fix: support Tia when the Pest project is a subdirectory of the git repository

src/Plugins/Tia.php

@@ -9,7 +9,6 @@
 use Pest\Contracts\Plugins\HandlesArguments;
 use Pest\Contracts\Plugins\Terminable;
 use Pest\Exceptions\NoAffectedTestsFound;
-use Pest\Exceptions\TiaRequiresRepositoryRoot;
 use Pest\Panic;
 use Pest\Plugins\Concerns\HandleArguments;
 use Pest\Plugins\Tia\BaselineSync;
@@ -629,12 +628,6 @@ private function handleParent(array $arguments, string $projectRoot, bool $force
     {
         $this->watchPatterns->useDefaults($projectRoot);
 
-        $subdirectoryPrefix = $this->gitSubdirectoryPrefix($projectRoot);
-
-        if ($subdirectoryPrefix !== null) {
-            Panic::with(new TiaRequiresRepositoryRoot($subdirectoryPrefix));
-        }
-
         $this->branch = new ChangedFiles($projectRoot)->currentBranch() ?? 'main';
 
         $fingerprint = Fingerprint::compute($projectRoot);
@@ -1692,35 +1685,14 @@ private function formatStructuralDrift(array $drift): string
         return implode(', ', array_keys($seen));
     }
 
-    /**
-     * The path from the git repository root down to $projectRoot (e.g.
-     * `laravel-app`) when the project is nested inside a larger repo, or `null`
-     * when the project root is itself the repo root (or git is unavailable).
-     * TIA requires the two to coincide: git reports and addresses paths
-     * relative to the repo root, while the dependency graph is project-relative.
-     */
-    private function gitSubdirectoryPrefix(string $projectRoot): ?string
-    {
-        $process = new Process(['git', 'rev-parse', '--show-prefix'], $projectRoot);
-        $process->run();
-
-        if (! $process->isSuccessful()) {
-            return null;
-        }
-
-        $prefix = trim($process->getOutput());
-
-        return $prefix === '' ? null : rtrim(str_replace(DIRECTORY_SEPARATOR, '/', $prefix), '/');
-    }
-
     private function composerLockDelta(string $projectRoot, string $sha): string
     {
         $current = @file_get_contents($projectRoot.'/composer.lock');
         if ($current === false) {
             return '';
         }
 
-        $process = new Process(['git', 'show', $sha.':composer.lock'], $projectRoot);
+        $process = new Process(['git', 'show', $sha.':'.new ChangedFiles($projectRoot)->gitPrefix().'composer.lock'], $projectRoot);
         $process->setTimeout(5.0);
         $process->run();
 

src/Plugins/Tia/ChangedFiles.php

@@ -10,9 +10,58 @@
 /**
  * @internal
  */
-final readonly class ChangedFiles
+final class ChangedFiles
 {
-    public function __construct(private string $projectRoot) {}
+    private ?string $gitPrefix = null;
+
+    public function __construct(private readonly string $projectRoot) {}
+
+    /**
+     * The project root's path prefix inside the git repository, with a
+     * trailing slash (e.g. `backend/`), or an empty string when the project
+     * root is the repository root itself or git is unavailable. Git prints
+     * and addresses paths relative to the repository root, while the
+     * dependency graph is keyed on project-relative paths — the git
+     * boundaries below translate between the two using this prefix.
+     */
+    public function gitPrefix(): string
+    {
+        if ($this->gitPrefix !== null) {
+            return $this->gitPrefix;
+        }
+
+        $process = new Process(['git', 'rev-parse', '--show-prefix'], $this->projectRoot);
+        $process->run();
+
+        if (! $process->isSuccessful()) {
+            return $this->gitPrefix = '';
+        }
+
+        return $this->gitPrefix = str_replace(DIRECTORY_SEPARATOR, '/', trim($process->getOutput()));
+    }
+
+    /**
+     * @param  array<int, string>  $files  repository-relative paths as printed by git.
+     * @return array<int, string> project-relative paths; files outside the project are dropped.
+     */
+    private function toProjectRelative(array $files): array
+    {
+        $prefix = $this->gitPrefix();
+
+        if ($prefix === '') {
+            return $files;
+        }
+
+        $projectFiles = [];
+
+        foreach ($files as $file) {
+            if (str_starts_with($file, $prefix)) {
+                $projectFiles[] = substr($file, strlen($prefix));
+            }
+        }
+
+        return $projectFiles;
+    }
 
     /**
      * @param  array<int, string>  $files  project-relative paths.
@@ -155,7 +204,7 @@ private function filterBehaviourallyUnchanged(array $files, string $sha): array
 
     private function contentAtSha(string $sha, string $path): ?string
     {
-        $process = new Process(['git', 'show', $sha.':'.$path], $this->projectRoot);
+        $process = new Process(['git', 'show', $sha.':'.$this->gitPrefix().$path], $this->projectRoot);
         $process->setTimeout(5.0);
         $process->run();
 
@@ -245,7 +294,7 @@ private function diffSinceSha(string $sha): array
             throw new MissingDependency('Tia mode', 'git');
         }
 
-        return $this->splitLines($process->getOutput());
+        return $this->toProjectRelative($this->splitLines($process->getOutput()));
     }
 
     /**
@@ -297,7 +346,7 @@ private function workingTreeChanges(): array
             $files[] = $path;
         }
 
-        return $files;
+        return $this->toProjectRelative($files);
     }
 
     public function currentSha(): ?string

tests/Unit/Plugins/Tia/ChangedFiles.php

@@ -0,0 +1,155 @@
+<?php
+
+declare(strict_types=1);
+
+use Pest\Plugins\Tia\ChangedFiles;
+use Symfony\Component\Process\Process;
+
+function tia_changed_files_run(array $command, string $cwd): void
+{
+    $process = new Process($command, $cwd);
+    $process->mustRun();
+}
+
+/**
+ * Creates a git repository containing a `backend/` Pest project and a
+ * `frontend/` sibling package, with one initial commit.
+ *
+ * @return array{root: string, sha: string}
+ */
+function tia_changed_files_monorepo(): array
+{
+    $root = sys_get_temp_dir().DIRECTORY_SEPARATOR.'pest_tia_monorepo_'.uniqid();
+
+    mkdir($root.'/backend/app', 0o777, true);
+    mkdir($root.'/frontend', 0o777, true);
+
+    file_put_contents($root.'/backend/app/Service.php', "<?php\n\$a = 1;\n");
+    file_put_contents($root.'/backend/composer.lock', '{"packages": []}');
+    file_put_contents($root.'/frontend/widget.php', "<?php\n\$w = 1;\n");
+
+    tia_changed_files_run(['git', 'init', '-q', '-b', 'main'], $root);
+    tia_changed_files_run(['git', 'config', 'user.email', 'tia@pestphp.com'], $root);
+    tia_changed_files_run(['git', 'config', 'user.name', 'Tia'], $root);
+    tia_changed_files_run(['git', 'add', '-A'], $root);
+    tia_changed_files_run(['git', 'commit', '-q', '-m', 'initial'], $root);
+
+    $process = new Process(['git', 'rev-parse', 'HEAD'], $root);
+    $process->mustRun();
+
+    return ['root' => $root, 'sha' => trim($process->getOutput())];
+}
+
+function tia_changed_files_rm(string $directory): void
+{
+    $iterator = new RecursiveIteratorIterator(
+        new RecursiveDirectoryIterator($directory, FilesystemIterator::SKIP_DOTS),
+        RecursiveIteratorIterator::CHILD_FIRST,
+    );
+
+    foreach ($iterator as $file) {
+        $file->isDir() ? rmdir($file->getPathname()) : unlink($file->getPathname());
+    }
+
+    rmdir($directory);
+}
+
+describe('gitPrefix()', function (): void {
+    it('is empty at the repository root', function (): void {
+        $fixture = tia_changed_files_monorepo();
+
+        try {
+            expect(new ChangedFiles($fixture['root'])->gitPrefix())->toBeEmpty();
+        } finally {
+            tia_changed_files_rm($fixture['root']);
+        }
+    });
+
+    it('is the slash-terminated subdirectory path inside a larger repository', function (): void {
+        $fixture = tia_changed_files_monorepo();
+
+        try {
+            expect(new ChangedFiles($fixture['root'].'/backend')->gitPrefix())->toBe('backend/');
+        } finally {
+            tia_changed_files_rm($fixture['root']);
+        }
+    });
+
+    it('is empty outside any git repository', function (): void {
+        $directory = sys_get_temp_dir().DIRECTORY_SEPARATOR.'pest_tia_no_repo_'.uniqid();
+        mkdir($directory);
+
+        try {
+            expect(new ChangedFiles($directory)->gitPrefix())->toBeEmpty();
+        } finally {
+            tia_changed_files_rm($directory);
+        }
+    });
+});
+
+describe('a project in a repository subdirectory', function (): void {
+    it('reports working-tree changes as project-relative paths and drops sibling packages', function (): void {
+        $fixture = tia_changed_files_monorepo();
+
+        try {
+            file_put_contents($fixture['root'].'/backend/app/Service.php', "<?php\n\$a = 2;\n");
+            file_put_contents($fixture['root'].'/backend/app/Untracked.php', "<?php\n\$u = 1;\n");
+            file_put_contents($fixture['root'].'/frontend/widget.php', "<?php\n\$w = 2;\n");
+
+            $changed = new ChangedFiles($fixture['root'].'/backend')->since(null);
+
+            sort($changed);
+
+            expect($changed)->toBe(['app/Service.php', 'app/Untracked.php']);
+        } finally {
+            tia_changed_files_rm($fixture['root']);
+        }
+    });
+
+    it('reports committed changes since a sha as project-relative paths', function (): void {
+        $fixture = tia_changed_files_monorepo();
+
+        try {
+            file_put_contents($fixture['root'].'/backend/app/Service.php', "<?php\n\$a = 2;\n");
+            file_put_contents($fixture['root'].'/frontend/widget.php', "<?php\n\$w = 2;\n");
+            tia_changed_files_run(['git', 'commit', '-q', '-am', 'change both packages'], $fixture['root']);
+
+            expect(new ChangedFiles($fixture['root'].'/backend')->since($fixture['sha']))
+                ->toBe(['app/Service.php']);
+        } finally {
+            tia_changed_files_rm($fixture['root']);
+        }
+    });
+
+    it('filters files whose content is behaviourally unchanged against the baseline sha', function (): void {
+        $fixture = tia_changed_files_monorepo();
+
+        try {
+            file_put_contents($fixture['root'].'/backend/app/Service.php', "<?php\n\$a = 2;\n");
+            tia_changed_files_run(['git', 'commit', '-q', '-am', 'change service'], $fixture['root']);
+
+            // Reverting the content makes the file diff against the baseline
+            // sha while hashing identically to it — reachable only when
+            // `git show` receives the repository-relative path.
+            file_put_contents($fixture['root'].'/backend/app/Service.php', "<?php\n\$a = 1;\n");
+
+            expect(new ChangedFiles($fixture['root'].'/backend')->since($fixture['sha']))->toBe([]);
+        } finally {
+            tia_changed_files_rm($fixture['root']);
+        }
+    });
+});
+
+describe('a project at the repository root', function (): void {
+    it('still reports repository-relative paths untouched', function (): void {
+        $fixture = tia_changed_files_monorepo();
+
+        try {
+            file_put_contents($fixture['root'].'/backend/app/Service.php', "<?php\n\$a = 2;\n");
+
+            expect(new ChangedFiles($fixture['root'])->since(null))->toBe(['backend/app/Service.php']);
+        } finally {
+            tia_changed_files_rm($fixture['root']);
+        }
+    });
+});