Fix spurious 'fsi is not defined' error during literate script type-checking (#1140)

* Fix spurious 'fsi is not defined' error during literate script type-checking

When literate scripts use fsi.AddPrinter or related APIs, the type-checker
reported a spurious error because FSharp.Compiler.Interactive.Settings.dll
was not referenced. GetProjectOptionsFromScript does not include this
reference automatically in any configuration.

Add a lazy resolver (fsiSettingsDll) that locates the DLL from either
AppContext.BaseDirectory or the SDK's FSharp directory, and include it
as an explicit -r: reference when building project options for
type-checking in CodeFormatAgent.

Fixes #1139

* Update RELEASE_NOTES.md for version 22.0.0-alpha.3

Add release notes for version 22.0.0-alpha.3 with fixes.

Author: dsyme

RELEASE_NOTES.md

@@ -2,7 +2,10 @@
 
 ## [Unreleased]
 
+## [22.0.0-alpha.3] - 2026-04-02
+
 ### Fixed
+* Fix spurious `'fsi' is not defined` error during literate script type-checking when scripts use `fsi.AddPrinter` or related APIs. The `FSharp.Compiler.Interactive.Settings.dll` reference is now explicitly added to the type-checker options. [#1139](https://github.com/fsprojects/FSharp.Formatting/issues/1139)
 * Fix literate script comment parser prematurely closing `(**` blocks when the markdown text contained nested `(*** ... ***)` references (e.g. in backtick-quoted command examples), causing subsequent content to be silently dropped from HTML output.
 * Add missing `[<Test>]` attribute on `Can include-output-and-it` test so it is executed by the test runner.
 * Add regression test confirming that types whose name matches their enclosing namespace are correctly included in generated API docs. [#944](https://github.com/fsprojects/FSharp.Formatting/issues/944)

src/FSharp.Formatting.CodeFormat/CodeFormatAgent.fs

@@ -421,6 +421,12 @@ module CodeFormatter =
                            if Env.isNetCoreApp then
                                yield "--targetprofile:netcore"
 
+                           // Add FSharp.Compiler.Interactive.Settings.dll so that the
+                           // type-checker can resolve the 'fsi' object in .fsx scripts.
+                           match FSharpAssemblyHelper.fsiSettingsDll.Value with
+                           | Some path -> yield sprintf "-r:%s" path
+                           | None -> ()
+
                            yield! opts.OtherOptions |]
                         |> Array.filter (fun item ->
                             if item.StartsWith("-r:", StringComparison.Ordinal) then

src/FSharp.Formatting.Common/YaafFSharpScripting.fs

@@ -119,6 +119,42 @@ module internal CompilerServiceExtensions =
               yield! libDirs
               yield System.IO.Directory.GetCurrentDirectory() ]
 
+        /// Lazily locates an <c>FSharp.Compiler.Interactive.Settings.dll</c> so the type-checker
+        /// can resolve the <c>fsi</c> object in <c>.fsx</c> scripts.
+        let fsiSettingsDll =
+            lazy
+                (let settingsName = "FSharp.Compiler.Interactive.Settings.dll"
+
+                 // Strategy 1: next to the running process
+                 let candidate1 = AppContext.BaseDirectory ++ settingsName
+
+                 if File.Exists candidate1 then
+                     Some candidate1
+                 else
+                     // Strategy 2: search the SDK FSharp directory,
+                     // derived from the shared-framework location of System.Private.CoreLib.
+                     try
+                         let coreLib = typeof<obj>.Assembly.Location
+
+                         if not (System.String.IsNullOrEmpty coreLib) then
+                             // coreLib is e.g. /usr/lib/dotnet/shared/Microsoft.NETCore.App/<ver>/System.Private.CoreLib.dll
+                             let sharedVerDir = Path.GetDirectoryName coreLib
+                             let dotnetBase = Path.GetFullPath(sharedVerDir ++ ".." ++ ".." ++ "..")
+                             let sdkDir = dotnetBase ++ "sdk"
+
+                             if Directory.Exists sdkDir then
+                                 Directory.GetDirectories sdkDir
+                                 |> Array.sortDescending
+                                 |> Array.tryPick (fun dir ->
+                                     let c = dir ++ "FSharp" ++ settingsName
+                                     if File.Exists c then Some c else None)
+                             else
+                                 None
+                         else
+                             None
+                     with _ ->
+                         None)
+
         /// Returns <c>Some path</c> if a file exists at <paramref name="fscorePath"/>, otherwise <c>None</c>.
         let tryCheckFsCore fscorePath =
             if File.Exists fscorePath then Some fscorePath else None

tests/FSharp.Literate.Tests/EvalTests.fs

@@ -712,3 +712,22 @@ Wrapped "TRANSFORMED"
 
     let html1 = Literate.ToHtml(doc1)
     html1 |> shouldContainText "<em>TRANSFORMED</em>"
+
+[<Test>]
+let ``fsi.AddPrinter does not produce spurious 'fsi is not defined' diagnostic`` () =
+    let content =
+        """
+type Foo = { X: int }
+fsi.AddPrinter(fun (f: Foo) -> sprintf "FOO(%d)" f.X)
+let v = { X = 42 }
+v
+(*** include-it ***)
+"""
+
+    let fsie = getFsiEvaluator ()
+
+    let doc1 = Literate.ParseScriptString(content, "." </> "A.fsx", fsiEvaluator = fsie)
+
+    doc1.Diagnostics.Length |> shouldEqual 0
+    let html1 = Literate.ToHtml(doc1)
+    html1 |> shouldContainText "FOO(42)"