Merge pull request swiftlang#758 from davidungar/stab-at-fixing-irreproducible-ci-failure

[Incremental] Relax currency test to fix ci errors

Author: David Ungar

Sources/SwiftDriver/IncrementalCompilation/IncrementalDependencyAndInputSetup.swift

@@ -186,10 +186,6 @@ extension IncrementalCompilationState {
         incrementalOptions: options, buildStartTime: buildStartTime,
         buildEndTime: buildEndTime)
     }
-
-    var buildTimeSpan: ClosedRange<Date> {
-      buildStartTime...buildEndTime
-    }
   }
 }
 
@@ -227,10 +223,10 @@ extension IncrementalCompilationState.IncrementalDependencyAndInputSetup {
         warning: "Will not do cross-module incremental builds, wrong version of priors; expected \(expected) but read \(read) at '\(dependencyGraphPath)'")
       graphIfPresent = nil
     }
-    catch let ModuleDependencyGraph.ReadError.timeTravellingPriors(priorsDate, timeSpan) {
+    catch let ModuleDependencyGraph.ReadError.timeTravellingPriors(priorsModTime: priorsModTime, buildRecordModTime: buildRecordModTime) {
       diagnosticEngine.emit(
-        warning: "Will not do cross-module incremental builds, priors saved at \(priorsDate), " +
-        "but the previous build happend from \(timeSpan.lowerBound) to \(timeSpan.upperBound), at '\(dependencyGraphPath)'")
+        warning: "Will not do cross-module incremental builds, priors saved at \(priorsModTime)), " +
+        "but the previous build started at \(buildRecordModTime), at '\(dependencyGraphPath)'")
       graphIfPresent = nil
     }
     catch {

Sources/SwiftDriver/IncrementalCompilation/ModuleDependencyGraph.swift

@@ -587,7 +587,7 @@ extension ModuleDependencyGraph {
     case bogusNameOrContext
     case unknownKind
     case unknownDependencySourceExtension
-    case timeTravellingPriors(Date, ClosedRange<Date>)
+    case timeTravellingPriors(priorsModTime: Date, buildRecordModTime: Date)
   }
 
   /// Attempts to read a serialized dependency graph from the given path.
@@ -809,13 +809,14 @@ extension ModuleDependencyGraph {
   fileprivate static func ensurePriorsCreatedDuringPriorBuild(
     at path: VirtualPath,
     info: IncrementalCompilationState.IncrementalDependencyAndInputSetup) throws {
-    guard let priorsModTime = try? info.fileSystem.lastModificationTime(for: path)
+    guard let priorsModTime = try? info.fileSystem.lastModificationTime(for: path),
+          let buildRecordModTime =
+            try? info.fileSystem.lastModificationTime(for: info.buildRecordInfo.buildRecordPath)
     else {
       return
     }
-    let priorBuildTimeSpan = info.buildTimeSpan
-    guard priorBuildTimeSpan.contains(priorsModTime) else {
-      throw ReadError.timeTravellingPriors(priorsModTime, priorBuildTimeSpan)
+    guard info.buildStartTime <= priorsModTime else {
+      throw ReadError.timeTravellingPriors(priorsModTime: priorsModTime, buildRecordModTime: buildRecordModTime)
     }
   }
 }

Tests/SwiftDriverTests/IncrementalCompilationTests.swift

@@ -836,7 +836,6 @@ extension IncrementalCompilationTests {
       else {
         let firstWave = haveGraph ? changedInputs : inputs
         let omittedFromFirstWave = haveGraph ? unchangedInputs : []
-        let forcedInFirstWave = haveGraph ? [] : inputs
         schedulingChanged(changedInputs)
         maySkip(unchangedInputs)
         queuingInitial(firstWave)