From 4dc422e2ab330e31e1c6550ff3db2589db8db9b5 Mon Sep 17 00:00:00 2001
From: Roman Yurchak <rth.yurchak@gmail.com>
Date: Tue, 12 May 2020 12:33:20 +0200
Subject: [PATCH] Avoid duplicates in the list of built packages

---
 pyodide_build/buildall.py         |  3 ++-
 pyodide_build/common.py           | 10 +++++-----
 test/pyodide_build/test_common.py |  9 +++++++--
 3 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/pyodide_build/buildall.py b/pyodide_build/buildall.py
index 173b21782..162374693 100755
--- a/pyodide_build/buildall.py
+++ b/pyodide_build/buildall.py
@@ -106,7 +106,8 @@ def make_parser(parser):
         help='The path to the target Python installation')
     parser.add_argument(
         '--only', type=str, nargs='?', default=None,
-        help='Only build the specified packages')
+        help=('Only build the specified packages, provided as a comma '
+              'separated list'))
     return parser
 
 
diff --git a/pyodide_build/common.py b/pyodide_build/common.py
index ec9a35834..a82c10d30 100644
--- a/pyodide_build/common.py
+++ b/pyodide_build/common.py
@@ -1,5 +1,5 @@
 from pathlib import Path
-from typing import Optional, List
+from typing import Optional, Set
 
 
 ROOTDIR = Path(__file__).parents[1].resolve() / 'tools'
@@ -27,17 +27,17 @@ def parse_package(package):
         return yaml.load(fd)
 
 
-def _parse_package_subset(query: Optional[str]) -> Optional[List[str]]:
+def _parse_package_subset(query: Optional[str]) -> Optional[Set[str]]:
     """Parse the list of packages specified with PYODIDE_PACKAGES env var.
 
     Also add the list of mandatory packages: ['micropip', 'distlib']
 
     Returns:
-      a list of package names to build or None. The list may contain duplicate
-      values.
+      a set of package names to build or None.
     """
     if query is None:
         return None
     packages = query.split(',')
     packages = [el.strip() for el in packages]
-    return ['micropip', 'distlib'] + packages
+    packages = ['micropip', 'distlib'] + packages
+    return set(packages)
diff --git a/test/pyodide_build/test_common.py b/test/pyodide_build/test_common.py
index 05b2fe0bd..5fd05c1fb 100644
--- a/test/pyodide_build/test_common.py
+++ b/test/pyodide_build/test_common.py
@@ -9,6 +9,11 @@ from pyodide_build.common import _parse_package_subset  # noqa
 def test_parse_package_subset():
     assert _parse_package_subset(None) is None
     # micropip is always included
-    assert _parse_package_subset("numpy,pandas") == [
+    assert _parse_package_subset("numpy,pandas") == {
         'micropip', 'distlib', 'numpy', 'pandas'
-    ]
+    }
+
+    # duplicates are removed
+    assert _parse_package_subset("numpy,numpy") == {
+        'micropip', 'distlib', 'numpy'
+    }