mesh-build-go: lint directories side by side like the tests, so a large repository's check stays inside its bound (issue 1930)

modules/mesh-build-go/cmd/mesh-build-go/lint.go

@@ -12,6 +12,7 @@ import (
 	"regexp"
 	"sort"
 	"strings"
+	"sync"
 
 	"git.novox.be/novox/mesh-sdk/go/forgekey"
 )
@@ -127,3 +128,45 @@ func (m *Module) lint(ctx context.Context, run forgekey.Runner, tree, d string,
 	}
 	return failed, nil
 }
+
+// lintAll lints each directory, up to m.parallel() at once like the level's tests; the failures join in directory order
+// and the error is the first directory's, so the answer does not depend on which ended first (issue 1930).
+func (m *Module) lintAll(ctx context.Context, run forgekey.Runner, tree string, dirs []string, env func(d string) []string) ([]Failure, error) {
+	type answer struct {
+		failed []Failure
+		err    error
+	}
+	answers := make([]answer, len(dirs))
+	slots := make(chan struct{}, m.parallel())
+	var wg sync.WaitGroup
+	var crash any // a panic of a lint goes on in the caller, as a panic of a test run does
+	var crashMu sync.Mutex
+	for i, d := range dirs {
+		wg.Add(1)
+		slots <- struct{}{}
+		go func() {
+			defer wg.Done()
+			defer func() { <-slots }()
+			defer func() {
+				if p := recover(); p != nil {
+					crashMu.Lock()
+					crash = p
+					crashMu.Unlock()
+				}
+			}()
+			answers[i].failed, answers[i].err = m.lint(ctx, run, tree, d, env(d))
+		}()
+	}
+	wg.Wait()
+	if crash != nil {
+		panic(crash)
+	}
+	var failed []Failure
+	for _, a := range answers {
+		if a.err != nil {
+			return nil, a.err
+		}
+		failed = append(failed, a.failed...)
+	}
+	return failed, nil
+}

modules/mesh-build-go/cmd/mesh-build-go/lint_test.go

@@ -5,7 +5,9 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
+	"sync"
 	"testing"
+	"time"
 
 	"git.novox.be/novox/mesh-sdk/go/forgekey"
 )
@@ -90,3 +92,43 @@ func TestAnUnformattedFileFailsTheUnitLevel(t *testing.T) {
 		}
 	}
 }
+
+// Issue 1930: the lint of many directories runs side by side up to the level's bound, not one after another, and the
+// failures still join in directory order.
+func TestTheLintOfManyDirectoriesRunsAtOnceUpToTheBound(t *testing.T) {
+	files := map[string]string{}
+	var dirs []string
+	for _, d := range []string{"a", "b", "c", "d", "e", "f"} {
+		files[d+"/go.mod"] = "module x/" + d + "\n"
+		files[d+"/x.go"] = "package x\n"
+		dirs = append(dirs, d)
+	}
+	tree := writeTree(t, files)
+	var mu sync.Mutex
+	running, most := 0, 0
+	run := func(ctx context.Context, env []string, name string, args ...string) forgekey.Ran {
+		mu.Lock()
+		running++
+		most = max(most, running)
+		mu.Unlock()
+		time.Sleep(30 * time.Millisecond)
+		mu.Lock()
+		running--
+		mu.Unlock()
+		if strings.HasSuffix(args[1], "b") || strings.HasSuffix(args[1], "e") {
+			return forgekey.Ran{Status: 1, Stderr: "bad " + filepath.Base(args[1])}
+		}
+		return forgekey.Ran{}
+	}
+	m := &Module{Parallel: 3}
+	failed, err := m.lintAll(context.Background(), run, tree, dirs, func(string) []string { return nil })
+	if err != nil {
+		t.Fatal(err)
+	}
+	if most < 2 || most > 3 {
+		t.Errorf("%d lint commands ran at once, want 2 or 3 (the bound)", most)
+	}
+	if len(failed) != 2 || failed[0].Package != "b" || failed[1].Package != "e" {
+		t.Errorf("failed = %+v, want b's then e's", failed)
+	}
+}

modules/mesh-build-go/cmd/mesh-build-go/test.go

@@ -209,13 +209,11 @@ func (m *Module) runLevel(ctx context.Context, tree string, o levelOpts) (*TestR
 		// gofmt and go vet of each directory the level runs come before its tests (ADR 0529 §1; issue 1887 D7-go): a
 		// directory that fails them fails the level at once, and their time is the result's Lint.
 		linted := m.clock()
-		var failed []Failure
-		for _, d := range todo {
-			f, err := m.lint(ctx, run, tree, d, append(m.goEnvFor(filepath.Join(tree, d)), o.env...))
-			if err != nil {
-				return nil, err
-			}
-			failed = append(failed, f...)
+		failed, err := m.lintAll(ctx, run, tree, todo, func(d string) []string {
+			return append(m.goEnvFor(filepath.Join(tree, d)), o.env...)
+		})
+		if err != nil {
+			return nil, err
 		}
 		res.Lint = m.clock().Sub(linted).Seconds()
 		if len(failed) > 0 {