AVRO-4298: [php] Restore original AVRO_MAX_COLLECTION_ITEMS in tests

Addresses review feedback: the collection-limit tests unconditionally unset
AVRO_MAX_COLLECTION_ITEMS in their finally blocks, breaking isolation when the
variable is already set in the environment (CI or a developer shell). Capture
the pre-existing value in setUp() and restore it via a helper in each finally
block instead of blindly unsetting.

Assisted-by: GitHub Copilot:claude-opus-4.8

Author: iemejia

lang/php/test/DatumIOTest.php

@@ -35,6 +35,19 @@
 
 class DatumIOTest extends TestCase
 {
+    /** @var false|string Value of AVRO_MAX_COLLECTION_ITEMS captured before each test. */
+    private string|false $originalMaxCollectionItems = false;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+        // Capture any pre-existing value so tests that override
+        // AVRO_MAX_COLLECTION_ITEMS restore it rather than unconditionally
+        // unsetting it, which would break isolation when the variable is already
+        // set in the environment (CI or a developer shell).
+        $this->originalMaxCollectionItems = getenv('AVRO_MAX_COLLECTION_ITEMS');
+    }
+
     #[DataProvider('data_provider')]
     public function test_datum_round_trip(string $schema_json, mixed $datum, string $binary): void
     {
@@ -349,7 +362,7 @@ public function test_array_of_null_within_configured_limit_still_reads(): void
             $result = $this->decodeWith('{"type":"array","items":"null"}', self::zeroByteBlock(1000));
             $this->assertCount(1000, $result);
         } finally {
-            putenv('AVRO_MAX_COLLECTION_ITEMS');
+            $this->restoreMaxCollectionItems();
         }
     }
 
@@ -361,7 +374,7 @@ public function test_array_of_null_exceeds_configured_limit(): void
             $this->expectException(AvroIOCollectionSizeException::class);
             $this->decodeWith('{"type":"array","items":"null"}', self::zeroByteBlock(1001));
         } finally {
-            putenv('AVRO_MAX_COLLECTION_ITEMS');
+            $this->restoreMaxCollectionItems();
         }
     }
 
@@ -378,7 +391,7 @@ public function test_array_of_null_cumulative_across_blocks(): void
             $this->expectException(AvroIOCollectionSizeException::class);
             $this->decodeWith('{"type":"array","items":"null"}', $io);
         } finally {
-            putenv('AVRO_MAX_COLLECTION_ITEMS');
+            $this->restoreMaxCollectionItems();
         }
     }
 
@@ -390,7 +403,7 @@ public function test_array_of_null_negative_block_count(): void
             $this->expectException(AvroIOCollectionSizeException::class);
             $this->decodeWith('{"type":"array","items":"null"}', self::zeroByteBlock(200000, true));
         } finally {
-            putenv('AVRO_MAX_COLLECTION_ITEMS');
+            $this->restoreMaxCollectionItems();
         }
     }
 
@@ -413,7 +426,7 @@ public function test_map_cumulative_limit_not_bypassed_by_duplicate_keys(): void
             $this->expectException(AvroIOCollectionSizeException::class);
             $this->decodeWith('{"type":"map","values":"null"}', $io);
         } finally {
-            putenv('AVRO_MAX_COLLECTION_ITEMS');
+            $this->restoreMaxCollectionItems();
         }
     }
 
@@ -425,7 +438,7 @@ public function test_array_of_zero_length_fixed_exceeds_limit(): void
             $this->expectException(AvroIOCollectionSizeException::class);
             $this->decodeWith('{"type":"array","items":{"type":"fixed","name":"empty","size":0}}', self::zeroByteBlock(2000));
         } finally {
-            putenv('AVRO_MAX_COLLECTION_ITEMS');
+            $this->restoreMaxCollectionItems();
         }
     }
 
@@ -440,7 +453,7 @@ public function test_array_of_all_null_record_exceeds_limit(): void
                 self::zeroByteBlock(2000)
             );
         } finally {
-            putenv('AVRO_MAX_COLLECTION_ITEMS');
+            $this->restoreMaxCollectionItems();
         }
     }
 
@@ -462,7 +475,7 @@ public function test_invalid_env_override_falls_back_to_default(): void
             $this->expectException(AvroIOCollectionSizeException::class);
             $this->decodeWith('{"type":"array","items":"null"}', self::zeroByteBlock(200000000));
         } finally {
-            putenv('AVRO_MAX_COLLECTION_ITEMS');
+            $this->restoreMaxCollectionItems();
         }
     }
 
@@ -475,7 +488,7 @@ public function test_env_override_raises_limit(): void
             $result = $this->decodeWith('{"type":"array","items":"null"}', self::zeroByteBlock(15000));
             $this->assertCount(15000, $result);
         } finally {
-            putenv('AVRO_MAX_COLLECTION_ITEMS');
+            $this->restoreMaxCollectionItems();
         }
     }
 
@@ -496,7 +509,7 @@ public function test_non_zero_collection_bounded_by_structural_cap(): void
             $this->expectException(AvroIOCollectionSizeException::class);
             $this->decodeWith('{"type":"array","items":"long"}', $io);
         } finally {
-            putenv('AVRO_MAX_COLLECTION_ITEMS');
+            $this->restoreMaxCollectionItems();
         }
     }
 
@@ -512,7 +525,7 @@ public function test_skip_array_of_null_respects_limit(): void
             $this->expectException(AvroIOCollectionSizeException::class);
             AvroIODatumReader::skipData($schema, new AvroIOBinaryDecoder($io));
         } finally {
-            putenv('AVRO_MAX_COLLECTION_ITEMS');
+            $this->restoreMaxCollectionItems();
         }
     }
 
@@ -529,7 +542,7 @@ public function test_skip_array_of_null_negative_block_respects_limit(): void
             $this->expectException(AvroIOCollectionSizeException::class);
             AvroIODatumReader::skipData($schema, new AvroIOBinaryDecoder($io));
         } finally {
-            putenv('AVRO_MAX_COLLECTION_ITEMS');
+            $this->restoreMaxCollectionItems();
         }
     }
 
@@ -692,6 +705,15 @@ public function test_field_default_value(
         }
     }
 
+    protected function restoreMaxCollectionItems(): void
+    {
+        if (false === $this->originalMaxCollectionItems) {
+            putenv('AVRO_MAX_COLLECTION_ITEMS');
+        } else {
+            putenv('AVRO_MAX_COLLECTION_ITEMS='.$this->originalMaxCollectionItems);
+        }
+    }
+
     /**
      * Builds one array/map block of `$count` zero-byte elements plus an end
      * marker (a negative count is preceded by a block byte-size).