Avoid decoding unrelated profiles

internal/profile/repository_test.go

@@ -4,9 +4,11 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"strings"
+	"sync"
 	"testing"
 	"testing/fstest"
 
@@ -720,6 +722,70 @@ unknown: true
 	}
 }
 
+func TestProfileRepositoryReadsSourcesFreshOnEveryLookup(t *testing.T) {
+	newSource := func() (*recordingProfileFS, Repository) {
+		fsys := &recordingProfileFS{FS: fstest.MapFS{
+			"target.yaml": profileMapFile(`
+id: target
+endpoint: http://localhost:8000/v1
+model: target-model
+`),
+			"unrelated.yaml": profileMapFile(`
+id: unrelated
+endpoint: http://localhost:8000/v1
+model: unrelated-model
+`),
+		}}
+		return fsys, NewFSRepository(fsys, ".")
+	}
+
+	t.Run("selected source", func(t *testing.T) {
+		fsys, repo := newSource()
+		for lookup := 1; lookup <= 2; lookup++ {
+			got, err := repo.GetProfile(context.Background(), "target")
+			if err != nil {
+				t.Fatalf("lookup %d: %v", lookup, err)
+			}
+			if got.Model != "target-model" {
+				t.Fatalf("lookup %d model = %q", lookup, got.Model)
+			}
+			for _, name := range []string{"target.yaml", "unrelated.yaml"} {
+				if count := fsys.openCount(name); count != lookup {
+					t.Fatalf("%s opens after lookup %d = %d, want %d", name, lookup, count, lookup)
+				}
+			}
+		}
+	})
+
+	t.Run("overlay fallthrough", func(t *testing.T) {
+		primaryFS := &recordingProfileFS{FS: fstest.MapFS{
+			"unrelated.yaml": profileMapFile(`
+id: unrelated
+endpoint: http://localhost:8000/v1
+model: unrelated-model
+`),
+		}}
+		fallbackFS, fallback := newSource()
+		repo := NewOverlayRepository(NewFSRepository(primaryFS, "."), fallback)
+
+		for lookup := 1; lookup <= 2; lookup++ {
+			got, err := repo.GetProfile(context.Background(), "target")
+			if err != nil {
+				t.Fatalf("lookup %d: %v", lookup, err)
+			}
+			if got.Model != "target-model" {
+				t.Fatalf("lookup %d model = %q", lookup, got.Model)
+			}
+			if count := primaryFS.openCount("unrelated.yaml"); count != lookup {
+				t.Fatalf("primary opens after lookup %d = %d, want %d", lookup, count, lookup)
+			}
+			if count := fallbackFS.openCount("target.yaml"); count != lookup {
+				t.Fatalf("fallback opens after lookup %d = %d, want %d", lookup, count, lookup)
+			}
+		}
+	})
+}
+
 func TestProfileRepositoriesRejectInvalidExecutionSettings(t *testing.T) {
 	ctx := context.Background()
 
@@ -849,6 +915,31 @@ type profileRepositorySource struct {
 	newRepository func(t *testing.T, files map[string]string) Repository
 }
 
+type recordingProfileFS struct {
+	fs.FS
+	mu     sync.Mutex
+	opened []string
+}
+
+func (f *recordingProfileFS) Open(name string) (fs.File, error) {
+	f.mu.Lock()
+	f.opened = append(f.opened, name)
+	f.mu.Unlock()
+	return f.FS.Open(name)
+}
+
+func (f *recordingProfileFS) openCount(name string) int {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	count := 0
+	for _, opened := range f.opened {
+		if opened == name {
+			count++
+		}
+	}
+	return count
+}
+
 func profileRepositorySources() []profileRepositorySource {
 	return []profileRepositorySource{
 		{