Check if Rosetta 2 is enabled in the Conda and Docker runner checks

When on macOS on aarch64 hardware, the Conda runtime currently requires
Rosetta.  The Docker runtime does not require it, but can benefit from it
because our aarch64 image isn't totally free of x86_64 code (yet?),
so emulation is required and Rosetta is faster than QEMU.

The standalone installer still checks for Rosetta as we previously
didn't produce aarch64 standalone binaries¹, but that check will be made
conditional on Nextstrain CLI version in a subsequent commit² after the
first release of aarch64 support and these new Rosetta checks.

¹ <#357>
² <#358>

CHANGES.md

@@ -21,6 +21,15 @@ development source code and as such may not be routinely kept up to date.
   ([#357](https://github.com/nextstrain/cli/pull/357),
   [#358](https://github.com/nextstrain/cli/pull/358))
 
+* The Conda and Docker runtime checks performed by `nextstrain setup` and
+  `nextstrain check-setup` now test if Rosetta 2 is enabled for macOS on
+  aarch64 (aka arm64, Apple Silicon, M1/M2) hardware.  Rosetta is required for
+  the Conda runtime and optional, but recommended, for the Docker runtime.
+  Previously only the standalone installer checked for Rosetta, but starting
+  with this release it will not.
+  ([#361](https://github.com/nextstrain/cli/pull/361),
+  [#358](https://github.com/nextstrain/cli/pull/358))
+
 * `nextstrain build` now errors if a [development overlay option][] such as
   `--augur` or `--auspice` is given when using a runtime without support for
   those (anything but Docker or Singularity).  Previously, it would silently

nextstrain/cli/runner/conda.py

@@ -87,7 +87,7 @@
 from ..errors import InternalError
 from ..paths import RUNTIMES
 from ..types import Env, RunnerSetupStatus, RunnerTestResults, RunnerUpdateStatus
-from ..util import capture_output, colored, exec_or_return, runner_tests_ok, warn
+from ..util import capture_output, colored, exec_or_return, runner_tests_ok, test_rosetta_enabled, warn
 
 
 RUNTIME_ROOT = RUNTIMES / "conda/"
@@ -467,11 +467,12 @@ def supported_os() -> bool:
         else:
             return False
 
-
     return [
         ('operating system is supported',
             supported_os()),
 
+        *test_rosetta_enabled(),
+
         ("runtime data dir doesn't have spaces",
             " " not in str(RUNTIME_ROOT)),
     ]

nextstrain/cli/runner/docker.py

@@ -87,7 +87,7 @@
 from .. import config, env
 from ..errors import UserError
 from ..types import Env, RunnerSetupStatus, RunnerTestResults, RunnerTestResultStatus, RunnerUpdateStatus
-from ..util import warn, colored, capture_output, exec_or_return, split_image_name
+from ..util import warn, colored, capture_output, exec_or_return, split_image_name, test_rosetta_enabled
 from ..volume import store_volume, NamedVolume
 from ..__version__ import __version__
 
@@ -387,7 +387,12 @@ def test_image_version():
         ('docker run works',
             test_run()),
         *test_memory_limit(),
-        *test_image_version()
+        *test_image_version(),
+
+        # Rosetta 2 is optional, so convert False (fail) → None (warning)
+        *[(msg, None if status is False else status)
+            for msg, status
+             in test_rosetta_enabled("Rosetta 2 is enabled for faster execution (optional)")],
     ]
 
 

nextstrain/cli/util.py

@@ -16,7 +16,7 @@
 from wcmatch.glob import globmatch, GLOBSTAR, EXTGLOB, BRACE, MATCHBASE, NEGATE
 from .__version__ import __version__
 from .debug import debug
-from .types import RunnerModule, RunnerTestResults
+from .types import RunnerModule, RunnerTestResults, RunnerTestResultStatus
 
 
 def warn(*args):
@@ -603,6 +603,47 @@ def print_runner_tests(tests: RunnerTestResults):
         print(status.get(result, str(result)) + ":", formatted_description)
 
 
+def test_rosetta_enabled(msg: str = "Rosetta 2 is enabled") -> RunnerTestResults:
+    """
+    Check if Rosetta 2 is enabled (installed and active) on macOS aarch64
+    systems.
+    """
+    if (platform.system(), platform.machine()) != ("Darwin", "arm64"):
+        return []
+
+    status: RunnerTestResultStatus = ... # unknown
+
+    try:
+        subprocess.run(
+            ["pgrep", "-qU", "_oahd"],
+            stdin  = subprocess.DEVNULL,
+            stdout = subprocess.DEVNULL,
+            stderr = subprocess.DEVNULL,
+            check  = True)
+
+    except OSError:
+        status = ... # unknown; something's maybe wrong with our check
+
+    except subprocess.CalledProcessError as err:
+        if err.returncode > 0:
+            status = False
+            msg += dedent("""
+
+                To enable Rosetta, please run:
+
+                    softwareupdate --install-rosetta
+
+                and then try your setup or check-setup command again.\
+                """)
+        else:
+            status = None # warning; something's weird about the system
+            msg += " (unable to check!)"
+    else:
+        status = True
+
+    return [(msg, status)]
+
+
 # Copied without modification from lib/id3c/api/utils/__init__.py in the ID3C
 # project¹, which is licensed under the MIT license.  See the LICENSE.id3c file
 # distributed alongside this project's own LICENSE file.