PHPStan Pro: analyse again the files changed while an analysis read them

src/Analyser/ResultCache/ResultCacheManager.php

@@ -1398,11 +1398,8 @@ public function process(AnalyserResult $analyserResult, ResultCache $resultCache
 
 			// The files changed during the analysis may have been read in another version than the one
 			// their hash and exported nodes describe, and so may the files using them, which are analysed
-			// again too. A run that analysed nothing read nothing.
-			$filesChangedDuringAnalysis = [];
-			if ($resultCache->isFullAnalysis() || $resultCache->getFilesToAnalyse() !== []) {
-				$filesChangedDuringAnalysis = $this->getFilesChangedSinceHashed($currentFileHashes);
-			}
+			// again too.
+			$filesChangedDuringAnalysis = $this->getFilesChangedDuringAnalysis($resultCache);
 			foreach (array_keys($filesChangedDuringAnalysis) as $file) {
 				if ($output->isVeryVerbose()) {
 					$output->writeLineFormatted(sprintf('Result cache will re-analyse %s and the files using it because it changed during the analysis.', $file));
@@ -3258,6 +3255,21 @@ private function fileStatSignaturesDiffer(array $cachedDependencies): bool
 		return false;
 	}
 
+	/**
+	 * The analysed files written to since restore() hashed them, for a result that may not describe
+	 * what they contain now. A run that analysed nothing read nothing.
+	 *
+	 * @return array<string, true>
+	 */
+	public function getFilesChangedDuringAnalysis(ResultCache $resultCache): array
+	{
+		if (!$resultCache->isFullAnalysis() && $resultCache->getFilesToAnalyse() === []) {
+			return [];
+		}
+
+		return $this->getFilesChangedSinceHashed($resultCache->getCurrentFileHashes());
+	}
+
 	/**
 	 * The analysed files written to after they were hashed. The analysis may have read them before
 	 * or after the write, or the files depending on them may have read the other version, so neither

src/Command/FixerApplication.php

@@ -75,6 +75,19 @@ final class FixerApplication
 	/** Files changed during the analysis in progress, another one starts once it ends. */
 	private bool $analysisRequested = false;
 
+	/**
+	 * The last analysis may have read files in another version than they have now. The file monitor
+	 * cannot tell when a file is back to the contents it last saw, like an edit undone between two polls.
+	 */
+	private bool $filesChangedWhileAnalysed = false;
+
+	/**
+	 * Nothing changed since the last analysis but the files it reported. Whatever writes to the
+	 * analysed files during every analysis, like a generator in a bootstrap file, would otherwise
+	 * keep the analyses going, so an analysis that was started for this cannot start another one.
+	 */
+	private bool $analysingOnlyFilesChangedWhileAnalysed = false;
+
 	private bool $fileMonitorActive = true;
 
 	/** @var string[] watched files besides the analysed ones and the config files */
@@ -431,7 +444,16 @@ private function monitorFileChanges(LoopInterface $loop, callable $hasChangesCal
 			$changes = $fileMonitor->getChanges();
 			$now = microtime(true);
 
+			// not during an analysis, the one starting after it might already be for something else
+			if ($this->filesChangedWhileAnalysed && $this->processInProgress === null) {
+				$this->filesChangedWhileAnalysed = false;
+				$this->analysingOnlyFilesChangedWhileAnalysed = true;
+				$firstChangeAt ??= $now;
+				$lastChangeAt = $now;
+			}
+
 			if ($changes->hasAnyChanges()) {
+				$this->analysingOnlyFilesChangedWhileAnalysed = false;
 				$firstChangeAt ??= $now;
 				$lastChangeAt = $now;
 				$hasChangesCallback($changes);
@@ -464,6 +486,9 @@ private function analyse(
 		Encoder $phpstanFixerEncoder,
 	): void
 	{
+		// this analysis reads the files as they are now
+		$this->filesChangedWhileAnalysed = false;
+
 		// TCP server for fixer:worker (TCP client)
 		$server = new TcpServer('127.0.0.1:0', $loop);
 		/** @var string $serverAddress */
@@ -486,6 +511,11 @@ private function analyse(
 					return;
 				}
 
+				if ($data['action'] === 'filesChangedWhileAnalysed') {
+					$this->filesChangedWhileAnalysed = !$this->analysingOnlyFilesChangedWhileAnalysed;
+					return;
+				}
+
 				$phpstanFixerEncoder->write($data);
 			});
 		});

src/Command/FixerWorkerRunner.php

@@ -232,6 +232,11 @@ function (array $errors, array $locallyIgnoredErrors, array $analysedFiles) use
 				$finalizerResult = $this->analyserResultFinalizer->finalize($resultCacheResult->getAnalyserResult(), $isOnlyFiles, false, null, null, $resultCache->getCollectedDataRuleResults());
 				$resultCacheResult->save($finalizerResult);
 
+				// FixerApplication's file monitor misses a file changed and changed back between two polls
+				if ($resultCacheManager->getFilesChangedDuringAnalysis($resultCache) !== []) {
+					$out->write(['action' => 'filesChangedWhileAnalysed', 'result' => []]);
+				}
+
 				$internalErrors = [];
 				foreach ($finalizerResult->getAnalyserResult()->getInternalErrors() as $internalError) {
 					$internalErrors[] = new InternalError(

tests/PHPStan/Analyser/ResultCache/ResultCacheManagerCollectedDataTest.php

@@ -234,11 +234,31 @@ public function testFileChangedAndChangedBackDuringTheAnalysisIsAnalysedAgain():
 		file_put_contents($a, $hashed);
 		$processed = $manager->process($this->analyserResult([], [], [$a]), $resultCache, $this->nullOutput(), false, true);
 		$this->assertTrue($processed->save(new FinalizerResult($processed->getAnalyserResult(), [], [])));
+		$this->assertSame([$a => true], $manager->getFilesChangedDuringAnalysis($resultCache));
 
 		$resultCache = $this->createManager()->restore($this->files, false, false, null, $this->nullOutput());
 		$this->assertSame([$a], $resultCache->getFilesToAnalyse());
 	}
 
+	public function testNoFilesChangedDuringTheAnalysis(): void
+	{
+		$a = $this->files[0];
+		$this->saveFullAnalysis([]);
+		$this->waitUntilTheFilesAreInThePast();
+
+		$manager = $this->createManager();
+		$resultCache = $manager->restore($this->files, false, false, null, $this->nullOutput());
+		$this->assertSame([], $resultCache->getFilesToAnalyse());
+		// a run that analysed nothing read nothing
+		file_put_contents($a, "<?php class Cachea { public function m(): string {} }\n");
+		$this->assertSame([], $manager->getFilesChangedDuringAnalysis($resultCache));
+
+		$manager = $this->createManager();
+		$resultCache = $manager->restore($this->files, false, false, null, $this->nullOutput());
+		$this->assertSame([$a], $resultCache->getFilesToAnalyse());
+		$this->assertSame([], $manager->getFilesChangedDuringAnalysis($resultCache));
+	}
+
 	/**
 	 * A save keeps the stat signature only of a file not modified in the second the save began,
 	 * so without waiting, saves on both sides of a second boundary differ in their signatures.