[Fuchsia] Clean up path usage in GN templates

- Paths intererpreted by GN such as paths in inputs, sources, lib_dirs,
  etc should either be relative to BUILD.gn, or GN-absolute (relative to
  source root and start with "//").

  They should not be rebased as system-absolute paths; those are only
  needed for paths that are actually outside the source tree.

  If paths are used in multiple contexts, rebasing should be deferred
  until they are used in a context where rebased paths are required.

- Paths passed as arguments to scripts should be rebased on
  root_build_dir, which is the current working directory of the build.

  They should not be rebased on root_out_dir, as that is only the current
  working directory for the default toolchain. Using root_out_dir in
  place of root_build_dir breaks cross compilation.

  They should also not be resolved to system-absolute paths, as that
  introduces an undesired dependency on the location of the source tree.

- The 3rd argument to rebase_path has no effect for GN-absolute paths,
  which includes all paths built by appending to predefined variables
  such as root_out_dir.

Change-Id: I54ff2d9fed0daadacf5bd1bd8fdadc561c3a2882
Reviewed-on: https://chromium-review.googlesource.com/c/1448694
Commit-Queue: Michael Spang <spang@chromium.org>
Reviewed-by: Kevin Marshall <kmarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#629579}

build/config/fuchsia/BUILD.gn

@@ -10,7 +10,7 @@ assert(is_fuchsia)
 assert(!is_posix)
 
 config("compiler") {
-  sdk_version_file = rebase_path("${fuchsia_sdk}/.hash")
+  sdk_version_file = "${fuchsia_sdk}/.hash"
   sdk_version = read_file(sdk_version_file, "trim string")
   defines = [
     # To force full builds after SDK updates in case of ABI changes.
@@ -47,7 +47,7 @@ config("compiler") {
   ]
 
   # Add SDK lib dir for -lfdio above.
-  lib_dirs = [ rebase_path("${fuchsia_sdk}/arch/${current_cpu}/lib") ]
+  lib_dirs = [ "${fuchsia_sdk}/arch/${current_cpu}/lib" ]
 
   # TODO(crbug.com/821951): Clang enables SafeStack by default when targeting
   # Fuchsia, but it breaks some tests, notably in V8.
@@ -77,9 +77,9 @@ action("blobstore_extended_fvm") {
   ]
 
   args = [
-    rebase_path("${fuchsia_sdk}/tools/fvm"),
-    rebase_path("${_target_dir}/fvm.blk"),
-    rebase_path(blobstore_extended_path),
+    rebase_path("${fuchsia_sdk}/tools/fvm", root_build_dir),
+    rebase_path("${_target_dir}/fvm.blk", root_build_dir),
+    rebase_path(blobstore_extended_path, root_build_dir),
     _extend_size,
   ]
 }
@@ -117,8 +117,8 @@ action("blobstore_extended_qcow2") {
     "-O",
     "qcow2",
     "-c",
-    rebase_path(blobstore_extended_path),
-    rebase_path(blobstore_qcow_path),
+    rebase_path(blobstore_extended_path, root_build_dir),
+    rebase_path(blobstore_qcow_path, root_build_dir),
   ]
 }
 

build/config/fuchsia/fidl_library.gni

@@ -134,7 +134,7 @@ template("fidl_library") {
 
     inputs = [
       # Depend on the SDK hash, to ensure rebuild if the SDK tools change.
-      rebase_path("$fuchsia_sdk/.hash"),
+      "${fuchsia_sdk}/.hash",
       _response_file,
     ]
 
@@ -161,7 +161,7 @@ template("fidl_library") {
 
       inputs = [
         # Depend on the SDK hash, to ensure rebuild if the SDK tools change.
-        rebase_path("$fuchsia_sdk/.hash"),
+        "${fuchsia_sdk}/.hash",
         _json_representation,
       ]
 
@@ -177,11 +177,11 @@ template("fidl_library") {
         "-generators",
         "cpp",
         "-json",
-        rebase_path(_json_representation),
+        rebase_path(_json_representation, root_build_dir),
         "-include-base",
-        rebase_path(_output_gen_dir),
+        rebase_path(_output_gen_dir, root_build_dir),
         "-output-base",
-        rebase_path("${_output_base}"),
+        rebase_path("${_output_base}", root_build_dir),
       ]
     }
   }
@@ -198,7 +198,7 @@ template("fidl_library") {
 
       inputs = [
         # Depend on the SDK hash, to ensure rebuild if the SDK tools change.
-        rebase_path("$fuchsia_sdk/.hash"),
+        "${fuchsia_sdk}/.hash",
         _json_representation,
         "//build/fuchsia/fidlgen_js/fidl.py",  # The schema helper file.
       ]
@@ -210,14 +210,14 @@ template("fidl_library") {
       script = "//build/fuchsia/fidlgen_js/gen.py"
 
       args = [
-        rebase_path(_json_representation),
+        rebase_path(_json_representation, root_build_dir),
         "--output",
-        rebase_path("${_output_js_path}"),
+        rebase_path("${_output_js_path}", root_build_dir),
       ]
 
       data = []
       foreach(o, outputs) {
-        data += [ rebase_path(o) ]
+        data += [ o ]
       }
     }
   }

build/config/fuchsia/package.gni

@@ -35,7 +35,7 @@ template("fuchsia_package") {
 
   _pm_tool_path = "${fuchsia_sdk}/tools/pm"
 
-  _pkg_out_dir = "$root_out_dir/gen/" + get_label_info(pkg.package_name, "dir")
+  _pkg_out_dir = "${target_gen_dir}/${pkg.package_name}"
   _runtime_deps_file = "$_pkg_out_dir/${pkg.package_name}.runtime_deps"
   _archive_manifest = "$_pkg_out_dir/${pkg.package_name}.archive_manifest"
   _component_manifest = "$_pkg_out_dir/${pkg.package_name}.cmx"
@@ -122,7 +122,7 @@ template("fuchsia_package") {
 
     inputs = [
       # Depend on the SDK hash, to ensure rebuild if the SDK tools change.
-      rebase_path("$fuchsia_sdk/.hash"),
+      "${fuchsia_sdk}/.hash",
     ]
 
     outputs = [
@@ -132,7 +132,7 @@ template("fuchsia_package") {
     args = [
       rebase_path(_pm_tool_path, root_build_dir),
       "-k",
-      rebase_path(_key_file),
+      rebase_path(_key_file, root_build_dir),
       "genkey",
     ]
   }
@@ -150,7 +150,7 @@ template("fuchsia_package") {
 
     inputs = [
       # Depend on the SDK hash, to ensure rebuild if the SDK tools change.
-      rebase_path("$fuchsia_sdk/.hash"),
+      "${fuchsia_sdk}/.hash",
       _key_file,
     ]
 
@@ -161,11 +161,11 @@ template("fuchsia_package") {
     args = [
       rebase_path(_pm_tool_path, root_build_dir),
       "-o",
-      rebase_path(_pkg_out_dir),
+      rebase_path(_pkg_out_dir, root_build_dir),
       "-k",
-      rebase_path(_key_file),
+      rebase_path(_key_file, root_build_dir),
       "-m",
-      rebase_path(_archive_manifest),
+      rebase_path(_archive_manifest, root_build_dir),
       "build",
     ]
   }
@@ -183,7 +183,7 @@ template("fuchsia_package") {
 
     inputs = [
       # Depend on the SDK hash, to ensure rebuild if the SDK tools change.
-      rebase_path("$fuchsia_sdk/.hash"),
+      "${fuchsia_sdk}/.hash",
       _meta_far_file,
       _archive_manifest,
     ]
@@ -195,9 +195,9 @@ template("fuchsia_package") {
     args = [
       rebase_path(_pm_tool_path, root_build_dir),
       "-o",
-      rebase_path(_pkg_out_dir),
+      rebase_path(_pkg_out_dir, root_build_dir),
       "-m",
-      rebase_path(_archive_manifest),
+      rebase_path(_archive_manifest, root_build_dir),
       "archive",
     ]
   }

build/config/fuchsia/rules.gni

@@ -97,7 +97,7 @@ template("fuchsia_package_runner") {
       # Arguments used at build time by the runner script generator.
       args = [
         "--script-output-path",
-        rebase_path(script_path, root_build_dir, root_out_dir),
+        rebase_path(script_path, root_build_dir),
       ]
 
       if (defined(invoker.use_test_server) && invoker.use_test_server) {
@@ -108,11 +108,11 @@ template("fuchsia_package_runner") {
         foreach(cur_package, invoker.package_deps) {
           deps += [ cur_package[0] ]
           dep_package_path =
-              "$root_out_dir/gen/" + get_label_info(cur_package[0], "dir") +
-              "/" + cur_package[1] + "/" + cur_package[1] + ".far"
+              get_label_info(cur_package[0], "target_gen_dir") + "/" +
+              cur_package[1] + "/" + cur_package[1] + ".far"
           args += [
             "--package-dep",
-            rebase_path(dep_package_path, root_out_dir, root_build_dir),
+            rebase_path(dep_package_path, root_build_dir),
           ]
         }
       }
@@ -120,17 +120,17 @@ template("fuchsia_package_runner") {
       # Arguments used at runtime by the test runner.
       args += [
         "--runner-script",
-        rebase_path(runner_script, root_out_dir),
+        rebase_path(runner_script, root_build_dir),
         "--output-directory",
-        rebase_path(root_build_dir, root_build_dir),
+        ".",
         "--target-cpu",
         target_cpu,
         "--package",
-        rebase_path(_package_path, root_out_dir, root_build_dir),
+        rebase_path(_package_path, root_build_dir),
         "--package-name",
         _pkg_shortname,
         "--package-manifest",
-        rebase_path(_manifest_path),
+        rebase_path(_manifest_path, root_build_dir),
       ]
 
       if (defined(install_only) && install_only) {