Add a default reader conditional for the current platform (#744)

Fixes #692

Author: chrisrink10

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
  * Added rudimentary support for `clojure.stacktrace` with `print-cause-trace` (part of #721)
  * Added support for `bytes` literals using a `#b` prefix (#732)
  * Added support for Python 3.12 (#734)
+ * Added a default reader conditional for the current platform (`windows`, `darwin`, `linux`, etc.) (#692)
 
 ### Changed
  * Basilisp now supports PyTest 7.0+ (#660)

docs/reader.rst

@@ -486,3 +486,11 @@ Basilisp takes advantage of this in :lpy:ns:`basilisp.io`.
                        (throw e))))
          :lpy38+ (.unlink (as-path f) ** :missing-ok (if silently true false)))
       silently))
+
+Platform Reader Features
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+Basilisp includes a specialized reader feature based on the current platform (Linux, MacOS, Windows, etc.).
+There exist cases where it may be required to use different APIs based on which platform is currently in use, so having a reader conditional to detect the current platform can simplify the development process across multiple platforms.
+The reader conditional name is always a keyword containing the lowercase version of the platform name as reported by ``platform.system()``.
+For example, if ``platform.system()`` returns the Python string ``"Windows"``, the platform specific reader conditional would be ``:windows``.

src/basilisp/io.lpy

@@ -33,12 +33,10 @@
   (as-path [f]
     (if (contains? #{"file" ""} (.-scheme f))
       (let [path (.-path f)]
-        (if (and (= sys/platform "win32") (os.path/isabs path))
-          ;; On MS-Windows, extracting an absolute path from the URL
-          ;; incorrectly adds a leading `/', .e.g. /C:\xyz.
-          (pathlib/Path (subs path 1))
-
-          (pathlib/Path path)))
+        ;; On MS-Windows, extracting an absolute path from the URL
+        ;; incorrectly adds a leading `/', .e.g. /C:\xyz.
+        (pathlib/Path #?(:windows (if (os.path/isabs path) (subs path 1) path)
+                         :default path)))
       (throw
        (ex-info "Cannot coerce non-File URL to pathlib.Path"
                 {:file f})))))

src/basilisp/lang/runtime.py

@@ -7,6 +7,7 @@
 import logging
 import math
 import numbers
+import platform
 import re
 import sys
 import threading
@@ -175,9 +176,11 @@ def _supported_python_versions_features() -> Iterable[kw.Keyword]:
 
 READER_COND_BASILISP_FEATURE_KW = kw.keyword("lpy")
 READER_COND_DEFAULT_FEATURE_KW = kw.keyword("default")
+READER_COND_PLATFORM = kw.keyword(platform.system().lower())
 READER_COND_DEFAULT_FEATURE_SET = lset.s(
     READER_COND_BASILISP_FEATURE_KW,
     READER_COND_DEFAULT_FEATURE_KW,
+    READER_COND_PLATFORM,
     *_supported_python_versions_features(),
 )
 

tests/basilisp/runtime_test.py

@@ -1,3 +1,4 @@
+import platform
 import sys
 from decimal import Decimal
 from fractions import Fraction
@@ -40,6 +41,7 @@ def test_is_supported_python_version():
                     "lpy310-",
                     "lpy311-",
                     "lpy312-",
+                    platform.system().lower(),
                 ],
             )
         ),
@@ -56,6 +58,7 @@ def test_is_supported_python_version():
                     "lpy310-",
                     "lpy311-",
                     "lpy312-",
+                    platform.system().lower(),
                 ],
             )
         ),
@@ -72,6 +75,7 @@ def test_is_supported_python_version():
                     "lpy310-",
                     "lpy39+",
                     "lpy38+",
+                    platform.system().lower(),
                 ],
             )
         ),
@@ -88,6 +92,7 @@ def test_is_supported_python_version():
                     "lpy310+",
                     "lpy39+",
                     "lpy38+",
+                    platform.system().lower(),
                 ],
             )
         ),
@@ -104,6 +109,7 @@ def test_is_supported_python_version():
                     "lpy311+",
                     "lpy39+",
                     "lpy38+",
+                    platform.system().lower(),
                 ],
             )
         ),