docker.bzl: Detect if local Docker image is used

Signed-off-by: Eryk Szpotanski <[email protected]>

docker.bzl

@@ -14,11 +14,31 @@ def _impl(repository_ctx):
     if not docker:
         fail("Failed to find {}.".format(docker_name))
 
+    image_id = repository_ctx.attr.sha256
+    inspect = repository_ctx.execute([
+        docker,
+        "inspect",
+        "--type=image",
+        image_id,
+    ])
+    if inspect.return_code != 0:
+        pull = repository_ctx.execute([
+            docker,
+            "pull",
+            image,
+        ])
+        if pull.return_code != 0:
+            fail("Image {} cannot be pulled: {}".format(image, pull.stderr), pull.return_code)
+        image_id = image
+        repository_ctx.report_progress("Pulled {}.".format(repository_ctx.attr.image))
+    else:
+        repository_ctx.report_progress("Using local {}.".format(repository_ctx.attr.image))
+
     created = repository_ctx.execute(
         [
             docker,
             "create",
-            image,
+            image_id,
         ],
     )
     if created.return_code != 0: