Cleanup GoArchiveData runfiles handling (#4024)

**What type of PR is this?**
Starlark cleanup

**What does this PR do? Why is it needed?**
We don't need to make copies of the lists

**Which issues(s) does this PR fix?**

Fixes #

**Other notes for review**

Author: dzbarsky

go/private/actions/archive.bzl

@@ -69,15 +69,13 @@ def emit_archive(go, source = None, _recompile_suffix = "", recompile_internal_d
         out_nogo_validation = go.declare_file(go, name = source.library.name, ext = pre_ext + ".nogo")
 
     direct = [get_archive(dep) for dep in source.deps]
-    runfiles = source.runfiles
-    data_files = runfiles.files
 
     files = []
     for a in direct:
         files.append(a.runfiles)
         if a.source.mode != go.mode:
             fail("Archive mode does not match {} is {} expected {}".format(a.data.label, mode_string(a.source.mode), mode_string(go.mode)))
-    runfiles = runfiles.merge_all(files)
+    runfiles = source.runfiles.merge_all(files)
 
     importmap = "main" if source.library.is_main else source.library.importmap
     importpath, _ = effective_importpath_pkgpath(source.library)
@@ -189,7 +187,7 @@ def emit_archive(go, source = None, _recompile_suffix = "", recompile_internal_d
         file = out_lib,
         export_file = out_export,
         facts_file = out_facts,
-        data_files = as_tuple(data_files),
+        runfiles = source.runfiles,
         _validation_output = out_nogo_validation,
         _cgo_deps = as_tuple(cgo_deps),
     )

go/private/rules/test.bzl

@@ -679,7 +679,7 @@ def _recompile_external_deps(go, external_source, internal_archive, library_labe
             x_defs = dict(arc_data._x_defs),
             deps = deps,
             gc_goopts = as_list(arc_data._gc_goopts),
-            runfiles = go._ctx.runfiles(files = arc_data.data_files),
+            runfiles = arc_data.runfiles,
             cgo = arc_data._cgo,
             cdeps = as_list(arc_data._cdeps),
             cppopts = as_list(arc_data._cppopts),

go/private/tools/path.bzl

@@ -58,14 +58,13 @@ def _go_path_impl(ctx):
                 importpath = importpath,
                 dir = "src/" + pkgpath,
                 srcs = as_list(archive.orig_srcs),
-                data = as_list(archive.data_files),
+                runfiles = archive.runfiles,
                 embedsrcs = as_list(archive._embedsrcs),
                 pkgs = {mode: archive.file},
             )
             if pkgpath in pkg_map:
-                _merge_pkg(pkg_map[pkgpath], pkg)
-            else:
-                pkg_map[pkgpath] = pkg
+                pkg = _merge_pkg(pkg_map[pkgpath], pkg)
+            pkg_map[pkgpath] = pkg
 
     # Build a manifest file that includes all files to copy/link/zip.
     inputs = []
@@ -95,7 +94,7 @@ def _go_path_impl(ctx):
                 _add_manifest_entry(manifest_entries, manifest_entry_map, inputs, f, dst)
     if ctx.attr.include_data:
         for pkg in pkg_map.values():
-            for f in pkg.data:
+            for f in pkg.runfiles.files.to_list():
                 parts = f.path.split("/")
                 if "testdata" in parts:
                     i = parts.index("testdata")
@@ -261,12 +260,21 @@ go_path = rule(
 
 def _merge_pkg(x, y):
     x_srcs = {f.path: None for f in x.srcs}
-    x_data = {f.path: None for f in x.data}
     x_embedsrcs = {f.path: None for f in x.embedsrcs}
-    x.srcs.extend([f for f in y.srcs if f.path not in x_srcs])
-    x.data.extend([f for f in y.data if f.path not in x_data])
-    x.embedsrcs.extend([f for f in y.embedsrcs if f.path not in x_embedsrcs])
-    x.pkgs.update(y.pkgs)
+
+    # Not all bazel versions support `dict1 | dict2` yet.
+    pkgs = dict()
+    pkgs.update(x.pkgs)
+    pkgs.update(y.pkgs)
+
+    return struct(
+        importpath = x.importpath,
+        dir = x.dir,
+        srcs = x.srcs + [f for f in y.srcs if f.path not in x_srcs],
+        runfiles = x.runfiles.merge(y.runfiles),
+        embedsrcs = x.embedsrcs + [f for f in y.embedsrcs if f.path not in x_embedsrcs],
+        pkgs = pkgs,
+    )
 
 def _add_manifest_entry(entries, entry_map, inputs, src, dst):
     if dst in entry_map:

go/providers.rst

@@ -274,7 +274,7 @@ rule.  Instead, it's referenced in the ``data`` field of GoArchive_.
 +--------------------------------+-----------------------------------------------------------------+
 | The unmodified sources provided to the rule, including .go, .s, .h, .c files.                    |
 +--------------------------------+-----------------------------------------------------------------+
-| :param:`data_files`            | :type:`tuple of File`                                           |
+| :param:`runfiles`              | :type:`runfiles`                                           |
 +--------------------------------+-----------------------------------------------------------------+
 | Data files that should be available at runtime to binaries and tests built                       |
 | from this archive.                                                                               |