Adding Statement::select method

CHANGELOG.md

@@ -2,6 +2,24 @@
 
 All Notable changes to `Csv` will be documented in this file
 
+## [Next](https://github.com/thephpleague/csv/compare/9.14.0...master) - TBD
+
+### Added
+
+- `Statement::select`
+
+### Deprecated
+
+- None
+
+### Fixed
+
+- `Reader::select` and `ResultSet::select` now internally use `Statement::select`
+
+### Removed
+
+- None
+
 ## [9.14.0](https://github.com/thephpleague/csv/compare/9.13.0...9.14.0) - 2023-12-29
 
 ### Added

docs/9.0/reader/statement.md

@@ -107,6 +107,26 @@ $records = Statement::create()
 
 <p class="message-notice">When called multiple times, each call overrides the last setting for these options.</p>
 
+### Selecting columns
+
+<p class="message-info">new in version <code>9.15.0</code>.</p>
+
+You may not always want to select all columns from the tabular data. Using the `select` method,
+you can specify which columns to use. The column can be specified by their name, if the instance
+`getHeader` returns a non-empty array, or you can default to using the column offset. You
+can even mix them both.
+
+```php
+use League\Csv\Reader;
+use League\Csv\Statement;
+
+$reader = Reader::createFromPath('/path/to/file.csv');
+$records = Statement::create()
+    ->select(1, 3, 'field')
+    ->process($reader);
+// $records is a League\Csv\ResultSet instance with only 3 fields
+```
+
 ## FragmentFinder
 
 <p class="message-info">This mechanism is introduced with version <code>9.12.0</code>.</p>

docs/9.0/reader/tabular-data-reader.md

@@ -447,6 +447,7 @@ $reader = Reader::createFromPath('/path/to/my/file.csv')
 ```
 
 <p class="message-notice">Added in version <code>9.12.0</code> for <code>Reader</code> and <code>ResultSet</code>.</p>
+<p class="message-info"> Wraps the functionality of <code>Statement::select</code>.</p>
 
 ### matching, matchingFirst, matchingFirstOrFail
 

src/Reader.php

@@ -395,7 +395,7 @@ public function matchingFirstOrFail(string $expression): TabularDataReader
 
     public function select(string|int ...$columns): TabularDataReader
     {
-        return ResultSet::createFromTabularDataReader($this)->select(...$columns);
+        return Statement::create()->select(...$columns)->process($this);
     }
 
     /**

src/ResultSet.php

@@ -177,35 +177,7 @@ public function sorted(Closure $orderBy): TabularDataReader
 
     public function select(string|int ...$columns): TabularDataReader
     {
-        $header = [];
-        $documentHeader = $this->getHeader();
-        $hasNoHeader = [] === $documentHeader;
-        foreach ($columns as $field) {
-            if (is_string($field)) {
-                if ($hasNoHeader) {
-                    throw new InvalidArgument(__METHOD__.' can only use named column if the tabular data has a non-empty header.');
-                }
-
-                $index = array_search($field, $this->header, true);
-                if (false === $index) {
-                    throw InvalidArgument::dueToInvalidColumnIndex($field, 'offset', __METHOD__);
-                }
-
-                $header[$index] = $field;
-                continue;
-            }
-
-            if (!$hasNoHeader && !array_key_exists($field, $documentHeader)) {
-                throw InvalidArgument::dueToInvalidColumnIndex($field, 'offset', __METHOD__);
-            }
-
-            $header[$field] = $documentHeader[$field] ?? $field;
-        }
-
-        /** @var array<int, string> $finalHeader */
-        $finalHeader = $hasNoHeader ? [] : $header;
-
-        return new self($this->combineHeader($header), $finalHeader);
+        return Statement::create()->select(...$columns)->process($this);
     }
 
     public function matching(string $expression): iterable

src/Serializer/CastToEnum.php

@@ -86,7 +86,7 @@ private function cast(string $value): BackedEnum|UnitEnum
                 return $enum->getCase($value)->getValue();
             }
 
-            $backedValue = 'int' === $enum->getBackingType()?->getName() ? filter_var($value, Type::Int->filterFlag()) : $value;
+            $backedValue = 'int' === $enum->getBackingType()->getName() ? filter_var($value, Type::Int->filterFlag()) : $value;
 
             return $this->class::from($backedValue); /* @phpstan-ignore-line */
         } catch (Throwable $exception) {

src/Statement.php

@@ -18,7 +18,12 @@
 use Iterator;
 use LimitIterator;
 
+use function array_key_exists;
 use function array_reduce;
+use function array_search;
+use function array_values;
+use function is_string;
+use function trigger_error;
 
 use const E_USER_DEPRECATED;
 
@@ -35,6 +40,8 @@ class Statement
     protected int $offset = 0;
     /** iterator maximum length. */
     protected int $limit = -1;
+    /** @var array<string|int> */
+    protected array $select = [];
 
     /**
      * @throws Exception
@@ -49,6 +56,21 @@ public static function create(callable $where = null, int $offset = 0, int $limi
         return $stmt->offset($offset)->limit($limit);
     }
 
+    /**
+     * Sets the Iterator element columns.
+     */
+    public function select(string|int ...$columns): self
+    {
+        if ($columns === $this->select) {
+            return $this;
+        }
+
+        $clone = clone $this;
+        $clone->select = $columns;
+
+        return $clone;
+    }
+
     /**
      * Sets the Iterator filter method.
      */
@@ -118,6 +140,7 @@ public function limit(int $limit): self
      *
      * @param array<string> $header an optional header to use instead of the CSV document header
      *
+     * @throws InvalidArgument
      * @throws SyntaxError
      */
     public function process(TabularDataReader $tabular_data, array $header = []): TabularDataReader
@@ -136,7 +159,7 @@ public function process(TabularDataReader $tabular_data, array $header = []): Ta
         /** @var Iterator<array-key, array<array-key, string|null>> $iterator */
         $iterator = new LimitIterator($iterator, $this->offset, $this->limit);
 
-        return new ResultSet($iterator, $header);
+        return $this->applySelect($iterator, $header);
     }
 
     /**
@@ -172,4 +195,52 @@ protected function buildOrderBy(Iterator $iterator): Iterator
 
         return $it;
     }
+
+    /**
+     *
+     * @throws InvalidArgument
+     * @throws SyntaxError
+     */
+    protected function applySelect(Iterator $records, array $recordsHeader): TabularDataReader
+    {
+        if ([] === $this->select) {
+            return new ResultSet($records, $recordsHeader);
+        }
+
+        $hasHeader = [] !== $recordsHeader;
+        $selectColumn = function (array $header, string|int $field) use ($recordsHeader, $hasHeader): array {
+            if (is_string($field)) {
+                $index = array_search($field, $recordsHeader, true);
+                if (false === $index) {
+                    throw InvalidArgument::dueToInvalidColumnIndex($field, 'offset', __METHOD__);
+                }
+
+                $header[$index] = $field;
+
+                return $header;
+            }
+
+            if ($hasHeader && !array_key_exists($field, $recordsHeader)) {
+                throw InvalidArgument::dueToInvalidColumnIndex($field, 'offset', __METHOD__);
+            }
+
+            $header[$field] = $recordsHeader[$field] ?? $field;
+
+            return $header;
+        };
+
+        /** @var array<string> $header */
+        $header = array_reduce($this->select, $selectColumn, []);
+        $records = new MapIterator($records, function (array $record) use ($header): array {
+            $element = [];
+            $row = array_values($record);
+            foreach ($header as $offset => $headerName) {
+                $element[$headerName] = $row[$offset] ?? null;
+            }
+
+            return $element;
+        });
+
+        return new ResultSet($records, $hasHeader ? $header : []);
+    }
 }