remove priors

Author: David Ungar

Sources/SwiftDriver/IncrementalCompilation/IncrementalCompilationState.swift

@@ -500,6 +500,7 @@ extension IncrementalCompilationState {
       }
     }
   }
+
   @_spi(Testing) public func writeDependencyGraph() throws {
     // If the cross-module build is not enabled, the status quo dictates we
     // not emit this file.
@@ -515,6 +516,12 @@ extension IncrementalCompilationState {
                                          on: self.driver.fileSystem,
                                          compilerVersion: recordInfo.actualSwiftVersion)
   }
+
+  @_spi(Testing) public static func removeDependencyGraphFile(_ driver: Driver) {
+    if let path = driver.buildRecordInfo?.dependencyGraphPath {
+      try? driver.fileSystem.removeFileTree(path)
+    }
+  }
 }
 
 // MARK: - OutputFileMap

Sources/SwiftDriver/IncrementalCompilation/IncrementalDependencyAndInputSetup.swift

@@ -59,6 +59,7 @@ extension IncrementalCompilationState {
           driver.diagnosticEngine
         ).compute()
     else {
+      Self.removeDependencyGraphFile(driver)
       return nil
     }
 

Sources/SwiftDriver/Utilities/VirtualPath.swift

@@ -707,6 +707,12 @@ extension TSCBasic.FileSystem {
     }
   }
 
+  func removeFileTree(_ path: VirtualPath) throws {
+    try resolvingVirtualPath(path) { absolutePath in
+      try self.removeFileTree(absolutePath)
+    }
+  }
+
   func getFileInfo(_ path: VirtualPath) throws -> TSCBasic.FileInfo {
     try resolvingVirtualPath(path, apply: getFileInfo)
   }