ARROW-9192: [CI][Rust] Add support for running clippy

The goal of this PR is not to fix all the clippy errors/warnings in arrow crate, but to make sure no new linting errors are introduced in the future so we can slowly fix the remaining errors.

Closes #7501 from houqp/ARROW-9192

Lead-authored-by: Qingping Hou <dave2008713@gmail.com>
Co-authored-by: Krisztián Szűcs <szucs.krisztian@gmail.com>
Signed-off-by: Krisztián Szűcs <szucs.krisztian@gmail.com>

.github/workflows/rust.yml

@@ -127,7 +127,7 @@ jobs:
         with:
           toolchain: ${{ matrix.rust }}
           override: true
-          components: rustfmt
+          components: rustfmt, clippy
       - name: Install Flatbuffers
         shell: bash
         run: brew install flatbuffers
@@ -138,6 +138,9 @@ jobs:
       - name: Fetch Submodules and Tags
         shell: bash
         run: ci/scripts/util_checkout.sh
+      - name: Run Clippy
+        shell: bash
+        run: ci/scripts/rust_lint.sh $(pwd)
       - name: Build
         shell: bash
         run: ci/scripts/rust_build.sh $(pwd) $(pwd)/build

ci/scripts/rust_lint.sh

@@ -0,0 +1,41 @@
+#!/usr/bin/env bash
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+set -e
+
+source_dir=${1}/rust
+
+pushd ${source_dir}
+    max_error_cnt=3
+    max_warn_cnt=9
+
+    error_msg=$(cargo clippy -- -A clippy::redundant_field_names 2>&1 | grep 'error: aborting due to')
+
+    error_cnt=$(echo "${error_msg}" | awk '{print $5}')
+    [[ ${error_cnt} -gt ${max_error_cnt} ]] && {
+        echo "More clippy errors introduced, got: ${error_cnt}, was: ${max_error_cnt}"
+        exit 1
+    }
+
+    warn_cnt=$(echo "${error_msg}" | awk '{print $8}')
+    [[ ${warn_cnt} -gt ${max_warn_cnt} ]] && {
+        echo "More clippy warnings introduced, got: ${warn_cnt}, was: ${max_warn_cnt}"
+        exit 1
+    }
+popd

rust/arrow/src/array/builder.rs

@@ -1143,7 +1143,7 @@ fn append_binary_data(
                     DataType::List(Box::new(DataType::UInt8)),
                     array.len(),
                     None,
-                    array.null_buffer().map(|buf| buf.clone()),
+                    array.null_buffer().cloned(),
                     array.offset(),
                     vec![(&array.buffers()[0]).clone()],
                     vec![int_data],
@@ -1195,7 +1195,7 @@ impl ArrayBuilder for FixedSizeBinaryBuilder {
                 DataType::FixedSizeList(Box::new(DataType::UInt8), self.builder.list_len),
                 array.len(),
                 None,
-                array.null_buffer().map(|buf| buf.clone()),
+                array.null_buffer().cloned(),
                 array.offset(),
                 vec![],
                 vec![int_data],

rust/arrow/src/array/data.rs

@@ -146,6 +146,10 @@ impl ArrayData {
         self.len
     }
 
+    pub fn is_empty(&self) -> bool {
+        self.len == 0
+    }
+
     /// Returns the offset of this array
     pub fn offset(&self) -> usize {
         self.offset

rust/arrow/src/array/mod.rs

@@ -81,6 +81,7 @@
 //! )
 //! ```
 
+#[allow(clippy::module_inception)]
 mod array;
 mod builder;
 mod cast;

rust/arrow/src/array/ord.rs

@@ -69,63 +69,61 @@ impl OrdArray for NullArray {
 }
 
 /// Convert ArrayRef to OrdArray trait object
-pub fn as_ordarray(values: &ArrayRef) -> Result<Box<&OrdArray>> {
+pub fn as_ordarray(values: &ArrayRef) -> Result<&OrdArray> {
     match values.data_type() {
-        DataType::Boolean => Ok(Box::new(as_boolean_array(&values))),
-        DataType::Utf8 => Ok(Box::new(as_string_array(&values))),
-        DataType::Null => Ok(Box::new(as_null_array(&values))),
-        DataType::Int8 => Ok(Box::new(as_primitive_array::<Int8Type>(&values))),
-        DataType::Int16 => Ok(Box::new(as_primitive_array::<Int16Type>(&values))),
-        DataType::Int32 => Ok(Box::new(as_primitive_array::<Int32Type>(&values))),
-        DataType::Int64 => Ok(Box::new(as_primitive_array::<Int64Type>(&values))),
-        DataType::UInt8 => Ok(Box::new(as_primitive_array::<UInt8Type>(&values))),
-        DataType::UInt16 => Ok(Box::new(as_primitive_array::<UInt16Type>(&values))),
-        DataType::UInt32 => Ok(Box::new(as_primitive_array::<UInt32Type>(&values))),
-        DataType::UInt64 => Ok(Box::new(as_primitive_array::<UInt64Type>(&values))),
-        DataType::Date32(_) => Ok(Box::new(as_primitive_array::<Date32Type>(&values))),
-        DataType::Date64(_) => Ok(Box::new(as_primitive_array::<Date64Type>(&values))),
-        DataType::Time32(Second) => {
-            Ok(Box::new(as_primitive_array::<Time32SecondType>(&values)))
+        DataType::Boolean => Ok(as_boolean_array(&values)),
+        DataType::Utf8 => Ok(as_string_array(&values)),
+        DataType::Null => Ok(as_null_array(&values)),
+        DataType::Int8 => Ok(as_primitive_array::<Int8Type>(&values)),
+        DataType::Int16 => Ok(as_primitive_array::<Int16Type>(&values)),
+        DataType::Int32 => Ok(as_primitive_array::<Int32Type>(&values)),
+        DataType::Int64 => Ok(as_primitive_array::<Int64Type>(&values)),
+        DataType::UInt8 => Ok(as_primitive_array::<UInt8Type>(&values)),
+        DataType::UInt16 => Ok(as_primitive_array::<UInt16Type>(&values)),
+        DataType::UInt32 => Ok(as_primitive_array::<UInt32Type>(&values)),
+        DataType::UInt64 => Ok(as_primitive_array::<UInt64Type>(&values)),
+        DataType::Date32(_) => Ok(as_primitive_array::<Date32Type>(&values)),
+        DataType::Date64(_) => Ok(as_primitive_array::<Date64Type>(&values)),
+        DataType::Time32(Second) => Ok(as_primitive_array::<Time32SecondType>(&values)),
+        DataType::Time32(Millisecond) => {
+            Ok(as_primitive_array::<Time32MillisecondType>(&values))
+        }
+        DataType::Time64(Microsecond) => {
+            Ok(as_primitive_array::<Time64MicrosecondType>(&values))
+        }
+        DataType::Time64(Nanosecond) => {
+            Ok(as_primitive_array::<Time64NanosecondType>(&values))
         }
-        DataType::Time32(Millisecond) => Ok(Box::new(as_primitive_array::<
-            Time32MillisecondType,
-        >(&values))),
-        DataType::Time64(Microsecond) => Ok(Box::new(as_primitive_array::<
-            Time64MicrosecondType,
-        >(&values))),
-        DataType::Time64(Nanosecond) => Ok(Box::new(as_primitive_array::<
-            Time64NanosecondType,
-        >(&values))),
         DataType::Timestamp(Second, _) => {
-            Ok(Box::new(as_primitive_array::<TimestampSecondType>(&values)))
+            Ok(as_primitive_array::<TimestampSecondType>(&values))
+        }
+        DataType::Timestamp(Millisecond, _) => {
+            Ok(as_primitive_array::<TimestampMillisecondType>(&values))
+        }
+        DataType::Timestamp(Microsecond, _) => {
+            Ok(as_primitive_array::<TimestampMicrosecondType>(&values))
+        }
+        DataType::Timestamp(Nanosecond, _) => {
+            Ok(as_primitive_array::<TimestampNanosecondType>(&values))
+        }
+        DataType::Interval(IntervalUnit::YearMonth) => {
+            Ok(as_primitive_array::<IntervalYearMonthType>(&values))
         }
-        DataType::Timestamp(Millisecond, _) => Ok(Box::new(as_primitive_array::<
-            TimestampMillisecondType,
-        >(&values))),
-        DataType::Timestamp(Microsecond, _) => Ok(Box::new(as_primitive_array::<
-            TimestampMicrosecondType,
-        >(&values))),
-        DataType::Timestamp(Nanosecond, _) => Ok(Box::new(as_primitive_array::<
-            TimestampNanosecondType,
-        >(&values))),
-        DataType::Interval(IntervalUnit::YearMonth) => Ok(Box::new(
-            as_primitive_array::<IntervalYearMonthType>(&values),
-        )),
         DataType::Interval(IntervalUnit::DayTime) => {
-            Ok(Box::new(as_primitive_array::<IntervalDayTimeType>(&values)))
+            Ok(as_primitive_array::<IntervalDayTimeType>(&values))
         }
         DataType::Duration(TimeUnit::Second) => {
-            Ok(Box::new(as_primitive_array::<DurationSecondType>(&values)))
+            Ok(as_primitive_array::<DurationSecondType>(&values))
+        }
+        DataType::Duration(TimeUnit::Millisecond) => {
+            Ok(as_primitive_array::<DurationMillisecondType>(&values))
+        }
+        DataType::Duration(TimeUnit::Microsecond) => {
+            Ok(as_primitive_array::<DurationMicrosecondType>(&values))
+        }
+        DataType::Duration(TimeUnit::Nanosecond) => {
+            Ok(as_primitive_array::<DurationNanosecondType>(&values))
         }
-        DataType::Duration(TimeUnit::Millisecond) => Ok(Box::new(as_primitive_array::<
-            DurationMillisecondType,
-        >(&values))),
-        DataType::Duration(TimeUnit::Microsecond) => Ok(Box::new(as_primitive_array::<
-            DurationMicrosecondType,
-        >(&values))),
-        DataType::Duration(TimeUnit::Nanosecond) => Ok(Box::new(as_primitive_array::<
-            DurationNanosecondType,
-        >(&values))),
         t => Err(ArrowError::ComputeError(format!(
             "Lexical Sort not supported for data type {:?}",
             t

rust/arrow/src/array/union.rs

@@ -172,7 +172,7 @@ impl UnionArray {
             .iter()
             .filter(|i| *i < &0)
             .collect::<Vec<&i8>>();
-        if invalid_type_ids.len() > 0 {
+        if !invalid_type_ids.is_empty() {
             return Err(ArrowError::InvalidArgumentError(format!(
                 "Type Ids must be positive and cannot be greater than the number of \
                 child arrays, found:\n{:?}",
@@ -188,7 +188,7 @@ impl UnionArray {
                 .iter()
                 .filter(|i| *i < &0 || *i > &max_len)
                 .collect::<Vec<&i32>>();
-            if invalid_offsets.len() > 0 {
+            if !invalid_offsets.is_empty() {
                 return Err(ArrowError::InvalidArgumentError(format!(
                     "Offsets must be positive and within the length of the Array, \
                     found:\n{:?}",
@@ -325,7 +325,7 @@ impl fmt::Debug for UnionArray {
                 column.data_type()
             )?;
             fmt::Debug::fmt(column, f)?;
-            writeln!(f, "")?;
+            writeln!(f)?;
         }
         writeln!(f, "]")
     }
@@ -484,7 +484,7 @@ impl UnionBuilder {
 
     /// Appends a null to this builder.
     pub fn append_null(&mut self) -> Result<()> {
-        if let None = self.bitmap_builder {
+        if self.bitmap_builder.is_none() {
             let mut builder = BooleanBufferBuilder::new(self.len + 1);
             for _ in 0..self.len {
                 builder.append(true)?;
@@ -499,7 +499,7 @@ impl UnionBuilder {
         self.type_id_builder.append(i8::default())?;
 
         // Handle sparse union
-        if let None = self.value_offset_builder {
+        if self.value_offset_builder.is_none() {
             for (_, fd) in self.fields.iter_mut() {
                 fd.append_null_dynamic()?;
             }
@@ -518,25 +518,22 @@ impl UnionBuilder {
 
         let mut field_data = match self.fields.remove(&type_name) {
             Some(data) => data,
-            None => {
-                let field_data = match self.value_offset_builder {
-                    Some(_) => {
-                        FieldData::new(self.fields.len() as i8, T::get_data_type(), None)
-                    }
-                    None => {
-                        let mut fd = FieldData::new(
-                            self.fields.len() as i8,
-                            T::get_data_type(),
-                            Some(BooleanBufferBuilder::new(1)),
-                        );
-                        for _ in 0..self.len {
-                            fd.append_null::<T>()?;
-                        }
-                        fd
+            None => match self.value_offset_builder {
+                Some(_) => {
+                    FieldData::new(self.fields.len() as i8, T::get_data_type(), None)
+                }
+                None => {
+                    let mut fd = FieldData::new(
+                        self.fields.len() as i8,
+                        T::get_data_type(),
+                        Some(BooleanBufferBuilder::new(1)),
+                    );
+                    for _ in 0..self.len {
+                        fd.append_null::<T>()?;
                     }
-                };
-                field_data
-            }
+                    fd
+                }
+            },
         };
         self.type_id_builder.append(field_data.type_id)?;
 

rust/arrow/src/bitmap.rs

@@ -51,6 +51,10 @@ impl Bitmap {
         self.bits.len()
     }
 
+    pub fn is_empty(&self) -> bool {
+        self.bits.is_empty()
+    }
+
     pub fn is_set(&self, i: usize) -> bool {
         assert!(i < (self.bits.len() << 3));
         unsafe { bit_util::get_bit_raw(self.bits.raw_data(), i) }
@@ -60,7 +64,7 @@ impl Bitmap {
         &self.bits
     }
 
-    pub fn to_buffer(self) -> Buffer {
+    pub fn into_buffer(self) -> Buffer {
         self.bits
     }
 }

rust/arrow/src/compute/kernels/sort.rs

@@ -271,7 +271,7 @@ pub fn lexsort_to_indices(columns: &Vec<SortColumn>) -> Result<UInt32Array> {
     // convert ArrayRefs to OrdArray trait objects and perform row count check
     let flat_columns = columns
         .iter()
-        .map(|column| -> Result<(Box<&OrdArray>, SortOptions)> {
+        .map(|column| -> Result<(&OrdArray, SortOptions)> {
             // row count check
             let curr_row_count = column.values.len() - column.values.offset();
             match row_count {
@@ -292,7 +292,7 @@ pub fn lexsort_to_indices(columns: &Vec<SortColumn>) -> Result<UInt32Array> {
                 column.options.unwrap_or_default(),
             ))
         })
-        .collect::<Result<Vec<(Box<&OrdArray>, SortOptions)>>>()?;
+        .collect::<Result<Vec<(&OrdArray, SortOptions)>>>()?;
 
     let lex_comparator = |a_idx: &usize, b_idx: &usize| -> Ordering {
         for column in flat_columns.iter() {

rust/arrow/src/csv/reader.rs

@@ -187,7 +187,7 @@ fn infer_file_schema<R: Read + Seek>(
 ///
 /// If `max_read_records` is not set, all files will be read fully to infer the schema.
 pub fn infer_schema_from_files(
-    files: &Vec<String>,
+    files: &[String],
     delimiter: u8,
     max_read_records: Option<usize>,
     has_header: bool,
@@ -207,7 +207,7 @@ pub fn infer_schema_from_files(
         }
         schemas.push(schema.clone());
         records_to_read -= records_read;
-        if records_to_read <= 0 {
+        if records_to_read == 0 {
             break;
         }
     }
@@ -283,11 +283,8 @@ impl<R: Read> Reader<R> {
         let mut reader_builder = csv_crate::ReaderBuilder::new();
         reader_builder.has_headers(has_header);
 
-        match delimiter {
-            Some(c) => {
-                reader_builder.delimiter(c);
-            }
-            _ => (),
+        if let Some(c) = delimiter {
+            reader_builder.delimiter(c);
         }
 
         let csv_reader = reader_builder.from_reader(buf_reader);
@@ -302,6 +299,7 @@ impl<R: Read> Reader<R> {
     }
 
     /// Read the next batch of rows
+    #[allow(clippy::should_implement_trait)]
     pub fn next(&mut self) -> Result<Option<RecordBatch>> {
         // read a batch of rows into memory
         let mut rows: Vec<StringRecord> = Vec::with_capacity(self.batch_size);