nix-env --query: Respect --drv-path with --json

```json
{
  "AMB-plugins": {
    "drvPath": "/nix/store/l99cb7h2hy8dg005arsjbd9kx0w05d3h-AMB-plugins-0.8.1.drv",
    "name": "AMB-plugins-0.8.1",
    "outputName": "out",
    "outputs": {
      "out": null
    },
    "pname": "AMB-plugins",
    "system": "x86_64-linux",
    "version": "0.8.1"
  },
  "ArchiSteamFarm": {
    "drvPath": "/nix/store/nhplgyjj34fz6hjmnyih25gxscfh8s7b-ArchiSteamFarm-5.4.12.5.drv",
    "name": "ArchiSteamFarm-5.4.12.5",
    "outputName": "out",
    "outputs": {
      "out": null
    },
    "pname": "ArchiSteamFarm",
    "system": "x86_64-linux",
    "version": "5.4.12.5"
  },
...
```

doc/manual/src/release-notes/rl-next.md

@@ -12,6 +12,8 @@
 
 - Introduce a new built-in function [`builtins.convertHash`](@docroot@/language/builtins.md#builtins-convertHash).
 
+- `nix-env --query` now respects `--drv-path` with `--json`.
+
 - `nix-shell` shebang lines now support single-quoted arguments.
 
 - `builtins.fetchTree` is now marked as stable.

src/nix-env/nix-env.cc

@@ -922,7 +922,7 @@ static VersionDiff compareVersionAgainstSet(
 }
 
 
-static void queryJSON(Globals & globals, std::vector<DrvInfo> & elems, bool printOutPath, bool printMeta)
+static void queryJSON(Globals & globals, std::vector<DrvInfo> & elems, bool printOutPath, bool printDrvPath, bool printMeta)
 {
     using nlohmann::json;
     json topObj = json::object();
@@ -953,6 +953,11 @@ static void queryJSON(Globals & globals, std::vector<DrvInfo> & elems, bool prin
                 }
             }
 
+            if (printDrvPath) {
+                auto drvPath = i.queryDrvPath();
+                if (drvPath) pkgObj["drvPath"] = globals.state->store->printStorePath(*drvPath);
+            }
+
             if (printMeta) {
                 json &metaObj = pkgObj["meta"];
                 metaObj = json::object();
@@ -1079,7 +1084,7 @@ static void opQuery(Globals & globals, Strings opFlags, Strings opArgs)
 
     /* Print the desired columns, or XML output. */
     if (jsonOutput) {
-        queryJSON(globals, elems, printOutPath, printMeta);
+        queryJSON(globals, elems, printOutPath, printDrvPath, printMeta);
         cout << '\n';
         return;
     }

tests/functional/user-envs.sh

@@ -26,6 +26,7 @@ nix-env -f ./user-envs.nix -qa --json --out-path | jq -e '.[] | select(.name ==
     .outputName == "out",
     (.outputs.out | test("'$NIX_STORE_DIR'.*-0\\.1"))
 ] | all'
+nix-env -f ./user-envs.nix -qa --json --drv-path | jq -e '.[] | select(.name == "bar-0.1") | (.drvPath | test("'$NIX_STORE_DIR'.*-0\\.1\\.drv"))'
 
 # Query descriptions.
 nix-env -f ./user-envs.nix -qa '*' --description | grepQuiet silly