Metadata length validation: count graphemes instead of unicode code p…

…oints

pyproject.toml

@@ -18,6 +18,10 @@ dependencies = [
   "beautifulsoup4>=4.9.3,<5.0",
   "lxml>=4.6.3,<6.0",
   "optimize-images>=1.3.6,<2.0",
+  # regex has nNo upper-bound due to "date-based" release numbers, no semver, so their
+  # promise is that they will never (or always) break the API, and the API is very
+  # limited and we use only a very small subset of it.
+  "regex>=2020.7.14",
   # youtube-dl should be updated as frequently as possible
   "yt-dlp"
 ]

src/zimscraperlib/zim/metadata.py

@@ -5,6 +5,8 @@
 from collections.abc import Iterable
 from typing import Any
 
+import regex
+
 from zimscraperlib.constants import (
     ILLUSTRATIONS_METADATA_RE,
     MANDATORY_ZIM_METADATA_KEYS,
@@ -16,6 +18,11 @@
 from zimscraperlib.image.probing import is_valid_image
 
 
+def nb_grapheme_for(value: str) -> int:
+    """Number of graphemes (visually perceived characters) in a given string"""
+    return len(regex.findall(r"\X", value))
+
+
 def validate_required_values(name: str, value: Any):
     """ensures required ones have a value (spec doesnt requires it but makes sense)"""
     if name in MANDATORY_ZIM_METADATA_KEYS and not value:
@@ -43,7 +50,7 @@ def validate_standard_str_types(name: str, value: str):
 
 def validate_title(name: str, value: str):
     """ensures Title metadata is within recommended length"""
-    if name == "Title" and len(value) > RECOMMENDED_MAX_TITLE_LENGTH:
+    if name == "Title" and nb_grapheme_for(value) > RECOMMENDED_MAX_TITLE_LENGTH:
         raise ValueError(f"{name} is too long.")
 
 
@@ -83,15 +90,18 @@ def validate_counter(name: str, value: str):  # noqa: ARG001
 
 def validate_description(name: str, value: str):
     """ensures Description metadata is with required length"""
-    if name == "Description" and len(value) > MAXIMUM_DESCRIPTION_METADATA_LENGTH:
+    if (
+        name == "Description"
+        and nb_grapheme_for(value) > MAXIMUM_DESCRIPTION_METADATA_LENGTH
+    ):
         raise ValueError(f"{name} is too long.")
 
 
 def validate_longdescription(name: str, value: str):
     """ensures LongDescription metadata is with required length"""
     if (
         name == "LongDescription"
-        and len(value) > MAXIMUM_LONG_DESCRIPTION_METADATA_LENGTH
+        and nb_grapheme_for(value) > MAXIMUM_LONG_DESCRIPTION_METADATA_LENGTH
     ):
         raise ValueError(f"{name} is too long.")
 

tests/zim/test_zim_creator.py

@@ -739,7 +739,7 @@ def test_config_metadata(tmp_path, png_image, tags):
         ("Flavour", 4, False),
         ("Source", 4, False),
         ("Scraper", 4, False),
-        ("Title", "X" * 30, True),
+        ("Title", "में" * 30, True),
         ("Title", "X" * 31, False),
         ("Date", 4, False),
         ("Date", datetime.datetime.now(), True),  # noqa: DTZ005
@@ -762,9 +762,9 @@ def test_config_metadata(tmp_path, png_image, tags):
         ("Language", "eng,", False),
         ("Language", "eng, fra", False),
         ("Counter", "1", False),
-        ("Description", "X" * 80, True),
+        ("Description", "में" * 80, True),
         ("Description", "X" * 81, False),
-        ("LongDescription", "X" * 4000, True),
+        ("LongDescription", "में" * 4000, True),
         ("LongDescription", "X" * 4001, False),
         ("Tags", 4, False),
         ("Tags", ["wikipedia", 4, "football"], False),