From 248664082410b9f48cabd02eec054299f73d88e7 Mon Sep 17 00:00:00 2001
From: Stephen Jennings <stephen.g.jennings@gmail.com>
Date: Wed, 15 Apr 2026 15:15:42 -0700
Subject: [PATCH] fix: Tolerate missing directories when formatting from stdin

When formatting code passed via stdin, and using `--stdin-path`, the
path passed may not exist. This is the case when using CSharpier as a
[jj] fix tool: Commits are not checked out, so the directory containing
the file being formatted may not actually exist on disk.

When this happened, CSharpier was throwing a DirectoryNotFoundException
from FindForDirectoryName in CSharpierConfigParser.

Instead, we can predict this exception and check for configuration in
the parent directory, until we find one that does exist.

jj: https://jj-vcs.dev
---
 Src/CSharpier.Cli/CommandLineFormatter.cs        |  9 +++++++++
 Src/CSharpier.Cli/Options/OptionsProvider.cs     |  5 ++++-
 Src/CSharpier.Tests/CommandLineFormatterTests.cs | 14 ++++++++++++++
 3 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/Src/CSharpier.Cli/CommandLineFormatter.cs b/Src/CSharpier.Cli/CommandLineFormatter.cs
index d8728908c..83c8fbdf5 100644
--- a/Src/CSharpier.Cli/CommandLineFormatter.cs
+++ b/Src/CSharpier.Cli/CommandLineFormatter.cs
@@ -40,6 +40,15 @@ CancellationToken cancellationToken
                     filePath = directoryPath;
                     directoryPath = fileSystem.Path.GetDirectoryName(directoryPath);
                     ArgumentNullException.ThrowIfNull(directoryPath);
+
+                    // The directory from --stdin-path may not exist on disk.
+                    // Walk up to the nearest existing ancestor for config resolution.
+                    while (!fileSystem.Directory.Exists(directoryPath))
+                    {
+                        directoryPath = fileSystem.Path.GetDirectoryName(directoryPath);
+                        ArgumentNullException.ThrowIfNull(directoryPath);
+                    }
+
                     pathSupplied = true;
                 }
                 // otherwise someone is running this as a single command and not sending a path
diff --git a/Src/CSharpier.Cli/Options/OptionsProvider.cs b/Src/CSharpier.Cli/Options/OptionsProvider.cs
index da223bbf8..132326b79 100644
--- a/Src/CSharpier.Cli/Options/OptionsProvider.cs
+++ b/Src/CSharpier.Cli/Options/OptionsProvider.cs
@@ -253,7 +253,10 @@ searchingDirectory is not null
             && !dictionary.TryGetValue(searchingDirectory.FullName, out result)
         )
         {
-            if (shouldConsiderDirectory(searchingDirectory.FullName))
+            if (
+                this.fileSystem.Directory.Exists(searchingDirectory.FullName)
+                && shouldConsiderDirectory(searchingDirectory.FullName)
+            )
             {
                 dictionary[searchingDirectory.FullName] = result = await createFileAsync(
                     searchingDirectory.FullName
diff --git a/Src/CSharpier.Tests/CommandLineFormatterTests.cs b/Src/CSharpier.Tests/CommandLineFormatterTests.cs
index 3cc6dae43..59f439415 100644
--- a/Src/CSharpier.Tests/CommandLineFormatterTests.cs
+++ b/Src/CSharpier.Tests/CommandLineFormatterTests.cs
@@ -781,6 +781,20 @@ public void Should_Format_StandardInput_And_Not_Consider_Gitignore_When_No_Path_
         result.OutputLines.First().Should().Be(FormattedClassContent);
     }
 
+    [Test]
+    public void Should_Format_StandardInput_When_StdinFilePath_Directory_Does_Not_Exist()
+    {
+        var context = new TestContext();
+        var result = Format(
+            context,
+            standardInFileContents: UnformattedClassContent,
+            directoryOrFilePaths: "NonExistent/SubDir/File.cs"
+        );
+
+        result.OutputLines.Should().ContainSingle();
+        result.OutputLines.First().Should().Be(FormattedClassContent);
+    }
+
     [Test]
     public void File_With_Mismatched_Line_Endings_In_Verbatim_String_Should_Pass_Validation()
     {