nix-eval-jobs: --apply

Based off of https://github.com/NixOS/nix-eval-jobs/pull/332 and
9f292a402a6edf620b872bedaaad5f0a45c23826

closes https://git.lix.systems/lix-project/lix/issues/1214

Co-authored-by: Mic92 <joerg@thalheim.io>
Co-authored-by: Yannik Sander <yannik@floxdev.com>
Change-Id: Ifba7081b384d18fbdc47437de261d30b65a7930a
(cherry picked from commit 405ff2eb03)

doc/manual/change-authors.yml

@@ -315,5 +315,8 @@ yorickvp:
 yshui:
   github: yshui
 
+ysndr:
+  github: ysndr
+
 zimbatm:
   github: zimbatm

doc/manual/rl-next/nej-apply-flag.md

@@ -0,0 +1,12 @@
+---
+synopsis: "nix-eval-jobs support `--apply` flag"
+cls: [5748]
+category: "Features"
+credits: [isabelroses,mic92,ysndr]
+issues: [fj#1214]
+---
+
+`nix-eval-jobs` now supports the `--apply` flag. With this you can apply the
+provided function to the each derivation, the result of this function will then
+be serialized as a JSON value and stored inside `"extraValue"` key of the json
+line output.

subprojects/nix-eval-jobs/README.md

@@ -46,6 +46,7 @@ executable.
 $ nix-eval-jobs --help
 USAGE: nix-eval-jobs [options] expr
 
+  --apply                Apply provided Nix function to each derivation. The result of this function will be serialized as a JSON value and stored inside `"extraValue"` key of the json line output.
   --arg                  Pass the value *expr* as the argument *name* to Nix functions.
   --argstr               Pass the string *string* as the argument *name* to Nix functions.
   --check-cache-status   Check if the derivations are present locally or in any configured substituters (i.e. binary cache). The information will be exposed in the `isCached` field of the JSON output.

subprojects/nix-eval-jobs/src/eval-args.cc

@@ -12,7 +12,8 @@
 
 #include "eval-args.hh"
 
-MyArgs::MyArgs(nix::AsyncIoRoot & aio) : MixCommonArgs("nix-eval-jobs"), aio_(aio) {
+MyArgs::MyArgs(nix::AsyncIoRoot &aio)
+    : MixCommonArgs("nix-eval-jobs"), aio_(aio) {
     addFlag({
         .longName = "help",
         .description = "show usage information",
@@ -22,7 +23,8 @@ MyArgs::MyArgs(nix::AsyncIoRoot & aio) : MixCommonArgs("nix-eval-jobs"), aio_(ai
                 if (flag->hidden || hiddenCategories.count(flag->category)) {
                     continue;
                 }
-                std::cout << nix::fmt("  --%-20s %s\n", name, flag->description);
+                std::cout << nix::fmt("  --%-20s %s\n", name,
+                                      flag->description);
             }
             ::exit(0);
         }},
@@ -105,6 +107,14 @@ MyArgs::MyArgs(nix::AsyncIoRoot & aio) : MixCommonArgs("nix-eval-jobs"), aio_(ai
              .description = "treat the argument as a Nix expression",
              .handler = {&fromArgs, true}});
 
+    addFlag({.longName = "apply",
+             .description =
+                 "Apply provided Nix function to each derivation. The result "
+                 "of this function will be serialized as a JSON value and "
+                 "stored inside `\"extraValue\"` key of the json line output.",
+             .labels = {"expr"},
+             .handler = {&applyExpr}});
+
     // usually in MixFlakeOptions
     addFlag({
         .longName = "override-input",

subprojects/nix-eval-jobs/src/eval-args.hh

@@ -22,6 +22,7 @@ struct MyArgs : virtual public nix::MixEvalArgs,
 
     bool worker = false;
     std::string releaseExpr;
+    std::string applyExpr;
     nix::Path gcRootsDir;
     bool flake = false;
     bool fromArgs = false;

subprojects/nix-eval-jobs/src/worker.cc

@@ -28,6 +28,7 @@
 #include <lix/libexpr/symbol-table.hh>
 #include <lix/libutil/types.hh>
 #include <lix/libexpr/value.hh>
+#include <lix/libexpr/value-to-json.hh>
 #include <lix/libutil/terminal.hh>
 #include <exception>
 #include <numeric>
@@ -201,6 +202,21 @@ try {
                         maybeConstituents =
                             readConstituents(&v, state, evaluator);
                     }
+                    if (args.applyExpr != "") {
+                        nix::Expr &applyExpr = state->ctx.parseExprFromString(
+                            args.applyExpr, nix::CanonPath::fromCwd());
+
+                        nix::Value vApply = state->eval(applyExpr);
+                        nix::Value vRes =
+                            state->callFunction(vApply, v, nix::noPos);
+                        state->forceAttrs(
+                            vRes, nix::noPos,
+                            "apply needs to evaluate to an attrset");
+
+                        nix::NixStringContext context;
+                        reply["extraValue"] = nix::printValueAsJSON(
+                            *state, true, vRes, nix::noPos, context);
+                    }
                     auto drv = Drv(attrPathS, *state, *drvInfo, args,
                                    maybeConstituents);
                     reply.update(drv);

subprojects/nix-eval-jobs/tests/test_eval.py

@@ -124,6 +124,45 @@ def test_eval_error() -> None:
         assert "this is an evaluation error" in attr["error"]
 
 
+def test_apply() -> None:
+    with TemporaryDirectory() as tempdir:
+        applyExpr = """drv: {
+            the-name = drv.name;
+            version = drv.version or null;
+        }"""
+
+        results, _ = evaluate(
+            tempdir,
+            0,
+            ["--workers", "1", "--apply", applyExpr, "--flake", ".#hydraJobs"],
+        )
+
+        assert len(results) == 4  # sanity check that we assert against all jobs
+
+        # Check that nix-eval-jobs applied the expression correctly,
+        # exposing the result under the `extraValue` key, and extracted
+        # 'version' as 'version' and 'name' as 'the-name'
+        dotted_job = results[0]
+        assert dotted_job["attr"] == '"dotted.attr"'
+        assert dotted_job["extraValue"]["the-name"].startswith("hello-")
+        assert dotted_job["extraValue"]["version"] is not None
+
+        built_job = results[1]
+        assert built_job["attr"] == "builtJob"
+        assert built_job["extraValue"]["the-name"] == "job1"
+        assert built_job["extraValue"]["version"] is None
+
+        recurse_drv = results[2]
+        assert recurse_drv["attr"] == "recurse.drvB"
+        assert recurse_drv["extraValue"]["the-name"] == "drvB"
+        assert recurse_drv["extraValue"]["version"] is None
+
+        substituted_job = results[3]
+        assert substituted_job["attr"] == "substitutedJob"
+        assert substituted_job["extraValue"]["the-name"].startswith("hello-")
+        assert substituted_job["extraValue"]["version"] is not None
+
+
 @pytest.mark.infiniterecursion
 def test_recursion_error() -> None:
     with TemporaryDirectory() as tempdir: