omnisharp-roslyn: build from source

- use links for internal msbuild
- add dotnet-sdk to PATH
  https://github.com/NixOS/nixpkgs/pull/98435#issuecomment-715508615
- build from source
- add myself as maintainer

pkgs/development/tools/omnisharp-roslyn/create-deps.sh

@@ -0,0 +1,66 @@
+#!/usr/bin/env nix-shell
+#!nix-shell -i bash -p msbuild -p jq -p xmlstarlet -p curl
+set -euo pipefail
+
+cat << EOL
+{ fetchurl }: [
+EOL
+
+tmpdir="$(mktemp -d -p "$(pwd)")" # must be under source root
+trap 'rm -rf "$tmpdir"' EXIT
+
+mapfile -t repos < <(
+    xmlstarlet sel -t -v 'configuration/packageSources/add/@value' -n NuGet.Config |
+        while IFS= read index
+        do
+            curl --compressed -fsL "$index" | \
+                jq -r '.resources[] | select(."@type" == "PackageBaseAddress/3.0.0")."@id"'
+        done
+    )
+
+msbuild -t:restore -p:Configuration=Release -p:RestorePackagesPath="$tmpdir" \
+        -p:RestoreNoCache=true -p:RestoreForce=true \
+        src/OmniSharp.Stdio.Driver/OmniSharp.Stdio.Driver.csproj >&2
+
+cd "$tmpdir"
+for package in *
+do
+    cd "$package"
+    for version in *
+    do
+        found=false
+        for repo in "${repos[@]}"
+        do
+            url="$repo$package/$version/$package.$version.nupkg"
+            if curl -fsL "$url" -o /dev/null
+            then
+                found=true
+                break
+            fi
+        done
+
+        if ! $found
+        then
+            echo "couldn't find $package $version" >&2
+            exit 1
+        fi
+
+        sha256=$(nix-prefetch-url "$url" 2>/dev/null)
+        cat << EOL
+  {
+    name = "$package";
+    version = "$version";
+    src = fetchurl {
+      url = "$url";
+      sha256 = "$sha256";
+    };
+  }
+EOL
+    done
+    cd ..
+done
+cd ..
+
+cat << EOL
+]
+EOL

pkgs/development/tools/omnisharp-roslyn/default.nix

@@ -1,42 +1,104 @@
 { lib, stdenv
+, fetchFromGitHub
 , fetchurl
-, mono
+, mono6
 , msbuild
 , dotnet-sdk
 , makeWrapper
-, dotnetPackages
+, unzip
+, writeText
 }:
 
-stdenv.mkDerivation rec {
+let
+
+  deps = map (package: stdenv.mkDerivation (with package; {
+    pname = name;
+    inherit version src;
+
+    buildInputs = [ unzip ];
+    unpackPhase = ''
+      unzip $src
+      chmod -R u+r .
+      function traverseRename () {
+        for e in *
+        do
+          t="$(echo "$e" | sed -e "s/%20/\ /g" -e "s/%2B/+/g")"
+          [ "$t" != "$e" ] && mv -vn "$e" "$t"
+          if [ -d "$t" ]
+          then
+            cd "$t"
+            traverseRename
+            cd ..
+          fi
+        done
+      }
+
+      traverseRename
+    '';
+
+    installPhase = ''
+      runHook preInstall
+
+      package=$out/lib/dotnet/${name}/${version}
+      mkdir -p $package
+      cp -r . $package
+      echo "{}" > $package/.nupkg.metadata
+
+      runHook postInstall
+    '';
+
+    dontFixup = true;
+  }))
+    (import ./deps.nix { inherit fetchurl; });
+
+  nuget-config = writeText "NuGet.Config" ''
+    <?xml version="1.0" encoding="utf-8"?>
+    <configuration>
+      <packageSources>
+        <clear />
+      </packageSources>
+      <fallbackPackageFolders>
+        ${lib.concatStringsSep "\n" (map (package: "<add key=\"${package}\" value=\"${package}/lib/dotnet\"/>") deps)}
+      </fallbackPackageFolders>
+    </configuration>
+  '';
+
+in stdenv.mkDerivation rec {
 
   pname = "omnisharp-roslyn";
   version = "1.37.8";
 
-  src = fetchurl {
-    url = "https://github.com/OmniSharp/omnisharp-roslyn/releases/download/v${version}/omnisharp-mono.tar.gz";
-    sha256 = "0kgv4l15rli9a7grmcsbv72csmxi7vqa7lrrr8bd4cq9ighh54q3";
+  src = fetchFromGitHub {
+    owner = "OmniSharp";
+    repo = pname;
+    rev = "v${version}";
+    sha256 = "1zi31m6ngk4rm7444n6q7mim096w5h4j2biwmvwmcf5yvig845za";
   };
 
-  nativeBuildInputs = [ makeWrapper dotnet-sdk dotnetPackages.Nuget ];
+  nativeBuildInputs = [ makeWrapper msbuild ];
 
-  preUnpack = ''
-    mkdir src
-    cd src
-    sourceRoot=.
+  buildPhase = ''
+    runHook preBuild
+
+    HOME=$(pwd)/fake-home msbuild -r -p:Configuration=Release -p:RestoreConfigFile=${nuget-config} src/OmniSharp.Stdio.Driver/OmniSharp.Stdio.Driver.csproj
+
+    runHook postBuild
   '';
 
   installPhase = ''
     mkdir -p $out/bin
-    cd ..
-    cp -r src $out/
-    rm -r $out/src/.msbuild
-    cp -r ${msbuild}/lib/mono/msbuild $out/src/.msbuild
+    cp -r bin/Release/OmniSharp.Stdio.Driver/net472 $out/src
+    cp bin/Release/OmniSharp.Host/net472/SQLitePCLRaw* $out/src
+    mkdir $out/src/.msbuild
+    ln -s ${msbuild}/lib/mono/xbuild/* $out/src/.msbuild/
+    rm $out/src/.msbuild/Current
+    mkdir $out/src/.msbuild/Current
+    ln -s ${msbuild}/lib/mono/xbuild/Current/* $out/src/.msbuild/Current/
+    ln -s ${msbuild}/lib/mono/msbuild/Current/bin $out/src/.msbuild/Current/Bin
 
-    chmod -R u+w $out/src
-    mv $out/src/.msbuild/Current/{bin,Bin}
-
-    makeWrapper ${mono}/bin/mono $out/bin/omnisharp \
-    --add-flags "$out/src/OmniSharp.exe"
+    makeWrapper ${mono6}/bin/mono $out/bin/omnisharp \
+      --prefix PATH : ${dotnet-sdk}/bin \
+      --add-flags "$out/src/OmniSharp.exe"
   '';
 
   meta = with lib; {
@@ -44,7 +106,7 @@ stdenv.mkDerivation rec {
     homepage = "https://github.com/OmniSharp/omnisharp-roslyn";
     platforms = platforms.linux;
     license = licenses.mit;
-    maintainers = with maintainers; [ tesq0 ericdallo ];
+    maintainers = with maintainers; [ tesq0 ericdallo corngood ];
   };
 
 }