Allow for disabling of parallel processing of qmk find and qmk mass-compile. (#22160)

Co-authored-by: Duncan Sutherland <dunk2k_2000@hotmail.com>

lib/python/qmk/util.py

@@ -0,0 +1,56 @@
+"""Utility functions.
+"""
+import contextlib
+import multiprocessing
+
+from milc import cli
+
+
+@contextlib.contextmanager
+def parallelize():
+    """Returns a function that can be used in place of a map() call.
+
+    Attempts to use `mpire`, falling back to `multiprocessing` if it's not
+    available. If parallelization is not requested, returns the original map()
+    function.
+    """
+
+    # Work out if we've already got a config value for parallel searching
+    if cli.config.user.parallel_search is None:
+        parallel_search = True
+    else:
+        parallel_search = cli.config.user.parallel_search
+
+    # Non-parallel searches use `map()`
+    if not parallel_search:
+        yield map
+        return
+
+    # Prefer mpire's `WorkerPool` if it's available
+    with contextlib.suppress(ImportError):
+        from mpire import WorkerPool
+        from mpire.utils import make_single_arguments
+        with WorkerPool() as pool:
+
+            def _worker(func, *args):
+                # Ensure we don't unpack tuples -- mpire's `WorkerPool` tries to do so normally so we tell it not to.
+                for r in pool.imap_unordered(func, make_single_arguments(*args, generator=False), progress_bar=True):
+                    yield r
+
+            yield _worker
+        return
+
+    # Otherwise fall back to multiprocessing's `Pool`
+    with multiprocessing.Pool() as pool:
+        yield pool.imap_unordered
+
+
+def parallel_map(*args, **kwargs):
+    """Effectively runs `map()` but executes it in parallel if necessary.
+    """
+    with parallelize() as map_fn:
+        # This needs to be enclosed in a `list()` as some implementations return
+        # a generator function, which means the scope of the pool is closed off
+        # before the results are returned. Returning a list ensures results are
+        # materialised before any worker pool is shut down.
+        return list(map_fn(*args, **kwargs))