Custom default language specified by TLDR_LANGUAGE (#157)

Author: nebnola

README.md

@@ -63,6 +63,7 @@ export TLDR_COLOR_DESCRIPTION="white"
 export TLDR_COLOR_EXAMPLE="green"
 export TLDR_COLOR_COMMAND="red"
 export TLDR_COLOR_PARAMETER="white"
+export TLDR_LANGUAGE="es"
 export TLDR_CACHE_ENABLED=1
 export TLDR_CACHE_MAX_AGE=720
 export TLDR_PAGES_SOURCE_LOCATION="https://raw.githubusercontent.com/tldr-pages/tldr/master/pages"
@@ -120,12 +121,14 @@ Any of the values of above may be omitted. For example, you can do similar thing
 
 The language that tldr will use is dependent on a number of factors. If you specify a language via the
 `--language` flag, tldr will attempt to use that language and only that language. Otherwise, it will
-default to language set using `LANGUAGE` and `LANG` (ignoring the value `C` and `POSIX`).
+try to use the language specified by `TLDR_LANGUAGE`. If it is not set, or the page does not exist in that language,
+then tldr will use the
+language set using `LANGUAGE` and `LANG` (ignoring the values `C` and `POSIX`).
 If neither are set, then tldr will always attempt to get the `en` page. Finally, if `LANG` is set, it uses `LANGUAGE`, if set,
 first as the priority list to try languages in, followed by `LANG` if not included in `LANGUAGE`
 and `en` as fallback (assuming it does not already appear somewhere in `LANGUAGE` or `LANG`).
 All language values should be set to a value that follows [RFC 1766](https://tools.ietf.org/html/rfc1766.html),
-with the special exception of `C` and `POSIX` which is ignored.
+with the special exceptions of `C` and `POSIX` which are ignored.
 
 ### Remote source
 

tests/test_tldr.py

@@ -61,6 +61,23 @@ def test_get_default_language_unset(monkeypatch):
     assert tldr.get_default_language() is None
 
 
+@pytest.mark.parametrize("tldr_language, language, lang, expected", [
+    ("en", None, "fr_FR", ["en", "fr"]),
+    ("de", "ja_JA:cz_CZ", "cz_CZ", ["de", "ja", "cz", "en"]),
+    ("it", None, "C", ["it", "en"]),
+])
+def test_tldr_language(tldr_language, language, lang, expected, monkeypatch):
+    for name, var in [("TLDR_LANGUAGE", tldr_language),
+                      ("LANGUAGE", language),
+                      ("LANG", lang)]:
+        # Unset environment variable if their value is given as None
+        if var is None:
+            monkeypatch.delenv(name, raising=False)
+        else:
+            monkeypatch.setenv(name, var)
+    assert tldr.get_language_list() == expected
+
+
 @pytest.mark.parametrize("platform, expected", [
     ("linux2", "linux"),
     ("win32", "windows"),

tldr.py

@@ -184,6 +184,7 @@ def get_platform_list():
 
 
 def get_language_list():
+    tldr_language = get_language_code(os.environ.get('TLDR_LANGUAGE', ''))
     languages = os.environ.get('LANGUAGE', '').split(':')
     languages = list(map(
         get_language_code,
@@ -192,12 +193,19 @@ def get_language_list():
 
     default_lang = get_default_language()
 
-    if default_lang is not None and default_lang not in languages:
-        languages.append(default_lang)
-    else:
+    if default_lang is None:
         languages = []
+    elif default_lang not in languages:
+        languages.append(default_lang)
+    if tldr_language:
+        # remove tldr_language if it already exists to avoid double entry
+        try:
+            languages.remove(tldr_language)
+        except ValueError:
+            pass
+        languages.insert(0, tldr_language)
     if 'en' not in languages:
-        languages.append(None)
+        languages.append('en')
     return languages
 
 
@@ -338,8 +346,8 @@ def output(page):
 
 def update_cache(language=None):
     if language is None:
-        default_lang = get_default_language()
-        language = default_lang if default_lang is not None else 'en'
+        tldr_language = os.environ.get("TLDR_LANGUAGE", get_default_language())
+        language = tldr_language if tldr_language else 'en'
     elif isinstance(language, list):
         language = language[0]
     try: