Fix project restore detection for nonstandard artifact locations

When a project doesn't place project.assets.json under <projDir>/obj/
(e.g. UseArtifactsOutput or projects like dotnet/fsharp with custom
output layout), the fallback MSBuild --getProperty call may itself fail.
Previously that failure was hard-coded to throw, making it impossible
to use fsdocs on such repos.

Following the maintainer suggestion from issue #592, change the
fallback so that:
- If MSBuild succeeds and reports an assets path that exists -> OK
- If MSBuild succeeds but the assets file doesn't exist -> fail fast
  (project definitely not restored)
- If MSBuild fails (e.g. old SDK, nonstandard project) -> warn and
  proceed, letting the cracking step produce the definitive error

Closes #592

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: 2 people

RELEASE_NOTES.md

@@ -12,6 +12,7 @@
 * `IFsiEvaluator` now inherits `IDisposable`; `FsiEvaluator` disposes its underlying FSI session when disposed, preventing session leaks in long-running processes. [#341](https://github.com/fsprojects/FSharp.Formatting/issues/341)
 
 ### Fixed
+* Fix project restore detection for projects with nonstandard artifact locations (e.g. `<UseArtifactsOutput>` or the dotnet/fsharp repo layout): when the MSBuild call to locate `project.assets.json` fails, emit a warning and proceed instead of hard-failing. [#592](https://github.com/fsprojects/FSharp.Formatting/issues/592)
 * Fix doc generation failure for members with 5D/6D+ array parameters by correctly formatting array type signatures in XML doc format (e.g. `System.Double[0:,0:,0:,0:,0:]` for a 5D array). [#702](https://github.com/fsprojects/FSharp.Formatting/issues/702)
 * Fix `_menu_template.html` and `_menu-item_template.html` being copied to the output directory. [#803](https://github.com/fsprojects/FSharp.Formatting/issues/803)
 * Fix `ApiDocMember.Details.ReturnInfo.ReturnType` returning `None` for properties that have both a getter and a setter. [#734](https://github.com/fsprojects/FSharp.Formatting/issues/734)

src/fsdocs-tool/ProjectCracker.fs

@@ -372,15 +372,28 @@ module Crack =
             ()
         else
             // In dotnet 8 <UseArtifactsOutput> was introduced, see https://learn.microsoft.com/en-us/dotnet/core/sdk/artifacts-output
-            // We will try and use CLI-based project evaluation to determine the location of project.assets.json file
+            // We will try and use CLI-based project evaluation to determine the location of project.assets.json file.
             // See https://learn.microsoft.com/en-us/dotnet/core/whats-new/dotnet-8#cli-based-project-evaluation
-            try
-                let path = DotNetCli.msbuild projDir "--getProperty:ProjectAssetsFile"
+            // Some projects (e.g. those with nonstandard artifact output locations) may not put project.assets.json
+            // under <projDir>/obj/. If we can detect the actual path via MSBuild, we use that; otherwise we warn
+            // and proceed so that the cracking step itself can produce the definitive error.
+            let detectedPath =
+                try
+                    let path = DotNetCli.msbuild projDir "--getProperty:ProjectAssetsFile"
+                    Some path
+                with _ ->
+                    None
 
-                if not (File.Exists path) then
-                    failwithf $"project '%s{file}' not restored"
-            with ex ->
-                failwithf $"Failed to detect if the project '%s{file}' was restored"
+            match detectedPath with
+            | Some path when File.Exists path -> ()
+            | Some _ ->
+                // MSBuild reported a path but the file doesn't exist there — project is definitely not restored.
+                failwithf $"project '%s{file}' not restored"
+            | None ->
+                // Could not determine the assets file location (e.g. old SDK without --getProperty support,
+                // or nonstandard project layout). Warn and continue; if the project truly isn't restored the
+                // subsequent cracking step will fail with a more specific error.
+                printfn $"Warning: could not verify that project '%s{file}' was restored. Proceeding anyway."
 
     let crackProjectFile slnDir extraMsbuildProperties (file: string) : CrackedProjectInfo =
         ensureProjectWasRestored file