How to output a file from a roslyn code analyzer?

Question

I'm using the roslyn API to write a DiagnosticAnalyzer and CodeFix.

After I have collected all strings and string-interpolations, I want to write all of them to a file but I am not sure how to do this the best way.

Of course I can always simply do a File.WriteAllText(...) but I'd like to expose more control to the user.

I'm also not sure about how to best trigger the generation of this file, so my questions are:

1. I do not want to hard-code the filename, what would be the best way to expose this setting to the user of the code-analyzer? A config file? If so, how would I access that? ie: How do I know the directory?

2. If one string is missing from the file, I'd like to to suggest a code fix like "Project contains changed or new strings, regenerate string file". Is this the best way to do this? Or is it possible to add a button or something to visual studio?

3. I'm calling the devenv.com executable from the commandline to trigger builds, is there a way to force my code-fix to run either while building, or before/after? Or would I have to "manually" load the solution with roslyn and execute my codefix?

Answer 1

For config files you can use the AdditionalFiles msbuild property, which is passed to the analyzers through the context. See here.

Answer 2

I've just completed a project on this. There are a few things that you will need to do / know.

1. You will probably need to switch you're portable class library to a class library. otherwise you will have trouble calling the File.WriteAllText()

You can see how to Convert a portable class library to a regular here

2. This will potentially not appropriately work for when trying to apply all changes to document/project/solution. When Calling from a document/project/solution, the changes are precalcuated and applied in a preview window. If you cancel, an undo action is triggered to undo all changes, if you write to a file during this time, and do not register an undo action you will not undo the changes to the file.

I've opened a bug with roslyn but you can handle instances by override the preview you can see how to do so here

3. And one more final thing you may need to know is how to access the Solution from the analyzer which, Currently there is a hack I've written to do so here

4. As Tamas said you can use additional files you can see how to do so here

You can use additional files, but I know on the version I'm using resource files, are not marked as additional files by default they are embeddedResources.
So, for my users to not have to manually mark the resource as additonalFiles I wrote a function to get out the Designer.cs files associated with resource files from the csproj file using xDoc you can use it as an example if you choose to parse the csproj file:

protected List<string> GetEmbeddedResourceResxDocumentPaths(Project project)
{
    XDocument xmldoc = XDocument.Load(project.FilePath);
    XNamespace msbuild = "http://schemas.microsoft.com/developer/msbuild/2003";

    var resxFiles = new List<string>();
    foreach (var resource in xmldoc.Descendants(msbuild + "EmbeddedResource"))
    {
        string includePath = resource.Attribute("Include").Value;

        var includeExtension = Path.GetExtension(includePath);
        if (0 == string.Compare(includeExtension, RESX_FILE_EXTENSION, StringComparison.OrdinalIgnoreCase))
        {
            var outputTag = resource.Elements(msbuild + LAST_GENERATED_TAG).FirstOrDefault();

            if (null != outputTag)
            {
                resxFiles.Add(outputTag.Value);
            }
        }
    }
    return resxFiles;
}