Relax JSON schema inference generics (#4063)

* Relax JSON schema inference generics

* Clippy

arrow-json/src/reader/schema.rs

@@ -20,7 +20,7 @@ use indexmap::map::IndexMap as HashMap;
 use indexmap::set::IndexSet as HashSet;
 use serde_json::Value;
 use std::borrow::Borrow;
-use std::io::{BufRead, BufReader, Read, Seek};
+use std::io::{BufRead, Seek};
 use std::sync::Arc;
 
 #[derive(Debug, Clone)]
@@ -147,17 +147,17 @@ fn generate_schema(spec: HashMap<String, InferredType>) -> Result<Schema, ArrowE
 /// }
 /// ```
 #[derive(Debug)]
-pub struct ValueIter<'a, R: Read> {
-    reader: &'a mut BufReader<R>,
+pub struct ValueIter<R: BufRead> {
+    reader: R,
     max_read_records: Option<usize>,
     record_count: usize,
     // reuse line buffer to avoid allocation on each record
     line_buf: String,
 }
 
-impl<'a, R: Read> ValueIter<'a, R> {
+impl<R: BufRead> ValueIter<R> {
     /// Creates a new `ValueIter`
-    pub fn new(reader: &'a mut BufReader<R>, max_read_records: Option<usize>) -> Self {
+    pub fn new(reader: R, max_read_records: Option<usize>) -> Self {
         Self {
             reader,
             max_read_records,
@@ -167,7 +167,7 @@ impl<'a, R: Read> ValueIter<'a, R> {
     }
 }
 
-impl<'a, R: Read> Iterator for ValueIter<'a, R> {
+impl<R: BufRead> Iterator for ValueIter<R> {
     type Item = Result<Value, ArrowError>;
 
     fn next(&mut self) -> Option<Self::Item> {
@@ -228,11 +228,11 @@ impl<'a, R: Read> Iterator for ValueIter<'a, R> {
 /// ```
 ///
 /// [`Reader`]: super::Reader
-pub fn infer_json_schema_from_seekable<R: Read + Seek>(
-    reader: &mut BufReader<R>,
+pub fn infer_json_schema_from_seekable<R: BufRead + Seek>(
+    mut reader: R,
     max_read_records: Option<usize>,
 ) -> Result<Schema, ArrowError> {
-    let schema = infer_json_schema(reader, max_read_records);
+    let schema = infer_json_schema(&mut reader, max_read_records);
     // return the reader seek back to the start
     reader.rewind()?;
 
@@ -265,8 +265,8 @@ pub fn infer_json_schema_from_seekable<R: Read + Seek>(
 /// // seek back to start so that the original file is usable again
 /// file.seek(SeekFrom::Start(0)).unwrap();
 /// ```
-pub fn infer_json_schema<R: Read>(
-    reader: &mut BufReader<R>,
+pub fn infer_json_schema<R: BufRead>(
+    reader: R,
     max_read_records: Option<usize>,
 ) -> Result<Schema, ArrowError> {
     infer_json_schema_from_iterator(ValueIter::new(reader, max_read_records))
@@ -515,7 +515,7 @@ mod tests {
     use super::*;
     use flate2::read::GzDecoder;
     use std::fs::File;
-    use std::io::Cursor;
+    use std::io::{BufReader, Cursor};
 
     #[test]
     fn test_json_infer_schema() {
@@ -700,8 +700,7 @@ mod tests {
 
     #[test]
     fn test_invalid_json_infer_schema() {
-        let re =
-            infer_json_schema_from_seekable(&mut BufReader::new(Cursor::new(b"}")), None);
+        let re = infer_json_schema_from_seekable(Cursor::new(b"}"), None);
         assert_eq!(
             re.err().unwrap().to_string(),
             "Json error: Not valid JSON: expected value at line 1 column 1",