nixd: provide package information on hover request (#430)

nixd/lib/Controller/Hover.cpp

@@ -3,21 +3,90 @@
 /// [Hover Request]:
 /// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_hover
 
+#include "AST.h"
 #include "Convert.h"
 
 #include "nixd/Controller/Controller.h"
 
-#include <llvm/Support/Error.h>
-
 #include <boost/asio/post.hpp>
 
-#include <mutex>
+#include <llvm/Support/Error.h>
 
-namespace nixd {
+#include <semaphore>
 
+using namespace nixd;
 using namespace llvm::json;
+using namespace nixf;
 using namespace lspserver;
-using namespace rpc;
+
+namespace {
+
+/// \brief Provide package information, library information ... , from nixpkgs.
+class NixpkgsHoverProvider {
+  AttrSetClient &NixpkgsClient;
+
+  /// \brief Make markdown documentation by package description
+  ///
+  /// FIXME: there are many markdown generation in language server.
+  /// Maybe we can add structured generating first?
+  static std::string mkMarkdown(const PackageDescription &Package) {
+    std::ostringstream OS;
+    // Make each field a new section
+
+    if (Package.Name) {
+      OS << "`" << *Package.Name << "`";
+      OS << "\n";
+    }
+
+    // Make links to homepage.
+    if (Package.Homepage) {
+      OS << "[homepage](" << *Package.Homepage << ")";
+      OS << "\n";
+    }
+
+    if (Package.Description) {
+      OS << "## Description"
+         << "\n\n";
+      OS << *Package.Description;
+      OS << "\n\n";
+
+      if (Package.LongDescription) {
+        OS << "\n\n";
+        OS << *Package.LongDescription;
+        OS << "\n\n";
+      }
+    }
+
+    return OS.str();
+  }
+
+public:
+  NixpkgsHoverProvider(AttrSetClient &NixpkgsClient)
+      : NixpkgsClient(NixpkgsClient) {}
+
+  std::optional<std::string> resolvePackage(std::vector<std::string> Scope,
+                                            std::string Name) {
+    std::binary_semaphore Ready(0);
+    std::optional<PackageDescription> Desc;
+    auto OnReply = [&Ready, &Desc](llvm::Expected<AttrPathInfoResponse> Resp) {
+      if (Resp)
+        Desc = *Resp;
+      else
+        elog("nixpkgs provider: {0}", Resp.takeError());
+      Ready.release();
+    };
+    Scope.emplace_back(std::move(Name));
+    NixpkgsClient.attrpathInfo(Scope, std::move(OnReply));
+    Ready.acquire();
+
+    if (!Desc)
+      return std::nullopt;
+
+    return mkMarkdown(*Desc);
+  }
+};
+
+} // namespace
 
 void Controller::onHover(const TextDocumentPositionParams &Params,
                          Callback<std::optional<Hover>> Reply) {
@@ -33,6 +102,27 @@ void Controller::onHover(const TextDocumentPositionParams &Params,
           return;
         }
         std::string Name = N->name();
+        const VariableLookupAnalysis &VLA = *TU->variableLookup();
+        const ParentMapAnalysis &PM = *TU->parentMap();
+        if (havePackageScope(*N, VLA, PM) && nixpkgsClient()) {
+          // Ask nixpkgs client what's current package documentation.
+          NixpkgsHoverProvider NHP(*nixpkgsClient());
+          auto [Scope, Name] = getScopeAndPrefix(*N, PM);
+          if (std::optional<std::string> Doc =
+                  NHP.resolvePackage(Scope, Name)) {
+            Reply(Hover{
+                .contents =
+                    MarkupContent{
+                        .kind = MarkupKind::Markdown,
+                        .value = std::move(*Doc),
+                    },
+                .range = toLSPRange(N->range()),
+            });
+            return;
+          }
+        }
+        // Reply it's kind by static analysis
+        // FIXME: support more.
         Reply(Hover{
             .contents =
                 MarkupContent{
@@ -46,5 +136,3 @@ void Controller::onHover(const TextDocumentPositionParams &Params,
   };
   boost::asio::post(Pool, std::move(Action));
 }
-
-} // namespace nixd

nixd/tools/nixd/test/hover-package.md

@@ -0,0 +1,83 @@
+# RUN: nixd --lit-test \
+# RUN: --nixpkgs-expr="{ hello.meta.description = \"Very Nice\";  }" \
+# RUN: < %s | FileCheck %s
+
+
+<-- initialize(0)
+
+```json
+{
+   "jsonrpc":"2.0",
+   "id":0,
+   "method":"initialize",
+   "params":{
+      "processId":123,
+      "rootPath":"",
+      "capabilities":{
+      },
+      "trace":"off"
+   }
+}
+```
+
+
+<-- textDocument/didOpen
+
+```json
+{
+   "jsonrpc":"2.0",
+   "method":"textDocument/didOpen",
+   "params":{
+      "textDocument":{
+         "uri":"file:///basic.nix",
+         "languageId":"nix",
+         "version":1,
+         "text":"with pkgs;  hello"
+      }
+   }
+}
+```
+
+<-- textDocument/hover(2)
+
+
+```json
+{
+   "jsonrpc":"2.0",
+   "id":2,
+   "method":"textDocument/hover",
+   "params":{
+      "textDocument":{
+         "uri":"file:///basic.nix"
+      },
+      "position":{
+         "line":0,
+         "character":16
+      }
+   }
+}
+```
+
+```
+     CHECK: "id": 2,
+CHECK-NEXT: "jsonrpc": "2.0",
+CHECK-NEXT: "result": {
+CHECK-NEXT:   "contents": {
+CHECK-NEXT:     "kind": "markdown",
+CHECK-NEXT:     "value": "## Description\n\nVery Nice\n\n"
+CHECK-NEXT:   },
+CHECK-NEXT:   "range": {
+CHECK-NEXT:     "end": {
+CHECK-NEXT:       "character": 17,
+CHECK-NEXT:       "line": 0
+CHECK-NEXT:     },
+CHECK-NEXT:     "start": {
+CHECK-NEXT:       "character": 12,
+CHECK-NEXT:       "line": 0
+CHECK-NEXT:     }
+CHECK-NEXT:   }
+```
+
+```json
+{"jsonrpc":"2.0","method":"exit"}
+```