fix: allow to update individual screenshots

src/Mixins/Expectation.php

@@ -14,6 +14,7 @@ use InvalidArgumentException;
 use JsonSerializable;
 use Pest\Exceptions\InvalidExpectationValue;
 use Pest\Matchers\Any;
+use Pest\Plugins\Snapshot;
 use Pest\Support\Arr;
 use Pest\Support\Exporter;
 use Pest\Support\NullClosure;
@@ -851,18 +852,31 @@ final class Expectation
             default => InvalidExpectationValue::expected('array|object|string'),
         };
 
-        if ($snapshots->has()) {
+        if (! $snapshots->has()) {
-            [$filename, $content] = $snapshots->get();
-
-            Assert::assertSame(
-                strtr($content, ["\r\n" => "\n", "\r" => "\n"]),
-                strtr($string, ["\r\n" => "\n", "\r" => "\n"]),
-                $message === '' ? "Failed asserting that the string value matches its snapshot ($filename)." : $message
-            );
-        } else {
             $filename = $snapshots->save($string);
 
             TestSuite::getInstance()->registerSnapshotChange("Snapshot created at [$filename]");
+        } else {
+            [$filename, $content] = $snapshots->get();
+
+            $normalizedContent = strtr($content, ["\r\n" => "\n", "\r" => "\n"]);
+            $normalizedString = strtr($string, ["\r\n" => "\n", "\r" => "\n"]);
+
+            if (Snapshot::$updateSnapshots && $normalizedContent !== $normalizedString) {
+                $snapshots->save($string);
+
+                TestSuite::getInstance()->registerSnapshotChange("Snapshot updated at [$filename]");
+            } else {
+                if (Snapshot::$updateSnapshots) {
+                    TestSuite::getInstance()->registerSnapshotChange("Snapshot unchanged at [$filename]");
+                }
+
+                Assert::assertSame(
+                    $normalizedContent,
+                    $normalizedString,
+                    $message === '' ? "Failed asserting that the string value matches its snapshot ($filename)." : $message
+                );
+            }
         }
 
         return $this;

src/Plugins/Snapshot.php

@@ -14,12 +14,19 @@ final class Snapshot implements HandlesArguments
 {
     use Concerns\HandleArguments;
 
+    /**
+     * Whether snapshots should be updated on this run.
+     */
+    public static bool $updateSnapshots = false;
+
     /**
      * {@inheritDoc}
      */
     public function handleArguments(array $arguments): array
     {
-        if (Parallel::isWorker()) {
+        if (Parallel::isWorker() && Parallel::getGlobal('UPDATE_SNAPSHOTS') === true) {
+            self::$updateSnapshots = true;
+
             return $arguments;
         }
 
@@ -27,8 +34,96 @@ final class Snapshot implements HandlesArguments
             return $arguments;
         }
 
-        TestSuite::getInstance()->snapshots->flush();
+        self::$updateSnapshots = true;
+
+        if ($this->isFullRun($arguments)) {
+            TestSuite::getInstance()->snapshots->flush();
+        }
+
+        if ($this->hasArgument('--parallel', $arguments) || $this->hasArgument('-p', $arguments)) {
+            Parallel::setGlobal('UPDATE_SNAPSHOTS', true);
+        }
 
         return $this->popArgument('--update-snapshots', $arguments);
     }
+
+    /**
+     * Options that take a value as the next argument (rather than via "=value").
+     *
+     * @var list<string>
+     */
+    private const array FLAGS_WITH_VALUES = [
+        '--filter',
+        '--group',
+        '--exclude-group',
+        '--test-suffix',
+        '--covers',
+        '--uses',
+        '--cache-directory',
+        '--cache-result-file',
+        '--configuration',
+        '--colors',
+        '--test-directory',
+        '--bootstrap',
+        '--order-by',
+        '--random-order-seed',
+        '--log-junit',
+        '--log-teamcity',
+        '--log-events-text',
+        '--log-events-verbose-text',
+        '--coverage-clover',
+        '--coverage-cobertura',
+        '--coverage-crap4j',
+        '--coverage-html',
+        '--coverage-php',
+        '--coverage-text',
+        '--coverage-xml',
+        '--assignee',
+        '--issue',
+        '--ticket',
+        '--pr',
+        '--pull-request',
+        '--retry',
+        '--shard',
+        '--repeat',
+    ];
+
+    /**
+     * Determines whether the command targets the entire suite (no filter, no path).
+     *
+     * @param  array<int, string>  $arguments
+     */
+    private function isFullRun(array $arguments): bool
+    {
+        if ($this->hasArgument('--filter', $arguments)) {
+            return false;
+        }
+
+        $tokens = array_slice($arguments, 1);
+        $skipNext = false;
+
+        foreach ($tokens as $arg) {
+            if ($skipNext) {
+                $skipNext = false;
+
+                continue;
+            }
+
+            if ($arg === '') {
+                continue;
+            }
+
+            if ($arg[0] === '-') {
+                if (in_array($arg, self::FLAGS_WITH_VALUES, true)) {
+                    $skipNext = true;
+                }
+
+                continue;
+            }
+
+            return false;
+        }
+
+        return true;
+    }
 }