port fsih to fsi as a hash directive

docs/release-notes/.FSharp.Compiler.Service/8.0.400.md

@@ -1,5 +1,6 @@
 ### Fixed
 
+* Added #h directive to fsi to show documentation in the REPL. ([PR #17140](https://github.com/dotnet/fsharp/pull/17140))
 * Optimize simple mappings with preludes in computed collections. ([PR #17067](https://github.com/dotnet/fsharp/pull/17067))
 * Improve error reporting for abstract members when used in classes. ([PR #17063](https://github.com/dotnet/fsharp/pull/17063))
 * Improve error reporting when property has same name as DU case. ([Issue #16646](https://github.com/dotnet/fsharp/issues/16646), [PR #17088](https://github.com/dotnet/fsharp/pull/17088))

src/Compiler/Interactive/FSIstrings.txt

@@ -32,6 +32,7 @@ fsiIntroPackageSourceUriInfo,"Include package source uri when searching for pack
 fsiIntroTextHashloadInfo,"Load the given file(s) as if compiled and referenced"
 fsiIntroTextHashtimeInfo,"Toggle timing on/off"
 fsiIntroTextHashhelpInfo,"Display help"
+fsiIntroTextfsihelpInfo,"Display documentation for an expression, e.g. fsi.h List.map;;"
 fsiIntroTextHashquitInfo,"Exit"
 fsiIntroTextHashclearInfo,"Clear screen"
 fsiIntroTextHeader2commandLine,"  F# Interactive command line options:"

src/Compiler/Interactive/fsi.fs

@@ -1251,6 +1251,7 @@ type internal FsiCommandLineOptions(fsi: FsiEvaluationSessionHostConfig, argv: s
 
         fsiConsoleOutput.uprintfn """    #clear;;                                      // %s""" (FSIstrings.SR.fsiIntroTextHashclearInfo ())
         fsiConsoleOutput.uprintfn """    #quit;;                                       // %s""" (FSIstrings.SR.fsiIntroTextHashquitInfo ())
+        fsiConsoleOutput.uprintfn """    fsi.h expr;;                                  // %s""" (FSIstrings.SR.fsiIntroTextfsihelpInfo ())
         fsiConsoleOutput.uprintfn ""
         fsiConsoleOutput.uprintfnn "%s" (FSIstrings.SR.fsiIntroTextHeader2commandLine ())
         fsiConsoleOutput.uprintfn "%s" (FSIstrings.SR.fsiIntroTextHeader3 (helpLine))

src/FSharp.Compiler.Interactive.Settings/FSharp.Compiler.Interactive.Settings.fsproj

@@ -32,6 +32,8 @@
 
   <ItemGroup>
     <EmbeddedText Include="FSInteractiveSettings.txt" />
+    <Compile Include="fsihelp.fsi" />
+    <Compile Include="fsihelp.fs" />
     <Compile Include="fsiattrs.fs" />
     <Compile Include="fsiaux.fsi" />
     <Compile Include="fsiaux.fs" />

src/FSharp.Compiler.Interactive.Settings/fsiaux.fs

@@ -162,6 +162,9 @@ type InteractiveSession() =
     member _.AddPrintTransformer(printer: 'T -> obj) =
         addedPrinters <- Choice2Of2(typeof<'T>, (fun (x: obj) -> printer (unbox x))) :: addedPrinters
 
+    member _.h([<ReflectedDefinition>] expr: Quotations.Expr<_>) =
+        FsiHelp.Logic.Quoted.tryGetDocumentation expr
+
     member internal self.SetEventLoop(run: (unit -> bool), invoke: ((unit -> obj) -> obj), restart: (unit -> unit)) =
         evLoop.ScheduleRestart()
 
@@ -178,6 +181,11 @@ type InteractiveSession() =
 module Settings =
     let fsi = new InteractiveSession()
 
+    fsi.AddPrinter<FsiHelp.Parser.Help option>(fun help ->
+        match help with
+        | None -> "No help available"
+        | Some help -> help.ToDisplayString())
+
     [<assembly: AutoOpen("FSharp.Compiler.Interactive.Settings")>]
     do ()
 

src/FSharp.Compiler.Interactive.Settings/fsiaux.fsi

@@ -68,6 +68,9 @@ type InteractiveSession =
     /// <summary>Gets or sets a the current event loop being used to process interactions.</summary>
     member EventLoop: IEventLoop with get, set
 
+    /// <summary>Get the documentation for an expression.</summary>
+    member h: [<ReflectedDefinition>] expr: Quotations.Expr<_> -> FsiHelp.Parser.Help option
+
     /// <summary>Sets the current event loop being used to process interactions.</summary>
     member internal SetEventLoop: (unit -> bool) * ((unit -> obj) -> obj) * (unit -> unit) -> unit