Remove Package.resolved and move to depending on HEAD

.gitignore

@@ -1,5 +1,6 @@
 .DS_Store
 default.profraw
+Package.resolved
 /.build
 /Packages
 /*.xcodeproj

Package.swift

@@ -7,8 +7,7 @@ let package = Package(
     products: [
     ],
     dependencies: [
-      .package(url: "https://github.com/apple/swift-package-manager.git", .branch("master")),
-      .package(url: "https://github.com/apple/indexstore-db.git", .branch("master")),
+      // See 'Dependencies' below.
     ],
     targets: [
       .target(
@@ -82,3 +81,28 @@ let package = Package(
         dependencies: ["SKSupport", "SKTestSupport"]),
     ]
 )
+
+// MARK: Dependencies
+
+// When building with the swift build-script, use local dependencies whose contents are controlled
+// by the external environment. This allows sourcekit-lsp to take advantage of the automation used
+// for building the swift toolchain, such as `update-checkout`, or cross-repo PR tests.
+
+#if os(Linux)
+import Glibc
+#else
+import Darwin.C
+#endif
+
+if getenv("SWIFTCI_USE_LOCAL_DEPS") == nil {
+  // Building standalone.
+  package.dependencies += [
+    .package(url: "https://github.com/apple/indexstore-db.git", .branch("master")),
+    .package(url: "https://github.com/apple/swift-package-manager.git", .branch("master")),
+  ]
+} else {
+  package.dependencies += [
+    .package(path: "../indexstore-db"),
+    .package(path: "../swiftpm"),
+  ]
+}

README.md

@@ -7,7 +7,7 @@ SourceKit-LSP is an implementation of the [Language Server Protocol](https://mic
 
 SourceKit-LSP is under heavy development! The best way to try it out is to build it from source. You will also need a Swift development toolchain and an editor that supports LSP.
 
-1. Install the `swift-DEVELOPMENT-SNAPSHOT-2019-02-14-a` toolchain snapshot from https://swift.org/download/#snapshots. Set the environment variable `SOURCEKIT_TOOLCHAIN_PATH` to the absolute path to the toolchain or otherwise configure your editor to use this toolchain. See [Toolchains](#toolchains) for more information.
+1. Install the latest master toolchain snapshot from https://swift.org/download/#snapshots. Set the environment variable `SOURCEKIT_TOOLCHAIN_PATH` to the absolute path to the toolchain or otherwise configure your editor to use this toolchain. See [Toolchains](#toolchains) for more information.
 
 2. Build the language server executable `sourcekit-lsp` using `swift build`. See [Building](#building-sourcekit-lsp) for more information.
 
@@ -23,11 +23,14 @@ SourceKit-LSP is built using the [Swift Package Manager](https://github.com/appl
 For a standard debug build:
 
 ```sh
+$ swift package update
 $ swift build
 ```
 
 After building, the server will be located at `.build/debug/sourcekit-lsp`, or a similar path, if you passed any custom options to `swift build`. Editors will generally need to be provided with this path in order to run the newly built server - see [Editors](Editors) for more information about configuration.
 
+SourceKit-LSP is designed to build against the latest SwiftPM, so if you run into any issue make sure you have the most up-to-date dependencies by running `swift package update`.
+
 ### Building on Linux
 
 The C++ code in the index requires `libdispatch`, but unlike Swift code, it cannot find it automatically on Linux. You can work around this by adding a search path manually.
@@ -73,7 +76,7 @@ SourceKit-LSP depends on tools such as `sourcekitd` and `clangd`, which it loads
 
 ### Recommended Toolchain
 
-Use the `swift-DEVELOPMENT-SNAPSHOT-2019-02-14-a` toolchain snapshot from https://swift.org/download/#snapshots. SourceKit-LSP is still early in its development and we are actively adding functionality to the toolchain to support it.
+Use the latest master toolchain snapshot from https://swift.org/download/#snapshots. SourceKit-LSP is still early in its development and we are actively adding functionality to the toolchain to support it.
 
 ### Selecting the Toolchain
 

Utilities/build-script-helper.py

@@ -66,15 +66,18 @@ def add_common_args(parser):
 
   swiftpm_args = get_swiftpm_options(args)
 
+  env = os.environ
+  # Set the toolchain used in tests at runtime
+  env['SOURCEKIT_TOOLCHAIN_PATH'] = args.toolchain
+  # Use local dependencies (i.e. checked out next sourcekit-lsp).
+  env['SWIFTCI_USE_LOCAL_DEPS'] = "1"
+
   if args.action == 'build':
-    swiftpm('build', swift_exec, swiftpm_args)
+    swiftpm('build', swift_exec, swiftpm_args, env)
   elif args.action == 'test':
-    # Set the toolchain used in tests at runtime
-    env = os.environ
-    env['SOURCEKIT_TOOLCHAIN_PATH'] = args.toolchain
     swiftpm('test', swift_exec, swiftpm_args, env)
   else:
     assert False, 'unknown action \'{}\''.format(args.action)
 
 if __name__ == '__main__':
-  main()
+  main()