Answer architecture round 10: the paired ruling at fb2c809 is better; a mounted module names its manifest from its files' root, and the mount wrapper returns nothing beside an error

docs/comprehension-history.md

@@ -449,3 +449,26 @@ Inherited architect, decided by:
 - Navigation: `data/svse/fs.go:1` `svse`: the step from a dot path to a folder goes through the lowered-namespace rule, stated only in the README and each package doc
 - Navigation: `internal/datafiles/datafiles.go:57` `labelled`: errors name sv_SE (address.json), not a path that opens as written
 - Locality: `fejkdata.go:99` `New`: New loads exactly its options, cancelled by `data/svse/fs.go:1`'s dependency on geose that nothing in Go expresses
+
+## 2026-10-11T13:08:34Z, PR #203 at fb2c809, against bf1becb
+
+Ruling: better
+
+| Seat | Navigation | Locality | Shape | Self-sufficiency | Overall |
+|---|---|---|---|---|---|
+| Mid A | same | better | same | same | better |
+| Inherited architect | better | better | same | better | better |
+
+Mid A, decided by:
+
+- Locality, Overall: `fejkdata.go:66` `WithDataFS`: the caller names every module and New refuses no data naming the fix, where the base prepended a package-level shippedSource behind config{shipped: true}
+- Locality: `data/sv_SE/fs.go:19` `Modules`: sv_SE reading geo.SE is a Go import with a doc line, not only a template reference inside address.json
+- Shape: `internal/datafiles/mount.go:13` `mounted`: a hand-built virtual fs.FS replaces a base string, balanced by Source losing a field and Walk, Load and Manifest turning path-agnostic
+
+Inherited architect, decided by:
+
+- Locality, Navigation, Overall: `data/sv_SE/fs.go:19` `Modules`: a locale reading its country's places is a Go import, one hop in code where the base needed the README or a trace through JSON references
+- Locality, Self-sufficiency: `fejkdata.go:66` `WithDataFS`: every source is named at the call site, and leaving them all out gives an error that spells the fix
+- Navigation: `data/modules.go:17` `Modules`: shipped data has a Go home inside data/, each module's manifest beside its files
+- Shape: `internal/datafiles/mount.go:13` `mounted`: seven small types fake the folders above the mount, balanced by Source keeping one form and truthful per-module packages
+- Self-sufficiency: `data/sv_SE/fs.go:1` `svse`: each module says in code which namespace it supplies and what it reads

imports_test.go

@@ -38,7 +38,7 @@ func TestPackageImports(t *testing.T) {
 		"data/misc":            nil,
 		"data/sv_SE":           {"data/geo/SE"},
 		"internal/builtinfunc": {"internal/datatype", "internal/drawstate", "internal/grammar", "internal/invariant", "internal/proven"},
-		"internal/datafiles":   {"internal/grammar", "internal/invariant", "internal/jsonvalue"},
+		"internal/datafiles":   {"internal/grammar", "internal/jsonvalue"},
 		"internal/datatype":    nil,
 		"internal/drawstate":   nil,
 		"internal/grammar":     nil,

internal/datafiles/manifest.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"io/fs"
+	"path"
 	"sort"
 	"strings"
 
@@ -49,7 +50,12 @@ func (s Source) Manifest() (Manifest, error) {
 }
 
 // ManifestPath is the manifest's path as errors name it.
-func (s Source) ManifestPath() string { return s.labelled(ManifestFile) }
+func (s Source) ManifestPath() string {
+	if m, isMounted := s.fsys.(mounted); isMounted {
+		return s.labelled(path.Join(m.at, ManifestFile))
+	}
+	return s.labelled(ManifestFile)
+}
 
 // decodeManifest decodes a manifest, refusing any key or shape it does not define, and
 // reports every mistake: first each entry's own, in path order, then each parent naming

internal/datafiles/mount.go

@@ -22,7 +22,10 @@ func (m mounted) Open(name string) (fs.File, error) {
 	}
 	if ok {
 		f, err := m.fsys.Open(".")
-		return mountRoot{File: f, name: path.Base(name)}, err
+		if err != nil {
+			return nil, err
+		}
+		return mountRoot{File: f, name: path.Base(name)}, nil
 	}
 	if next, ok := m.towards(name); ok {
 		return &mountDir{name: path.Base(name), next: next}, nil
@@ -70,7 +73,10 @@ type mountRoot struct {
 
 func (r mountRoot) Stat() (fs.FileInfo, error) {
 	info, err := r.File.Stat()
-	return renamed{FileInfo: info, name: r.name}, err
+	if err != nil {
+		return nil, err
+	}
+	return renamed{FileInfo: info, name: r.name}, nil
 }
 
 func (r mountRoot) ReadDir(n int) ([]fs.DirEntry, error) {