Override fsharp source location via FSHARP_REPO env var.

Author: nojaf

FSharp.Compiler.Service/FSharp.Compiler.Service.fsproj

@@ -22,6 +22,9 @@
 
     <!-- for a local checkout and build of fsharp in CI -->
     <TargetPath Condition="Exists('..\fsharp\Build.cmd')">$(MSBuildThisFileDirectory)..\fsharp\artifacts\bin\FSharp.Compiler.Service\Debug\netstandard2.0\FSharp.Compiler.Service.dll</TargetPath>
+
+    <!-- for an existing checkout of fsharp, see FSHARP_REPO in build.fsx -->
+    <TargetPath Condition="'$(FSHARP_REPO)' != '' And Exists('$(FSHARP_REPO)/Build.cmd')">$(FSHARP_REPO)/artifacts/bin/FSharp.Compiler.Service/Debug/netstandard2.0/FSharp.Compiler.Service.dll</TargetPath>
 
   </PropertyGroup>
   <PropertyGroup>

README.md

@@ -29,6 +29,12 @@ You need a .NET 10 SDK to run it. The default pipeline does the following:
 
 To pick up new upstream changes, delete the `fsharp` folder and run the pipeline again.
 
+To generate the docs from a dotnet/fsharp checkout you already have, for example a fork with
+docs changes in progress, point `FSHARP_REPO` at it. The clone step is skipped and that checkout
+is built and read in place:
+
+    FSHARP_REPO=~/Projects/fsharp dotnet fsi build.fsx
+
 Once a build has run, iterate on the docs with live reload:
 
     dotnet fsi build.fsx -- -p Watch

build.fsx

@@ -7,9 +7,20 @@ open Fun.Build
 
 let root = __SOURCE_DIRECTORY__
 
-/// A shallow clone of dotnet/fsharp main. It is git-ignored; the docs are generated from its
-/// `docs` folder and from the FSharp.Compiler.Service it builds.
-let fsharpDir = Path.Combine(root, "fsharp")
+/// Set this to the path of an existing dotnet/fsharp checkout to generate the docs from it
+/// instead of the shallow clone the pipeline makes. Handy when iterating on docs changes in
+/// a local fork: the clone stage is skipped and the checkout is built and read in place.
+let fsharpRepoEnvVar = "FSHARP_REPO"
+
+/// The dotnet/fsharp checkout the docs are generated from: its `docs` folder and the
+/// FSharp.Compiler.Service it builds. By default a git-ignored shallow clone of main.
+let fsharpRepo = Environment.GetEnvironmentVariable fsharpRepoEnvVar
+
+let fsharpDir =
+    if String.IsNullOrEmpty fsharpRepo then
+        Path.Combine(root, "fsharp")
+    else
+        Path.GetFullPath fsharpRepo
 
 /// The SDK bootstrap script dotnet/fsharp ships. It runs its arguments with the exact SDK that
 /// `fsharp/global.json` asks for, installing it under `fsharp/.dotnet` first when this machine
@@ -25,7 +36,13 @@ let cloneStage =
     stage "clone fsharp" {
         run (fun ctx ->
             async {
-                if Directory.Exists fsharpDir then
+                if not (String.IsNullOrEmpty fsharpRepo) then
+                    if Directory.Exists fsharpDir then
+                        printfn $"Using the dotnet/fsharp checkout at {fsharpDir} ({fsharpRepoEnvVar})."
+                        return Ok()
+                    else
+                        return Error $"{fsharpRepoEnvVar} points to {fsharpDir}, which does not exist."
+                elif Directory.Exists fsharpDir then
                     printfn "fsharp/ already exists, not cloning. Delete it to start from a fresh checkout."
                     return Ok()
                 else
@@ -47,10 +64,16 @@ let restoreStage =
 
 /// fsdocs targets a fixed .NET runtime. Let it run on whatever newer runtime the machine has,
 /// prereleases included, so the SDK dotnet/fsharp needs is also enough to run the tool.
+/// FSHARP_REPO is passed on so FSharp.Compiler.Service.fsproj resolves the assembly from the
+/// same checkout.
 let fsdocsEnv =
-    [ "DOTNET_ROLL_FORWARD", "LatestMajor"; "DOTNET_ROLL_FORWARD_TO_PRERELEASE", "1" ]
+    [ "DOTNET_ROLL_FORWARD", "LatestMajor"
+      "DOTNET_ROLL_FORWARD_TO_PRERELEASE", "1"
+      fsharpRepoEnvVar, fsharpDir ]
 
-let fsdocsArgs = "--eval --sourcefolder fsharp --input fsharp/docs"
+let fsdocsArgs =
+    let docsDir = Path.Combine(fsharpDir, "docs")
+    $"--eval --sourcefolder \"{fsharpDir}\" --input \"{docsDir}\""
 
 pipeline "Build" {
     description "Clone dotnet/fsharp, build FSharp.Compiler.Service and generate the docs into output/."
@@ -60,7 +83,8 @@ pipeline "Build" {
     restoreStage
     stage "docs" {
         envVars fsdocsEnv
-        run $"dotnet fsdocs build {fsdocsArgs}"
+        // --clean so pages from a previous build against another checkout never linger in output/.
+        run $"dotnet fsdocs build --clean {fsdocsArgs}"
     }
     runIfOnlySpecified false
 }