Merge pull request #761 from davidungar/relax-time-2

[Incremental] Relax the priors currency test by what ought to be enough to get through CI

Author: David Ungar

Sources/SwiftDriver/IncrementalCompilation/IncrementalDependencyAndInputSetup.swift

@@ -223,10 +223,12 @@ 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(priorsModTime: priorsModTime, buildRecordModTime: buildRecordModTime) {
+    catch let ModuleDependencyGraph.ReadError.timeTravellingPriors(priorsModTime: priorsModTime,
+                                                                   buildRecordModTime: buildRecordModTime,
+                                                                   priorsTimeIntervalSinceStart: priorsTimeIntervalSinceStart) {
       diagnosticEngine.emit(
         warning: "Will not do cross-module incremental builds, priors saved at \(priorsModTime)), " +
-        "but the previous build started at \(buildRecordModTime) [delta: \(priorsModTime.timeIntervalSince(buildRecordModTime))], at '\(dependencyGraphPath)'")
+        "but the previous build started at \(buildRecordModTime) [priorsTimeIntervalSinceStart: \(priorsTimeIntervalSinceStart)], at '\(dependencyGraphPath)'")
       graphIfPresent = nil
     }
     catch {

Sources/SwiftDriver/IncrementalCompilation/ModuleDependencyGraph.swift

@@ -587,7 +587,9 @@ extension ModuleDependencyGraph {
     case bogusNameOrContext
     case unknownKind
     case unknownDependencySourceExtension
-    case timeTravellingPriors(priorsModTime: Date, buildRecordModTime: Date)
+    case timeTravellingPriors(priorsModTime: Date,
+                              buildRecordModTime: Date,
+                              priorsTimeIntervalSinceStart: TimeInterval)
   }
 
   /// Attempts to read a serialized dependency graph from the given path.
@@ -815,8 +817,12 @@ extension ModuleDependencyGraph {
     else {
       return
     }
-    guard info.buildStartTime <= priorsModTime else {
-      throw ReadError.timeTravellingPriors(priorsModTime: priorsModTime, buildRecordModTime: buildRecordModTime)
+    let priorsTimeIntervalSinceStart = priorsModTime.timeIntervalSince(buildRecordModTime)
+    // CI seems to emit identical times; I'm not sure why. So compare to -1.
+    guard -1.0 < priorsTimeIntervalSinceStart else {
+      throw ReadError.timeTravellingPriors(priorsModTime: priorsModTime,
+                                           buildRecordModTime: buildRecordModTime,
+                                           priorsTimeIntervalSinceStart: priorsTimeIntervalSinceStart)
     }
   }
 }

Tests/SwiftDriverTests/IncrementalCompilationTests.swift

@@ -302,7 +302,7 @@ extension IncrementalCompilationTests {
   /// Ensure that a saved prior module dependency graph is rejected if not from the previous build
   func testObsoletePriors() throws {
 #if !os(Linux)
-    let before = Date()
+    let before = Date().advanced(by: -2.0)
     let driver = try buildInitialState(checkDiagnostics: true)
     let path = try XCTUnwrap(driver.buildRecordInfo?.dependencyGraphPath)
     try setModTime(of: path, to: before) // Make priors too old