Make parsing noise resilient

Author: finestructure

Sources/ReleaseNotesCore/Parser.swift

@@ -18,17 +18,11 @@ import SemanticVersion
 
 enum Parser {
 
-    static let progress = Skip(
-        "Updating"
-            .orElse("Updated")
-            .orElse("Computing")
-            .orElse("Computed")
-            .orElse("Creating working copy")
-            .orElse("Working copy of")
-    )
-        .skip(Prefix { $0 != "\n"})
-
-    static let anyProgress = Many(progress, separator: "\n")
+    static let dependencyStart = Int.parser().skip(" dependenc")
+    
+    static let progressLine = Not(dependencyStart).skip(PrefixThrough("\n"))
+
+    static let progress = Many(progressLine)
 
     static let dependencyCount = Int.parser()
         .skip(
@@ -73,13 +67,29 @@ enum Parser {
 
     static let updates = Many(update, separator: "\n")
 
-    static let packageUpdate = Skip(anyProgress)
+    static let packageUpdate = Skip(progress)
         .skip(Many("\n"))
         .take(dependencyCount)
         .take(updates)
         .map { (count, updates) -> [Update] in
             assert(updates.count == count)
             return updates
         }
-    
+
+}
+
+
+struct Not<P>: Parsing.Parser where P: Parsing.Parser {
+    let parser: P
+
+    init(_ parser: P) { self.parser = parser }
+
+    func parse(_ input: inout P.Input) -> Void? {
+        let original = input
+        if parser.parse(&input) != nil {
+          input = original
+          return nil
+        }
+        return ()
+    }
 }

Tests/ReleaseNotesTests/ParserCoreTests.swift

@@ -14,39 +14,40 @@
 
 @testable import ReleaseNotesCore
 import XCTest
+import Parsing
 
 
 final class ParserCoreTests: XCTestCase {
 
-    func test_progress() throws {
+    func test_progressLine() throws {
         do {
-            var input = "Updating https://github.com/pointfreeco/swift-parsing"[...]
-            XCTAssertNotNil(Parser.progress.parse(&input))
+            var input = "Updating https://github.com/pointfreeco/swift-parsing\n"[...]
+            XCTAssertNotNil(Parser.progressLine.parse(&input))
             XCTAssertEqual(input, "")
         }
         do {
-            var input = "Updated https://github.com/apple/swift-argument-parser (0.81s)"[...]
-            XCTAssertNotNil(Parser.progress.parse(&input))
+            var input = "Updated https://github.com/apple/swift-argument-parser (0.81s)\n"[...]
+            XCTAssertNotNil(Parser.progressLine.parse(&input))
             XCTAssertEqual(input, "")
         }
         do {
-            var input = "Computing version for https://github.com/pointfreeco/swift-parsing"[...]
-            XCTAssertNotNil(Parser.progress.parse(&input))
+            var input = "Computing version for https://github.com/pointfreeco/swift-parsing\n"[...]
+            XCTAssertNotNil(Parser.progressLine.parse(&input))
             XCTAssertEqual(input, "")
         }
         do {
-            var input = "Computed https://github.com/pointfreeco/swift-parsing at 0.4.1 (0.02s)"[...]
-            XCTAssertNotNil(Parser.progress.parse(&input))
+            var input = "Computed https://github.com/pointfreeco/swift-parsing at 0.4.1 (0.02s)\n"[...]
+            XCTAssertNotNil(Parser.progressLine.parse(&input))
             XCTAssertEqual(input, "")
         }
         do {
-            var input = "Creating working copy for https://github.com/JohnSundell/Plot.git"[...]
-            XCTAssertNotNil(Parser.progress.parse(&input))
+            var input = "Creating working copy for https://github.com/JohnSundell/Plot.git\n"[...]
+            XCTAssertNotNil(Parser.progressLine.parse(&input))
             XCTAssertEqual(input, "")
         }
         do {
-            var input = "Working copy of https://github.com/JohnSundell/Plot.git resolved at 0.10.0"[...]
-            XCTAssertNotNil(Parser.progress.parse(&input))
+            var input = "Working copy of https://github.com/JohnSundell/Plot.git resolved at 0.10.0\n"[...]
+            XCTAssertNotNil(Parser.progressLine.parse(&input))
             XCTAssertEqual(input, "")
         }
     }
@@ -67,8 +68,9 @@ final class ParserCoreTests: XCTestCase {
             Computed https://github.com/apple/swift-argument-parser at 1.0.2 (0.01s)
             Creating working copy for https://github.com/JohnSundell/Plot.git
             Working copy of https://github.com/JohnSundell/Plot.git resolved at 0.10.0
+
             """[...]
-        XCTAssertNotNil(Parser.anyProgress.parse(&input))
+        XCTAssertNotNil(Skip(Parser.progress).parse(&input))
         XCTAssertEqual(input, "")
     }
 
@@ -300,4 +302,16 @@ final class ParserCoreTests: XCTestCase {
         XCTAssertEqual(Parser.packageUpdate.parse(&input)?.count, 6)
     }
 
+    func test_progress_resilience() throws {
+        // Ensure random output before the dependency count line is ignored
+        var input = """
+            foo
+            bar
+            ~ something
+            1 dependency has changed:
+            ~ fluent-postgres-driver 2.2.2 -> fluent-postgres-driver 2.2.3
+            """[...]
+        XCTAssertEqual(Parser.packageUpdate.parse(&input)?.count, 1)
+    }
+
 }