GH-137243: Have Tools/wasm/wasi detect WASI SDK installs in /opt when the release tarball is extracted (GH-137244)

(cherry picked from commit 2f1a9f2)

Co-authored-by: Brett Cannon <brett@python.org>

Author: brettcannon

Misc/NEWS.d/next/Tools-Demos/2025-07-30-10-28-35.gh-issue-137243.NkdUqH.rst

@@ -0,0 +1,2 @@
+Have Tools/wasm/wasi detect a WASI SDK install in /opt when it was directly
+extracted from a release tarball.

Tools/wasm/wasi/__main__.py

@@ -25,6 +25,8 @@
 LOCAL_SETUP = CHECKOUT / "Modules" / "Setup.local"
 LOCAL_SETUP_MARKER = "# Generated by Tools/wasm/wasi.py\n".encode("utf-8")
 
+WASI_SDK_VERSION = 24
+
 WASMTIME_VAR_NAME = "WASMTIME"
 WASMTIME_HOST_RUNNER_VAR = f"{{{WASMTIME_VAR_NAME}}}"
 
@@ -169,10 +171,22 @@ def make_build_python(context, working_dir):
 
 
 def find_wasi_sdk():
-    """Find the path to wasi-sdk."""
+    """Find the path to the WASI SDK."""
     if wasi_sdk_path := os.environ.get("WASI_SDK_PATH"):
         return pathlib.Path(wasi_sdk_path)
-    elif (default_path := pathlib.Path("/opt/wasi-sdk")).exists():
+
+    opt_path = pathlib.Path("/opt")
+    # WASI SDK versions have a ``.0`` suffix, but it's a constant; the WASI SDK team
+    # has said they don't plan to ever do a point release and all of their Git tags
+    # lack the ``.0`` suffix.
+    # Starting with WASI SDK 23, the tarballs went from containing a directory named
+    # ``wasi-sdk-{WASI_SDK_VERSION}.0`` to e.g.
+    # ``wasi-sdk-{WASI_SDK_VERSION}.0-x86_64-linux``.
+    potential_sdks = [path for path in opt_path.glob(f"wasi-sdk-{WASI_SDK_VERSION}.0*")
+                      if path.is_dir()]
+    if len(potential_sdks) == 1:
+        return potential_sdks[0]
+    elif (default_path := opt_path / "wasi-sdk").is_dir():
         return default_path
 
 
@@ -303,6 +317,8 @@ def clean_contents(context):
 
 
 def main():
+    default_host_triple = "wasm32-wasip1"
+    default_wasi_sdk = find_wasi_sdk()
     default_host_runner = (f"{WASMTIME_HOST_RUNNER_VAR} run "
                         # Make sure the stack size will work for a pydebug
                         # build.
@@ -346,17 +362,17 @@ def main():
     for subcommand in build, configure_host:
         subcommand.add_argument("--wasi-sdk", type=pathlib.Path,
                                 dest="wasi_sdk_path",
-                                default=find_wasi_sdk(),
-                                help="Path to wasi-sdk; defaults to "
-                                     "$WASI_SDK_PATH or /opt/wasi-sdk")
+                                default=default_wasi_sdk,
+                                help=f"Path to the WASI SDK; defaults to {default_wasi_sdk}")
         subcommand.add_argument("--host-runner", action="store",
                         default=default_host_runner, dest="host_runner",
-                        help="Command template for running the WASI host "
-                             "(default designed for wasmtime 14 or newer: "
-                                f"`{default_host_runner}`)")
+                        help="Command template for running the WASI host; defaults to "
+                             f"`{default_host_runner}`")
     for subcommand in build, configure_host, make_host:
-        subcommand.add_argument("--host-triple", action="store", default="wasm32-wasip1",
-                        help="The target triple for the WASI host build")
+        subcommand.add_argument("--host-triple", action="store",
+                                default=default_host_triple,
+                                help="The target triple for the WASI host build; "
+                                    f"defaults to {default_host_triple}")
 
     context = parser.parse_args()
     context.init_dir = pathlib.Path().absolute()