Include en_001 locale, the default locale in swift-foundation

Author: kateinoigakukun

Example/Package.swift

@@ -4,14 +4,20 @@ import PackageDescription
 
 let package = Package(
     name: "Example",
+    traits: [
+        .default(enabledTraits: ["Slim"]),
+        "Slim",
+        "Minimal",
+    ],
     dependencies: [
         .package(name: "swift-icudata-slim", path: "../"),
     ],
     targets: [
         .executableTarget(
             name: "Example",
             dependencies: [
-                .product(name: "ICUDataSlim", package: "swift-icudata-slim"),
+                .product(name: "ICUDataSlim_Minimal", package: "swift-icudata-slim", condition: .when(traits: ["Minimal"])),
+                .product(name: "ICUDataSlim", package: "swift-icudata-slim", condition: .when(traits: ["Slim"]))
             ]
         ),
     ]

Example/Sources/Example/Example.swift

@@ -1,12 +1,13 @@
-// The Swift Programming Language
-// https://docs.swift.org/swift-book
-
 import Foundation
 
 @main
 struct Example {
     static func main() {
-        print("Available locales: \(Locale.availableIdentifiers.joined(separator: ", "))")
-        print("Available encodings: \(String.availableStringEncodings.map { "\($0)" }.joined(separator: ", "))")
+        print("Current locale: \(Locale.current.identifier)")
+        print("Available locales: \(Locale.availableIdentifiers)")
+        print("Available encodings: \(String.availableStringEncodings)")
+        let dateFormatter = DateFormatter()
+        dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss"
+        print("Parsing date: \(dateFormatter.date(from: "2023-10-01T12:00:00").map { "\($0)" } ?? "Failed to parse date!?")")
     }
 }

README.md

@@ -10,8 +10,8 @@ This package is especially useful for platforms that only support static linking
 | ICU Data Variant      | Data Size | Description |
 |:----------------------|----------:|---------------------------------------------|
 | Default               |   29.3 MB | Full ICU data, all locales and features |
-| `ICUDataSlim`         |    8.5 MB | Excludes some ICU features not used by Foundation; <br/> locale limited to `en_US` (see [default.json](./Scripts/filters/default.json)) |
-| `ICUDataSlim_Minimal` |    1.2 MB | Excludes even more features for a smaller footprint; <br/> locale limited to `en_US` (see [minimal.json](./Scripts/filters/minimal.json)) |
+| `ICUDataSlim`         |    8.6 MB | Excludes some ICU features not used by Foundation; <br/> locale limited to `en_001` (see [default.json](./Scripts/filters/default.json)) |
+| `ICUDataSlim_Minimal` |    1.5 MB | Excludes even more features for a smaller footprint; <br/> locale limited to `en_001` (see [minimal.json](./Scripts/filters/minimal.json)) |
 
 ## When to use minimal
 
@@ -57,6 +57,15 @@ See the [`Example`](./Example) directory for a complete setup.
 > [!WARNING]
 > The pre-compiled ICU data included in this package assumes a little endian platform. Big endian platforms are not supported. (Swift does not officially support big endian platforms though)
 
+## FAQ
+
+### Why is `en_001` used as the only available locale?
+
+The slimmed-down variants include only the `en_001` locale.
+On non-Apple platforms, the swift-foundation implementation *always* returns `en_001` by `Locale.current` regardless of environment variables or system locale settings.
+
+For more details, you can refer to the relevant implementation in the [swift-foundation source code](https://github.com/swiftlang/swift-foundation/blob/swift-6.2-DEVELOPMENT-SNAPSHOT-2025-07-08-a/Sources/FoundationEssentials/Locale/Locale_Unlocalized.swift#L39).
+
 ## License
 
 This project is licensed under the MIT License. See the [LICENSE](LICENSE) file for details.

Scripts/build-all.py

@@ -1,14 +1,14 @@
 #!/usr/bin/env python3
 import json
-import os
 import subprocess
 from pathlib import Path
+import shutil
 
 ICU_VERSIONS_FILE = Path(__file__).parent.parent / "icu-versions.json"
 PACKAGE_SCRIPT = Path(__file__).parent / "package-icudata.py"
 OUTPUT_BASE = Path(__file__).parent.parent / "Sources"
 
-def build_with_filter(filter_json: Path, filter_name: str, versions: dict):
+def build_with_filter(filter_json: Path, filter_name: str, versions: dict, args):
     print(f"Building with filter {filter_json}")
     icu_versions = set(versions["swift-icu-versions"].values())
     build_dir = Path(__file__).parent.parent / ".build" / "icu"
@@ -18,20 +18,29 @@ def build_with_filter(filter_json: Path, filter_name: str, versions: dict):
         out_dir.mkdir(parents=True, exist_ok=True)
         out_c = out_dir / filter_name / "icudata.c"
         print(f"Building ICU data {icu_version} -> {out_c}")
-        if out_c.exists():
+        if out_c.exists() and not args.clean:
             print(f"Skipping {out_c} because it already exists")
             continue
-        
+
+        per_filter_build_dir = build_dir / filter_name
+        if args.clean and per_filter_build_dir.exists():
+            print(f"Cleaning build directory {per_filter_build_dir}")
+            for item in per_filter_build_dir.iterdir():
+                if item.is_file():
+                    item.unlink()
+                else:
+                    shutil.rmtree(item)
+
         args = [
             "python3", str(PACKAGE_SCRIPT),
             "--icu-version", icu_version,
             "--filter-json", str(filter_json),
             "--output", str(out_c),
-            "--build-dir", str(build_dir / filter_name)
+            "--build-dir", str(per_filter_build_dir)
         ]
         print(f"Running {' '.join(args)}")
         subprocess.run(args, check=True)
-    
+
     for swift_version in versions["swift-icu-versions"]:
         icu_version = versions["swift-icu-versions"][swift_version]
         out_dir = OUTPUT_BASE / f"ICUDataSlim_{swift_version.replace('.', '_')}" / filter_name
@@ -41,19 +50,28 @@ def build_with_filter(filter_json: Path, filter_name: str, versions: dict):
         with open(out_c, "w") as f:
             f.write(f"// Generated by build-all.py\n")
             f.write(f"#include \"../../icudata/{icu_version}/{filter_name}/icudata.c\"\n")
-        
+
         out_empty_h = out_dir / "include" / "empty.h"
         out_empty_h.parent.mkdir(parents=True, exist_ok=True)
         out_empty_h.touch()
 
 
+def parse_args():
+    import argparse
+    parser = argparse.ArgumentParser(description="Build ICU data for all filters and versions.")
+    parser.add_argument("--clean", action="store_true", help="Clean build directories before building")
+    return parser.parse_args()
+
+
 def main():
+    args = parse_args()
     with open(ICU_VERSIONS_FILE) as f:
         versions = json.load(f)
-    
+
     filters_dir = Path(__file__).parent / "filters"
     for filter_file in filters_dir.glob("*.json"):
-        build_with_filter(filter_file, filter_file.stem, versions)
+        build_with_filter(filter_file, filter_file.stem, versions, args)
+
 
 if __name__ == "__main__":
     main()

Scripts/filters/default.json

@@ -3,7 +3,7 @@
         "filterType": "locale",
         "includeScripts": false,
         "includelist": [
-            "en_US"
+            "en_001"
         ]
     },
     "featureFilters": {
@@ -36,4 +36,4 @@
             "filterType": "exclude"
         }
     }
-}
+}

Scripts/filters/minimal.json

@@ -3,7 +3,7 @@
         "filterType": "locale",
         "includeScripts": false,
         "includelist": [
-            "en_US"
+            "en_001"
         ]
     },
     "featureFilters": {
@@ -44,15 +44,9 @@
         "zone_supplemental": {
             "filterType": "exclude"
         },
-        "locales_tree": {
-            "filterType": "exclude"
-        },
         "conversion_mappings": {
             "filterType": "exclude"
         },
-        "curr_tree": {
-            "filterType": "exclude"
-        },
         "translit": {
             "filterType": "exclude"
         },
@@ -66,4 +60,4 @@
             "filterType": "exclude"
         }
     }
-}
+}

Scripts/package-icudata.py

@@ -116,9 +116,9 @@ def main():
     build_dir = Path(args.build_dir)
     icu_src = download_and_extract(icu_url, build_dir, icu_version)
     destdir = build_dir / "destdir"
-    destdir.mkdir()
+    destdir.mkdir(parents=True, exist_ok=True)
     dat_path, version = build_icu(icu_src, Path(args.filter_json).absolute(), args.jobs, destdir)
     dat_to_c(dat_path, version, args.output)
 
 if __name__ == "__main__":
-    main()
+    main()