fix(pipeline): decode GIAS extracts as Windows-1252

GIAS publishes its CSVs in Windows-1252 and sends no charset. The tap read
resp.text, so requests guessed the codec, and the encoding="latin-1" passed
to read_csv did nothing on already-decoded text. On 3 Oct 2026 the guess was
windows-1250, and "St Thomas à Becket" (138950, 149557) was stored as
"St Thomas ŕ Becket". A different guess on another day would garble other
accented names.

Both streams now decode the downloaded bytes themselves (gias_csv.py). A byte
Windows-1252 leaves undefined becomes U+FFFD with a logged warning instead of
failing the load, so one odd name cannot stop the daily refresh. None of the
nine extracts checked (1 Jul to 3 Oct 2026) contains such a byte.

Checked by running the tap on the real 3 Oct extract with .text forced to
windows-1250: all 52,586 rows decode, with no "ŕ" and no replacement
characters.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

pipeline/plugins/extractors/tap-uk-gias/tap_uk_gias/gias_csv.py

@@ -0,0 +1,26 @@
+"""Read a GIAS extract from the raw bytes of the download.
+
+GIAS writes its CSVs in Windows-1252 and sends no charset, so `resp.text`
+leaves requests to guess the codec. On 3 Oct 2026 it guessed windows-1250 and
+"à" became "ŕ". Decode the bytes ourselves instead.
+"""
+
+from __future__ import annotations
+
+import io
+
+import pandas as pd
+
+GIAS_ENCODING = "cp1252"
+
+
+def read_gias_csv(content: bytes, logger=None) -> pd.DataFrame:
+    """Every column as a string; a blank cell stays ''."""
+    # Windows-1252 leaves five bytes undefined. One stray byte must not stop
+    # the daily refresh of every school, so it becomes U+FFFD and is logged.
+    text = content.decode(GIAS_ENCODING, errors="replace")
+    undecodable = text.count("�")
+    if undecodable and logger is not None:
+        logger.warning("%d byte(s) in the GIAS extract could not be decoded as %s",
+                       undecodable, GIAS_ENCODING)
+    return pd.read_csv(io.StringIO(text), dtype=str, keep_default_na=False)

pipeline/plugins/extractors/tap-uk-gias/tap_uk_gias/tap.py

@@ -7,6 +7,8 @@ from datetime import date, timedelta
 from singer_sdk import Stream, Tap
 from singer_sdk import typing as th
 
+from tap_uk_gias.gias_csv import read_gias_csv
+
 GIAS_URL_TEMPLATE = (
     "https://ea-edubase-api-prod.azurewebsites.net"
     "/edubase/downloads/public/edubasealldata{date}.csv"
@@ -74,9 +76,6 @@ class GIASEstablishmentsStream(Stream):
 
     def get_records(self, context):
         """Download GIAS CSV and yield rows."""
-        import io
-
-        import pandas as pd
         import requests
 
         today = date.today()
@@ -94,12 +93,7 @@ class GIASEstablishmentsStream(Stream):
 
         resp.raise_for_status()
 
-        df = pd.read_csv(
-            io.StringIO(resp.text),
-            encoding="latin-1",
-            dtype=str,
-            keep_default_na=False,
-        )
+        df = read_gias_csv(resp.content, self.logger)
 
         for _, row in df.iterrows():
             record = row.to_dict()
@@ -126,9 +120,6 @@ class GIASLinksStream(Stream):
 
     def get_records(self, context):
         """Download GIAS links CSV and yield rows."""
-        import io
-
-        import pandas as pd
         import requests
 
         today = date.today()
@@ -146,12 +137,7 @@ class GIASLinksStream(Stream):
 
         resp.raise_for_status()
 
-        df = pd.read_csv(
-            io.StringIO(resp.text),
-            encoding="latin-1",
-            dtype=str,
-            keep_default_na=False,
-        )
+        df = read_gias_csv(resp.content, self.logger)
 
         for _, row in df.iterrows():
             record = row.to_dict()