Import on Pyodide, which has no thread_time_ns

CHANGELOG.md

@@ -173,6 +173,8 @@
 
 ### Fixed
 
+- `import scope_profiler` works on Pyodide, whose `time` has no `thread_time_ns`; the process
+  clock stands in for it there.
 - Summary: a recursive row's total sums only the outermost calls, so it no longer
   exceeds the time of its caller, and the regions called from a recursive
   function are no longer marked with the recursive symbol (#313).

src/scope_profiler/concurrency.py

@@ -35,7 +35,12 @@
 import sys
 import threading
 import weakref
-from time import perf_counter_ns, thread_time_ns
+from time import perf_counter_ns
+
+try:
+    from time import thread_time_ns
+except ImportError:  # Emscripten (Pyodide): no per-thread clock, and only one thread
+    from time import process_time_ns as thread_time_ns
 from typing import Any
 
 import numpy as np

src/scope_profiler/tests/unit/test_concurrency.py

@@ -1,6 +1,8 @@
 """The lane bookkeeping behind ``track_threads`` and ``track_async``."""
 
 import asyncio
+import subprocess
+import sys
 import threading
 
 import numpy as np
@@ -316,3 +318,15 @@ def previous(frame, event, arg):
         sys.setprofile(None)
         tracker.uninstall()
         threading.setprofile(None)
+
+
+def test_imports_without_a_per_thread_clock():
+    """Pyodide's ``time`` has no ``thread_time_ns``; the process clock stands in."""
+    code = (
+        "import time\n"
+        "del time.thread_time_ns\n"
+        "import scope_profiler\n"
+        "from scope_profiler import concurrency\n"
+        "assert concurrency.thread_time_ns is time.process_time_ns\n"
+    )
+    subprocess.run([sys.executable, "-c", code], check=True)