Transition container image target platform

Transition to the target platform associated with the `architecture` and
`operating_system` attributes on container image rules.

This change allows for container image rules to build the correct binary for
the target platform, regardless of the host platform. Container image rules
would require the use of the `target_compatible_with` attribute to prevent
mismatching host and target platforms building dependencies incorrectly.
Additionally, hosts which did not match the target platform had to explicitly
specify the target platform with the `--platforms` command-line option.

This change fixes the aforementioned issues and
#690.

Massive thank you to @joneshf for the initial source. It has been adapted to
automatically select the target platform associated with the container image,
as opposed to always using `@io_bazel_rules_go//go/toolchain:linux_amd64`.

container/image.bzl

@@ -324,6 +324,7 @@ def _impl(
             executable = True,
             outputs = _container.image.outputs,
             implementation = _impl,
+            cfg = _container.image.cfg,
         )
 
     Args:
@@ -625,7 +626,7 @@ _attrs = dicts.add(_layer.attrs, {
         Acceptable formats: Integer or floating point seconds since Unix Epoch, RFC 3339 date/time.
 
         This field supports stamp variables.
-        
+
         If not set, defaults to {BUILD_TIMESTAMP} when stamp = True, otherwise 0""",
     ),
     "docker_run_flags": attr.string(
@@ -637,14 +638,14 @@ _attrs = dicts.add(_layer.attrs, {
         doc = """List of entrypoints to add in the image.
 
         See https://docs.docker.com/engine/reference/builder/#entrypoint
-                
+
         Set `entrypoint` to `None`, `[]` or `""` will set the `Entrypoint` of the image
         to be `null`.
 
         The behavior between using `""` and `[]` may differ.
         Please see [#1448](https://github.com/bazelbuild/rules_docker/issues/1448)
         for more details.
-    
+
         This field supports stamp variables.""",
     ),
     "experimental_tarball_format": attr.string(
@@ -667,12 +668,12 @@ _attrs = dicts.add(_layer.attrs, {
     ),
     "labels": attr.string_dict(
         doc = """Dictionary from custom metadata names to their values.
-        
+
         See https://docs.docker.com/engine/reference/builder/#label
-        
+
         You can also put a file name prefixed by '@' as a value.
         Then the value is replaced with the contents of the file.
-        
+
         Example:
 
             labels = {
@@ -699,7 +700,7 @@ _attrs = dicts.add(_layer.attrs, {
     ),
     "layers": attr.label_list(
         doc = """List of `container_layer` targets.
-        
+
         The data from each `container_layer` will be part of container image,
         and the environment variable will be available in the image as well.""",
         providers = [LayerInfo],
@@ -731,7 +732,7 @@ _attrs = dicts.add(_layer.attrs, {
     # Starlark doesn't support int_list...
     "ports": attr.string_list(
         doc = """List of ports to expose.
-        
+
         See https://docs.docker.com/engine/reference/builder/#expose""",
     ),
     "repository": attr.string(
@@ -741,7 +742,7 @@ _attrs = dicts.add(_layer.attrs, {
         Images generated by `container_image` are tagged by default to
         `bazel/package_name:target` for a `container_image` target at
         `//package/name:target`.
-        
+
         Setting this attribute to `gcr.io/dummy` would set the default tag to
         `gcr.io/dummy/package_name:target`.""",
     ),
@@ -767,19 +768,22 @@ _attrs = dicts.add(_layer.attrs, {
     ),
     "volumes": attr.string_list(
         doc = """List of volumes to mount.
-        
+
         See https://docs.docker.com/engine/reference/builder/#volumes""",
     ),
     "workdir": attr.string(
         doc = """Initial working directory when running the Docker image.
 
         See https://docs.docker.com/engine/reference/builder/#workdir
-        
+
         Because building the image never happens inside a Docker container,
         this working directory does not affect the other actions (e.g., adding files).
 
         This field supports stamp variables.""",
     ),
+    "_allowlist_function_transition": attr.label(
+        default = "@bazel_tools//tools/allowlists/function_transition_allowlist",
+    ),
     "_digester": attr.label(
         default = "//container/go/cmd/digester",
         cfg = "host",
@@ -799,19 +803,40 @@ _outputs["config_digest"] = "%{name}.json.sha256"
 
 _outputs["build_script"] = "%{name}.executable"
 
+def _image_transition_impl(settings, attr):
+    # Architecture aliases.
+    architecture = {
+        "386": "x86_32",
+        "amd64": "x86_64",
+        "ppc64le": "ppc",
+    }.get(attr.architecture, attr.architecture)
+    return dicts.add(settings, {
+        "//command_line_option:platforms": "//platforms:{}_{}".format(attr.operating_system, architecture),
+    })
+
+_image_transition = transition(
+    implementation = _image_transition_impl,
+    inputs = [],
+    outputs = [
+        "//command_line_option:platforms",
+    ],
+)
+
 image = struct(
     attrs = _attrs,
     outputs = _outputs,
     implementation = _impl,
+    cfg = _image_transition,
 )
 
 container_image_ = rule(
-    attrs = _attrs,
+    attrs = image.attrs,
     doc = "Called by the `container_image` macro with **kwargs, see below",
     executable = True,
-    outputs = _outputs,
+    outputs = image.outputs,
     toolchains = ["@io_bazel_rules_docker//toolchains/docker:toolchain_type"],
-    implementation = _impl,
+    implementation = image.implementation,
+    cfg = image.cfg,
 )
 
 # This validates the two forms of value accepted by

container/layer.bzl

@@ -294,7 +294,7 @@ _layer_attrs = dicts.add({
     "compression_options": attr.string_list(),
     "data_path": attr.string(
         doc = """Root path of the files.
-        
+
         The directory structure from the files is preserved inside the
         Docker image, but a prefix path determined by `data_path`
         is removed from the directory structure. This path can
@@ -307,7 +307,7 @@ _layer_attrs = dicts.add({
     "debs": attr.label_list(
         allow_files = deb_filetype,
         doc = """Debian packages to extract.
-        
+
         Deprecated: A list of debian packages that will be extracted in the Docker image.
         Note that this doesn't actually install the packages. Installation needs apt
         or apt-get which need to be executed within a running container which
@@ -316,7 +316,7 @@ _layer_attrs = dicts.add({
     "directory": attr.string(
         default = "/",
         doc = """Target directory.
-        
+
         The directory in which to expand the specified files, defaulting to '/'.
         Only makes sense accompanying one of files/tars/debs.""",
     ),
@@ -326,16 +326,16 @@ _layer_attrs = dicts.add({
     "enable_mtime_preservation": attr.bool(default = False),
     "env": attr.string_dict(
         doc = """Dictionary from environment variable names to their values when running the Docker image.
-       
+
         See https://docs.docker.com/engine/reference/builder/#env
 
         For example,
 
             env = {
                 "FOO": "bar",
                 ...
-            }, 
-        
+            },
+
         The values of this field support make variables (e.g., `$(FOO)`)
         and stamp variables; keys support make variables as well.""",
     ),
@@ -357,9 +357,9 @@ _layer_attrs = dicts.add({
     "portable_mtime": attr.bool(default = False),
     "symlinks": attr.string_dict(
         doc = """Symlinks to create in the Docker image.
-        
+
         For example,
-        
+
             symlinks = {
                 "/path/to/link": "/path/to/target",
                 ...
@@ -369,7 +369,7 @@ _layer_attrs = dicts.add({
     "tars": attr.label_list(
         allow_files = tar_filetype,
         doc = """Tar file to extract in the layer.
-        
+
         A list of tar files whose content should be in the Docker image.""",
     ),
 }, _hash_tools, _layer_tools, _zip_tools)
@@ -387,10 +387,10 @@ layer = struct(
 
 container_layer_ = rule(
     doc = _DOC,
-    attrs = _layer_attrs,
+    attrs = layer.attrs,
     executable = False,
-    outputs = _layer_outputs,
-    implementation = _impl,
+    outputs = layer.outputs,
+    implementation = layer.implementation,
     toolchains = ["@io_bazel_rules_docker//toolchains/docker:toolchain_type"],
 )
 

contrib/repro_test.bzl

@@ -328,4 +328,5 @@ container_repro_test = rule(
     }),
     test = True,
     toolchains = ["@io_bazel_rules_docker//toolchains/docker:toolchain_type"],
+    cfg = _container.image.cfg,
 )

docker/package_managers/apt_key.bzl

@@ -155,12 +155,14 @@ key = struct(
     attrs = _attrs,
     outputs = _outputs,
     implementation = _impl,
+    cfg = _container.image.cfg,
 )
 
 add_apt_key = rule(
-    attrs = _attrs,
-    outputs = _outputs,
-    implementation = _impl,
+    attrs = key.attrs,
+    outputs = key.outputs,
+    implementation = key.implementation,
     toolchains = ["@io_bazel_rules_docker//toolchains/docker:toolchain_type"],
     executable = True,
+    cfg = key.cfg,
 )

docker/toolchain_container/toolchain_container.bzl

@@ -243,6 +243,7 @@ language_tool_layer_ = rule(
     outputs = _container.image.outputs,
     toolchains = ["@io_bazel_rules_docker//toolchains/docker:toolchain_type"],
     implementation = _language_tool_layer_impl,
+    cfg = _container.image.cfg,
 )
 
 def language_tool_layer(**kwargs):
@@ -350,6 +351,7 @@ toolchain_container_ = rule(
     outputs = _container.image.outputs,
     toolchains = ["@io_bazel_rules_docker//toolchains/docker:toolchain_type"],
     implementation = _toolchain_container_impl,
+    cfg = _container.image.cfg,
 )
 
 def toolchain_container(**kwargs):

docs/container.md

@@ -108,7 +108,7 @@ A rule that assembles data into a tarball which can be use as in layers attr in
 | <a id="container_layer-empty_dirs"></a>empty_dirs |  -   | List of strings | optional | [] |
 | <a id="container_layer-empty_files"></a>empty_files |  -   | List of strings | optional | [] |
 | <a id="container_layer-enable_mtime_preservation"></a>enable_mtime_preservation |  -   | Boolean | optional | False |
-| <a id="container_layer-env"></a>env |  Dictionary from environment variable names to their values when running the Docker image.<br><br>        See https://docs.docker.com/engine/reference/builder/#env<br><br>        For example,<br><br>            env = {                 "FOO": "bar",                 ...             }, <br><br>        The values of this field support make variables (e.g., <code>$(FOO)</code>)         and stamp variables; keys support make variables as well.   | <a href="https://bazel.build/docs/skylark/lib/dict.html">Dictionary: String -> String</a> | optional | {} |
+| <a id="container_layer-env"></a>env |  Dictionary from environment variable names to their values when running the Docker image.<br><br>        See https://docs.docker.com/engine/reference/builder/#env<br><br>        For example,<br><br>            env = {                 "FOO": "bar",                 ...             },<br><br>        The values of this field support make variables (e.g., <code>$(FOO)</code>)         and stamp variables; keys support make variables as well.   | <a href="https://bazel.build/docs/skylark/lib/dict.html">Dictionary: String -> String</a> | optional | {} |
 | <a id="container_layer-extract_config"></a>extract_config |  -   | <a href="https://bazel.build/docs/build-ref.html#labels">Label</a> | optional | //container/go/cmd/extract_config:extract_config |
 | <a id="container_layer-files"></a>files |  File to add to the layer.<br><br>        A list of files that should be included in the Docker image.   | <a href="https://bazel.build/docs/build-ref.html#labels">List of labels</a> | optional | [] |
 | <a id="container_layer-incremental_load_template"></a>incremental_load_template |  -   | <a href="https://bazel.build/docs/build-ref.html#labels">Label</a> | optional | //container:incremental_load_template |
@@ -414,6 +414,7 @@ You can write a customized container_image rule by writing something like:
         executable = True,
         outputs = _container.image.outputs,
         implementation = _impl,
+        cfg = _container.image.cfg,
     )
 
 

java/image.bzl

@@ -163,6 +163,7 @@ jar_dep_layer = rule(
     outputs = lang_image.outputs,
     toolchains = lang_image.toolchains,
     implementation = _jar_dep_layer_impl,
+    cfg = lang_image.cfg,
 )
 
 def _jar_app_layer_impl(ctx):
@@ -255,6 +256,7 @@ jar_app_layer = rule(
     outputs = _container.image.outputs,
     toolchains = ["@io_bazel_rules_docker//toolchains/docker:toolchain_type"],
     implementation = _jar_app_layer_impl,
+    cfg = _container.image.cfg,
 )
 
 def java_image(
@@ -362,6 +364,7 @@ _war_dep_layer = rule(
     outputs = _container.image.outputs,
     toolchains = ["@io_bazel_rules_docker//toolchains/docker:toolchain_type"],
     implementation = _war_dep_layer_impl,
+    cfg = _container.image.cfg,
 )
 
 def _war_app_layer_impl(ctx):
@@ -400,6 +403,7 @@ _war_app_layer = rule(
     outputs = _container.image.outputs,
     toolchains = ["@io_bazel_rules_docker//toolchains/docker:toolchain_type"],
     implementation = _war_app_layer_impl,
+    cfg = _container.image.cfg,
 )
 
 def war_image(name, base = None, deps = [], layers = [], **kwargs):

lang/image.bzl

@@ -272,6 +272,7 @@ image = struct(
     outputs = _container.image.outputs,
     toolchains = ["@io_bazel_rules_docker//toolchains/docker:toolchain_type"],
     implementation = _app_layer_impl,
+    cfg = _container.image.cfg,
 )
 
 _app_layer = rule(
@@ -280,6 +281,7 @@ _app_layer = rule(
     outputs = image.outputs,
     toolchains = image.toolchains,
     implementation = image.implementation,
+    cfg = image.cfg,
 )
 
 # Convenience function that instantiates the _app_layer rule and returns

nodejs/image.bzl

@@ -86,6 +86,7 @@ _dep_layer = rule(
     outputs = lang_image.outputs,
     toolchains = lang_image.toolchains,
     implementation = _dep_layer_impl,
+    cfg = lang_image.cfg,
 )
 
 def _npm_deps_runfiles(dep):
@@ -107,6 +108,7 @@ _npm_deps_layer = rule(
     outputs = lang_image.outputs,
     toolchains = lang_image.toolchains,
     implementation = _npm_deps_layer_impl,
+    cfg = lang_image.cfg,
 )
 
 def nodejs_image(