Tidy up CSV encoding detection (#47809)

deps.edn

@@ -36,6 +36,7 @@
                                              :exclusions  [it.unimi.dsi/fastutil
                                                            org.slf4j/slf4j-api]}
   com.draines/postal                        {:mvn/version "2.0.5"}              ; SMTP library
+  ; Detect the charset in uploaded CSV files
   com.github.albfernandez/juniversalchardet {:mvn/version "2.5.0"}
   com.github.seancorfield/honeysql          {:mvn/version "2.6.1126"}           ; Honey SQL 2. SQL generation from Clojure data maps
   com.github.seancorfield/next.jdbc         {:mvn/version "1.3.925"}            ; Talk to JDBC DBs

src/metabase/upload.clj

@@ -291,16 +291,14 @@
             (if (pos? bytes-read)
               (do
                 (.handleData detector buffer 0 bytes-read)
-                (if (.isDone detector)
-                  (.getDetectedCharset detector)
+                (when-not (.isDone detector)
                   (recur)))
-              (do
-                (.dataEnd detector)
-                (.getDetectedCharset detector)))))))
+              (.dataEnd detector)))))
+      (.getDetectedCharset detector))
     (catch Exception _)))
 
 (defn- ->reader ^Reader [^File file]
-  ;; Just live with unrecognized characters
+  ;; If we can't detect the encoding, just live with unrecognized characters.
   (let [charset (or (detect-charset file) "UTF-8")]
     (-> (bom/bom-input-stream file)
         (InputStreamReader. charset))))