Deduplicate module names

src/fsharp/fsc.fs

@@ -1761,6 +1761,38 @@ let main0(ctok, argv, referenceResolver, bannerAlreadyPrinted, exiter:Exiter, er
         with e -> 
             errorRecoveryNoRange e
             exiter.Exit 1
+
+    let inputs =
+        // Deduplicate module names
+        let seen = Dictionary<string,Set<string>>()
+        let deduplicate (paths: Set<string>) path (qualifiedNameOfFile: QualifiedNameOfFile) =
+            let count = if paths.Contains path then paths.Count else paths.Count + 1
+            seen.[qualifiedNameOfFile.Text] <- Set.add path paths
+            let id = qualifiedNameOfFile.Id
+            if count = 1 then qualifiedNameOfFile else QualifiedNameOfFile(Ident(id.idText + "___" + count.ToString(),id.idRange))
+        inputs
+        |> List.map (fun (input,x) -> 
+            match input with
+            | ParsedInput.ImplFile (ParsedImplFileInput.ParsedImplFileInput(fileName,isScript,qualifiedNameOfFile,scopedPragmas,hashDirectives,modules,(isLastCompiland,isExe))) ->
+                let path = Path.GetDirectoryName fileName
+                match seen.TryGetValue qualifiedNameOfFile.Text with
+                | true, paths ->
+                    let qualifiedNameOfFile = deduplicate paths path qualifiedNameOfFile
+                    let input = ParsedInput.ImplFile(ParsedImplFileInput.ParsedImplFileInput(fileName,isScript,qualifiedNameOfFile,scopedPragmas,hashDirectives,modules,(isLastCompiland,isExe)))
+                    input,x
+                | _ ->
+                    seen.Add(qualifiedNameOfFile.Text,Set.singleton path)
+                    input,x
+            | ParsedInput.SigFile (ParsedSigFileInput.ParsedSigFileInput(fileName,qualifiedNameOfFile,scopedPragmas,hashDirectives,modules)) ->
+                let path = Path.GetDirectoryName fileName
+                match seen.TryGetValue qualifiedNameOfFile.Text with
+                | true, paths ->
+                    let qualifiedNameOfFile = deduplicate paths path qualifiedNameOfFile
+                    let input = ParsedInput.SigFile (ParsedSigFileInput.ParsedSigFileInput(fileName,qualifiedNameOfFile,scopedPragmas,hashDirectives,modules))
+                    input,x
+                | _ ->
+                    seen.Add(qualifiedNameOfFile.Text,Set.singleton path)
+                    input,x)
 
     if tcConfig.parseOnly then exiter.Exit 0 
     if not tcConfig.continueAfterParseFailure then 

tests/fsharp/core/samename/folder1/a.fs

@@ -0,0 +1,5 @@
+namespace tempet
+
+module SayA =
+    let hello name =
+        printfn "Hello %s" name

tests/fsharp/core/samename/folder1/a.fsi

@@ -0,0 +1,4 @@
+namespace tempet
+
+module SayA =
+    val hello : string -> unit

tests/fsharp/core/samename/folder1/b.fs

@@ -0,0 +1,5 @@
+namespace tempet
+
+module SayB =
+    let hello name =
+        printfn "Hello %s" name

tests/fsharp/core/samename/folder1/b.fsi

@@ -0,0 +1,4 @@
+namespace tempet
+
+module SayB =
+    val hello : string -> unit

tests/fsharp/core/samename/folder2/a.fs

@@ -0,0 +1,5 @@
+namespace tempet
+
+module SayC =
+    let hello name =
+        printfn "Hello %s" name

tests/fsharp/core/samename/folder2/a.fsi

@@ -0,0 +1,4 @@
+namespace tempet
+
+module SayC =
+    val hello : string -> unit

tests/fsharp/core/samename/folder2/b.fs

@@ -0,0 +1,5 @@
+namespace tempet
+
+module SayD =
+    let hello name =
+        printfn "Hello %s" name

tests/fsharp/core/samename/folder2/b.fsi

@@ -0,0 +1,4 @@
+namespace tempet
+
+module SayD =
+    val hello : string -> unit

tests/fsharp/core/samename/tempet.fsproj

@@ -0,0 +1,23 @@
+<Project Sdk="FSharp.NET.Sdk;Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>netstandard1.6</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="folder1/a.fsi" />
+    <Compile Include="folder1/a.fs" />
+    <Compile Include="folder1/b.fsi" />
+    <Compile Include="folder1/b.fs" />
+    <Compile Include="folder2/a.fsi" />
+    <Compile Include="folder2/a.fs" />
+    <Compile Include="folder2/b.fsi" />
+    <Compile Include="folder2/b.fs" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="FSharp.Core" Version="4.1.*" />
+    <PackageReference Include="FSharp.NET.Sdk" Version="1.0.*" PrivateAssets="All" />
+  </ItemGroup>
+
+</Project>

tests/fsharp/tests.fs

@@ -774,7 +774,41 @@ module CoreTests =
         peverify cfg "test2.exe"
 
         exec cfg ("." ++ "test2.exe") ""
-
+
+    // Repro for https://github.com/Microsoft/visualfsharp/issues/2679
+    [<Test>]
+    let ``add files with same name from different folders`` () = 
+        let cfg = testConfig "core/samename"
+
+        log "== Compiling F# Code with files with same name in different folders"
+        fsc cfg "%s -o:test.exe" cfg.fsc_flags ["folder1/a.fs"; "folder1/b.fs"; "folder2/a.fs"; "folder2/b.fs"]
+
+        peverify cfg "test.exe"
+
+        exec cfg ("." ++ "test.exe") ""
+
+    [<Test>]
+    let ``add files with same name from different folders including signature files`` () =
+        let cfg = testConfig "core/samename"
+
+        log "== Compiling F# Code with files with same name in different folders including signature files"
+        fsc cfg "%s -o:test.exe" cfg.fsc_flags ["folder1/a.fsi"; "folder1/a.fs"; "folder1/b.fsi"; "folder1/b.fs"; "folder2/a.fsi"; "folder2/a.fs"; "folder2/b.fsi"; "folder2/b.fs"]
+
+        peverify cfg "test.exe"
+
+        exec cfg ("." ++ "test.exe") ""
+
+    [<Test>]
+    let ``add files with same name from different folders including signature files that are not synced`` () =
+        let cfg = testConfig "core/samename"
+
+        log "== Compiling F# Code with files with same name in different folders including signature files"
+        fsc cfg "%s -o:test.exe" cfg.fsc_flags ["folder1/a.fsi"; "folder1/a.fs"; "folder1/b.fs"; "folder2/a.fsi"; "folder2/a.fs"; "folder2/b.fsi"; "folder2/b.fs"]
+
+        peverify cfg "test.exe"
+
+        exec cfg ("." ++ "test.exe") ""
+
     [<Test>]
     let ``libtest-FSI_STDIN`` () = singleTestBuildAndRun "core/libtest" FSI_STDIN