Nullean.Entities.FileSystem 0.1.0-preview.1

Nullean.Entities.FileSystem

Constraint shapes for files and directories, over the System.IO.Abstractions types a domain model already holds (IFileInfo, IDirectoryInfo).

[Constraints]
public static partial class DocsetConstraints
{
    public static readonly Constraint<Docset> ImagesExist       = Files<Docset>.Exist(d => d.Images);
    public static readonly Constraint<Docset> ImagesStayInRoot  = Files<Docset>.StayInside(d => d.Root, d => d.Images);
    public static readonly Constraint<Docset> NoSymlinks        = Files<Docset>.NotSymlink(d => d.Images, d => d.Root);
    public static readonly Constraint<Docset> NoHiddenFolders   = Files<Docset>.NoHiddenSegments(d => d.Root, d => d.Images);
    public static readonly Constraint<Docset> PictureExtensions = Files<Docset>.HaveExtension(d => d.Images, [".png", ".svg"]);
}

Each takes message: (one text for every finding), describe: (a text per path) and at: (a SourceLocation for the item, so a finding can point at the YAML line), and reports the selected member as Violation.Member. Use .WithSeverity(Severity.Warning) for a rule that is not an error yet.

When the model's items are not files (a table-of-contents entry, a redirect target), Exist and DirectoriesExist take the items and a function that resolves each to the file it names; describe and at then speak about the item:

Files<Docset>.DirectoriesExist(
    d => d.Folders,                                   // the entries
    (d, f) => d.FileSystem.DirectoryInfo.New(Path.Join(d.Root.FullName, f.Path)),
    describe: f => $"Folder '{f.Path}' does not exist.",
    at: f => new SourceLocation(f.File, f.Line, f.Column, f.Path.Length));

FilePaths is the path arithmetic the shapes use, public for a rule that needs the answer inside a larger check: IsInside(root, path, comparison), SymlinkAt, HiddenSegment, and UnsafeToRead(path, root), the reason a path may not be read as content (a link, or a hidden directory, on the way) or null. A chain that stops at the first problem (right extension, inside the root, safe to read, exists) keeps its own wording and asks FilePaths instead of re-deriving the rules. The rules read the file system the path came from (IFileSystemInfo.FileSystem), so a test that builds the model on a MockFileSystem checks the very code that runs against the disk. A path the file system refuses is reported as a violation of that rule, not thrown.

The package is trim and AOT clean: ./build.sh aot publishes an app using these rules NativeAOT. To get counter-examples for them with no hand-written file system, see Nullean.Entities.CsCheck.FileSystem.