExpression(components: Array(components.suffix(from: 5)), tokenParser: parser)
-      : nil
-
-    return ForNode(resolvable: resolvable, loopVariables: loopVariables, nodes: forNodes, emptyNodes:emptyNodes, where: `where`)
+    return ForNode(resolvable: resolvable, loopVariables: loopVariables, nodes: forNodes, emptyNodes: emptyNodes, where: `where`, token: token)
   }
 
-  init(resolvable: Resolvable, loopVariables: [String], nodes:[NodeType], emptyNodes:[NodeType], where: Expression? = nil) {
+  init(resolvable: Resolvable, loopVariables: [String], nodes: [NodeType], emptyNodes: [NodeType], where: Expression? = nil, token: Token? = nil) {
     self.resolvable = resolvable
     self.loopVariables = loopVariables
     self.nodes = nodes
     self.emptyNodes = emptyNodes
     self.where = `where`
+    self.token = token
   }
 
   func push<Result>(value: Any, context: Context, closure: () throws -> (Result)) throws -> Result {
@@ -143,7 +145,7 @@ class ForNode : NodeType {
             try renderNodes(nodes, context)
           }
         }
-      }.joined(separator: "")
+        }.joined(separator: "")
     }
 
     return try context.push {