Error handling

Author: swhitty

CommandLine/CommandLine.swift

@@ -42,14 +42,19 @@ extension SwiftDraw.CommandLine {
             printHelp()
             return .error
         }
-        
-        guard
-            let data = try? process(with: config) else {
-            print("Failure", to: &.standardError)
+
+        let data: Data
+        do {
+            data = try process(with: config)
+        } catch Error.fileNotFound {
+            print("Failure: File does not exist.", to: &.standardError)
+            return .error
+        } catch {
+            print("Failure:", error.localizedDescription, to: &.standardError)
             printHelp()
             return .error
         }
-        
+
         do {
             try data.write(to: config.output)
             print("Created: \(config.output.path)")
@@ -61,24 +66,32 @@ extension SwiftDraw.CommandLine {
     }
 
     static func process(with config: Configuration) throws -> Data {
-        guard let data = processImage(config: config) else {
+        guard let data = try processImage(config: config) else {
             throw Error.invalid
         }
 
         return data
     }
 
-    static func processImage(config: Configuration) -> Data? {
+    static func processImage(config: Configuration) throws -> Data? {
+        guard FileManager.default.fileExists(atPath: config.input.path) else {
+            throw Error.fileNotFound
+        }
+
         switch config.format {
         case .swift:
-            let code = CGTextRenderer.render(fileURL: config.input, size: config.size.renderSize, options: config.options)
-            return code?.data(using: .utf8)
+            let code = try CGTextRenderer.render(fileURL: config.input, size: config.size.renderSize, options: config.options)
+            return code.data(using: .utf8)
         case .sfsymbol:
             print("[--format sfsymbol] is an experimental feature.")
-            let svg = try? SFSymbolRenderer.render(fileURL: config.input, options: config.options)
-            return svg?.data(using: .utf8)
+            let svg = try SFSymbolRenderer.render(fileURL: config.input, options: config.options)
+            return svg.data(using: .utf8)
         case .jpeg, .pdf, .png:
-            return SwiftDraw.Image(fileURL: config.input, options: config.options).flatMap { processImage($0, with: config) }
+            guard let image = SwiftDraw.Image(fileURL: config.input, options: config.options),
+                  let data = processImage(image, with: config) else {
+                throw Error.invalid
+            }
+            return data
         }
     }
 

SwiftDraw/CGTextRenderer+Code.swift

@@ -35,18 +35,16 @@ public extension CGTextRenderer {
 
     typealias Size = (width: Int, height: Int)
 
-    static func render(named name: String, in bundle: Bundle = Bundle.main, size: Size? = nil, options: Image.Options) -> String? {
-        guard let url = bundle.url(forResource: name, withExtension: nil) else { return nil }
-        return render(fileURL: url, size: size, options: options)
-    }
-
-    static func render(fileURL: URL, size: Size? = nil, options: Image.Options) -> String? {
-        guard let svg = try? DOM.SVG.parse(fileURL: fileURL) else {
-            return nil
+    static func render(named name: String, in bundle: Bundle = Bundle.main, size: Size? = nil, options: Image.Options) throws -> String {
+        guard let url = bundle.url(forResource: name, withExtension: nil) else {
+            throw Error("File not found.")
         }
+        return try render(fileURL: url, size: size, options: options)
+    }
 
+    static func render(fileURL: URL, size: Size? = nil, options: Image.Options) throws -> String {
+        let svg = try DOM.SVG.parse(fileURL: fileURL)
         let size = makeSize(svg: svg, size: size)
-
         let identifier = fileURL.lastPathComponent
             .replacingOccurrences(of: ".\(fileURL.pathExtension)", with: "")
             .replacingOccurrences(of: "_", with: " ")
@@ -93,4 +91,12 @@ public extension CGTextRenderer {
 
         return renderer.makeText()
     }
+
+    private struct Error: LocalizedError {
+        var errorDescription: String?
+
+        init(_ message: String) {
+            self.errorDescription = message
+        }
+    }
 }

SwiftDraw/CommandLine.Arguments.swift

@@ -65,6 +65,7 @@ extension CommandLine {
 
     public enum Error: Swift.Error {
         case invalid
+        case fileNotFound
     }
 }
 

SwiftDraw/Renderer.SFSymbol.swift

@@ -35,17 +35,6 @@ public final class SFSymbolRenderer { }
 
 extension SFSymbolRenderer {
 
-    func makeDOM(for layer: LayerTree.Layer) throws -> DOM.SVG {
-        throw Error.invalid
-    }
-
-    static func firstPath(for layer: LayerTree.Layer) throws -> LayerTree.Path {
-        guard let path = getPaths(for: layer).first else {
-            throw Error.invalid
-        }
-        return path
-    }
-
     static func getPaths(for layer: LayerTree.Layer) -> [LayerTree.Path] {
         guard layer.opacity > 0,
               layer.clip.isEmpty,
@@ -78,11 +67,14 @@ extension SFSymbolRenderer {
                          fill: LayerTree.FillAttributes) -> LayerTree.Path? {
         guard case .path(let p) = shape else { return nil }
 
-        #if canImport(CoreGraphics)
         if stoke.color != .none && stoke.width > 0 {
+        #if canImport(CoreGraphics)
             return expandOutlines(for: p, stroke: stoke)
-        }
+        #else
+            print("Warning:", "expanding stroke outlines requires macOS.", to: &.standardError)
+            return nil
         #endif
+        }
 
         if fill.fill != .none && fill.opacity > 0 {
             return p
@@ -149,8 +141,12 @@ extension SFSymbolRenderer {
         return dom
     }
 
-    enum Error: Swift.Error {
-        case invalid
+    struct Error: LocalizedError {
+        var errorDescription: String?
+
+        init(_ message: String) {
+            self.errorDescription = message
+        }
     }
 }
 
@@ -167,6 +163,9 @@ public extension SFSymbolRenderer {
         let black = try svg.group(id: "Symbols").group(id: "Black-S")
 
         let sourcePaths = getPaths(for: layer)
+        guard !sourcePaths.isEmpty else {
+            throw Error("No valid content found.")
+        }
         regular.childElements.append(
             contentsOf: convertPaths(sourcePaths, into: .regular)
         )