Merge pull request #467 from CodaFi/reader-writer-locks

Author: CodaFi

Sources/SwiftDriver/Driver/Driver.swift

@@ -201,6 +201,22 @@ public struct Driver {
   /// Only used for reading when compiling incrementally.
   let buildRecordInfo: BuildRecordInfo?
 
+  /// A build-record-relative path to the location of a serialized copy of the
+  /// driver's dependency graph.
+  ///
+  /// FIXME: This is a little ridiculous. We could probably just replace the
+  /// build record outright with a serialized format.
+  var driverDependencyGraphPath: VirtualPath? {
+    guard let recordInfo = self.buildRecordInfo else {
+      return nil
+    }
+    let filename = recordInfo.buildRecordPath.basenameWithoutExt
+    return recordInfo
+      .buildRecordPath
+      .parentDirectory
+      .appending(component: filename + ".priors")
+  }
+  
   /// Code & data for incremental compilation. Nil if not running in incremental mode.
   /// Set during planning because needs the jobs to look at outputs.
   @_spi(Testing) public private(set) var incrementalCompilationState: IncrementalCompilationState? = nil
@@ -910,6 +926,7 @@ extension Driver {
     if !childJobs.isEmpty {
       do {
         defer {
+          self.incrementalCompilationState?.writeDependencyGraph()
           buildRecordInfo?.writeBuildRecord(
             jobs,
             incrementalCompilationState?.skippedCompilationInputs)

Sources/SwiftDriver/IncrementalCompilation/BuildRecordInfo.swift

@@ -18,7 +18,7 @@ import SwiftOptions
 /// compilation record).
 ///
 /// This info is always written, but only read for incremental compilation.
-final class BuildRecordInfo {
+@_spi(Testing) public final class BuildRecordInfo {
   /// A pair of a `Job` and the `ProcessResult` corresponding to the outcome of
   /// its execution during this compilation session.
   struct JobResult {
@@ -122,16 +122,19 @@ final class BuildRecordInfo {
   }
 
   /// Write out the build record.
-  /// `Jobs` must include all of the compilation jobs.
-  /// `Inputs` will hold all the primary inputs that were not compiled because of incremental compilation
-  func writeBuildRecord(_ jobs: [Job], _ skippedInputs: Set<TypedVirtualPath>? ) {
+  ///
+  /// - Parameters:
+  ///   - jobs: All compilation jobs formed during this build.
+  ///   - skippedInputs: All primary inputs that were not compiled because the
+  ///                    incremental build plan determined they could be
+  ///                    skipped.
+  func writeBuildRecord(_ jobs: [Job], _ skippedInputs: Set<TypedVirtualPath>?) {
     guard let absPath = buildRecordPath.absolutePath else {
       diagnosticEngine.emit(
         .warning_could_not_write_build_record_not_absolutePath(buildRecordPath))
       return
     }
     preservePreviousBuildRecord(absPath)
-    
 
     let buildRecord = self.confinementQueue.sync {
       BuildRecord(
@@ -155,7 +158,7 @@ final class BuildRecordInfo {
     } catch {
       diagnosticEngine.emit(.warning_could_not_write_build_record(absPath))
     }
- }
+  }
 
   /// Before writing to the dependencies file path, preserve any previous file
   /// that may have been there. No error handling -- this is just a nicety, it