Use Lingua instead of pycld3 for language detection. Fixes #593

annif/transform/__init__.py

@@ -48,4 +48,4 @@ def get_transform(transform_specs, project):
     _transforms.update({langfilter.LangFilter.name: langfilter.LangFilter})
 except ImportError:
     annif.logger.debug(
-        "pycld3 not available, not enabling filter_language transform")
+        "Lingua not available, not enabling filter_language transform")

annif/transform/langfilter.py

@@ -2,7 +2,7 @@
 different from the language of the project."""
 
 import annif
-import cld3
+import lingua
 from . import transform
 
 logger = annif.logger
@@ -16,14 +16,20 @@ def __init__(self, project, text_min_length=500, sentence_min_length=50):
         super().__init__(project)
         self.text_min_length = int(text_min_length)
         self.sentence_min_length = int(sentence_min_length)
+        self.detector = (
+            lingua.LanguageDetectorBuilder
+            .from_all_languages()
+            .with_low_accuracy_mode()
+            .build()
+        )
 
     def _detect_language(self, text):
         """Tries to detect the language of a text input. Outputs a BCP-47-style
         language code (e.g. 'en')."""
 
-        lan_info = cld3.get_language(text)
-        if lan_info is not None and lan_info.is_reliable:
-            return lan_info.language
+        lan_info = self.detector.detect_language_of(text)
+        if lan_info is not None:
+            return lan_info.iso_code_639_1.name.lower()
         else:
             return None
 

pyproject.toml

@@ -56,7 +56,7 @@ tensorflow-cpu = {version = "2.9.1", optional = true}
 lmdb = {version = "1.3.0", optional = true}
 omikuji = {version = "0.5.*", optional = true}
 yake = {version = "0.4.5", optional = true}
-pycld3 = {version = "*", optional = true}
+lingua-language-detector = {version = "1.1.1", optional = true}
 spacy = {version = "3.3.*", optional = true}
 
 [tool.poetry.dev-dependencies]
@@ -79,7 +79,7 @@ voikko = ["voikko"]
 nn = ["tensorflow-cpu", "lmdb"]
 omikuji = ["omikuji"]
 yake = ["yake"]
-pycld3 = ["pycld3"]
+lingua = ["lingua-language-detector"]
 spacy = ["spacy"]
 
 [tool.poetry.scripts]

tests/test_transform_langfilter.py

@@ -32,7 +32,6 @@ def test_lang_filter(project):
         Kansalliskirjasto on kaikille avoin kulttuuriperintöorganisaatio, joka
         palvelee valtakunnallisesti kansalaisia, tiedeyhteisöjä ja muita
         yhteiskunnan toimijoita.
-        Abc defghij klmnopqr stuwxyz abc defghij klmnopqr stuwxyz.
         Turvaamme Suomessa julkaistun tai Suomea koskevan julkaistun
         kulttuuriperinnön saatavuuden sekä välittämme ja tuotamme
         tietosisältöjä tutkimukselle, opiskelulle, kansalaisille ja