Refactor all the input processing code. (#756)

* Refactor all the input processing code.

- Create a MappingContext to hold behaviors and defaults
- Change calls
  - from `process_x(ctx, content_map, ..., default_x, default_y, ...)`
  - to `process_x(mapping_context, ...)

1. This brings the code more in line with the new preferred rule writing style.
1. A major motivation for the change is adding include_runfiles to pkg_tar, where we want
   to sometimes have add_label_list do the runfiles inclusion for us, and
   other times we want to revert to legacy behavior. If we always passed it
   in `ctx`, that would not be possible.

* Syle nits
* make buildifier happier

pkg/install.bzl

@@ -17,28 +17,20 @@ This module provides an interface (`pkg_install`) for creating a `bazel
 run`-able installation script.
 """
 
-load("//pkg:providers.bzl", "PackageDirsInfo", "PackageFilegroupInfo", "PackageFilesInfo", "PackageSymlinkInfo")
-load("//pkg/private:pkg_files.bzl", "process_src", "write_manifest")
 load("@rules_python//python:defs.bzl", "py_binary")
+load("//pkg:providers.bzl", "PackageDirsInfo", "PackageFilegroupInfo", "PackageFilesInfo", "PackageSymlinkInfo")
+load("//pkg/private:pkg_files.bzl", "create_mapping_context_from_ctx", "process_src", "write_manifest")
 
 def _pkg_install_script_impl(ctx):
     script_file = ctx.actions.declare_file(ctx.attr.name + ".py")
 
     fragments = []
-    files_to_run = []
-    content_map = {}
+    mapping_context = create_mapping_context_from_ctx(ctx, label = ctx.label, default_mode = "0644")
     for src in ctx.attr.srcs:
         process_src(
-            ctx,
-            content_map,
-            files_to_run,
+            mapping_context,
             src = src,
             origin = src.label,
-            default_mode = "0644",
-            default_user = None,
-            default_group = None,
-            default_uid = None,
-            default_gid = None,
         )
 
     manifest_file = ctx.actions.declare_file(ctx.attr.name + "-install-manifest.json")
@@ -49,14 +41,14 @@ def _pkg_install_script_impl(ctx):
     # Note that these paths are different when used as tools run within a build.
     # See also
     # https://docs.bazel.build/versions/4.1.0/skylark/rules.html#tools-with-runfiles
-    write_manifest(ctx, manifest_file, content_map, use_short_path = True)
+    write_manifest(ctx, manifest_file, mapping_context.content_map, use_short_path = True)
 
     # Get the label of the actual py_binary used to run this script.
     #
     # This is super brittle, but I don't know how to otherwise get this
     # information without creating a circular dependency given the current state
     # of rules_python.
-    
+
     # The name of the binary is the name of this target, minus
     # "_install_script".
     label_str = str(ctx.label)[:-len("_install_script")]
@@ -77,7 +69,7 @@ def _pkg_install_script_impl(ctx):
 
     my_runfiles = ctx.runfiles(
         files = [manifest_file],
-        transitive_files = depset(transitive = files_to_run),
+        transitive_files = depset(transitive = mapping_context.file_deps),
     )
 
     return [
@@ -147,7 +139,7 @@ def pkg_install(name, srcs, **kwargs):
     ```
     bazel run -- //path/to:install --help
     ```
-    
+
     WARNING: While this rule does function when being run from within a bazel
     rule, such use is not recommended.  If you do, **always** use the
     `--destdir` argument to specify the desired location for the installation to

pkg/path.bzl

@@ -11,8 +11,10 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-"""Helper functions that don't depend on Skylark, so can be unit tested."""
+"""Helper functions that don't depend on Starlark, so can be unit tested."""
 
+# buildifier: disable=function-docstring-args
+# buildifier: disable=function-docstring-return
 def safe_short_path(file_):
     """Like `File.short_path` but safe for use with files from external repositories.
     """
@@ -27,9 +29,10 @@ def safe_short_path(file_):
     # Beginning with `file_.path`, remove optional `F.root.path`.
     working_path = file_.path
     if not file_.is_source:
-        working_path = working_path[len(file_.root.path)+1:]
+        working_path = working_path[len(file_.root.path) + 1:]
     return working_path
 
+# buildifier: disable=function-docstring-args,function-docstring-return
 def _short_path_dirname(path):
     """Returns the directory's name of the short path of an artifact."""
     sp = safe_short_path(path)
@@ -39,6 +42,8 @@ def _short_path_dirname(path):
         return ""
     return sp[:last_pkg]
 
+# buildifier: disable=function-docstring-args
+# buildifier: disable=function-docstring-return
 def dest_path(f, strip_prefix, data_path_without_prefix = ""):
     """Returns the short path of f, stripped of strip_prefix."""
     f_short_path = safe_short_path(f)
@@ -56,32 +61,33 @@ def dest_path(f, strip_prefix, data_path_without_prefix = ""):
 
         # Avoid stripping prefix if final directory is incomplete
         if prefix_last_dir not in f_short_path.split("/"):
-          strip_prefix = data_path_without_prefix
+            strip_prefix = data_path_without_prefix
 
         return f_short_path[len(strip_prefix):]
     return f_short_path
 
-def compute_data_path(ctx, data_path):
+def compute_data_path(label, data_path):
     """Compute the relative data path prefix from the data_path attribute.
 
     Args:
-      ctx: rule implementation ctx.
-      data_path: path to a file, relative to the package of the rule ctx.
+        label: target label
+        data_path: path to a file, relative to the package of the label.
+    Returns:
+        str
     """
-    build_dir = ctx.label.package
     if data_path:
         # Strip ./ from the beginning if specified.
         # There is no way to handle .// correctly (no function that would make
-        # that possible and Skylark is not turing complete) so just consider it
+        # that possible and Starlark is not turing complete) so just consider it
         # as an absolute path.
         if len(data_path) >= 2 and data_path[0:2] == "./":
             data_path = data_path[2:]
         if not data_path or data_path == ".":  # Relative to current package
-            return build_dir
+            return label.package
         elif data_path[0] == "/":  # Absolute path
             return data_path[1:]
         else:  # Relative to a sub-directory
-            tmp_short_path_dirname = build_dir
+            tmp_short_path_dirname = label.package
             if tmp_short_path_dirname:
                 return tmp_short_path_dirname + "/" + data_path
             return data_path