hugofs: Make FileMeta a struct

This commit started out investigating a `concurrent map read write` issue, ending by replacing the map with a struct.

This is easier to reason about, and it's more effective:

```
name                                  old time/op    new time/op    delta
SiteNew/Regular_Deep_content_tree-16    71.5ms ± 3%    69.4ms ± 5%    ~     (p=0.200 n=4+4)

name                                  old alloc/op   new alloc/op   delta
SiteNew/Regular_Deep_content_tree-16    29.7MB ± 0%    27.9MB ± 0%  -5.82%  (p=0.029 n=4+4)

name                                  old allocs/op  new allocs/op  delta
SiteNew/Regular_Deep_content_tree-16      313k ± 0%      303k ± 0%  -3.35%  (p=0.029 n=4+4)
```

See #8749

resources/resource_transformers/js/build.go

@@ -118,7 +118,7 @@ func (t *buildTransformation) Transform(ctx *resources.ResourceTransformationCtx
 				return errors.Errorf("inject: file %q not found", ext)
 			}
 
-			opts.Inject[i] = m.Filename()
+			opts.Inject[i] = m.Filename
 
 		}
 
@@ -150,7 +150,7 @@ func (t *buildTransformation) Transform(ctx *resources.ResourceTransformationCtx
 				fi, err = t.c.sfs.Fs.Stat(path)
 				if err == nil {
 					m := fi.(hugofs.FileMetaInfo).Meta()
-					path = m.Filename()
+					path = m.Filename
 					f, err = m.Open()
 				}
 

resources/resource_transformers/js/options.go

@@ -143,8 +143,8 @@ func loaderFromFilename(filename string) api.Loader {
 	return api.LoaderJS
 }
 
-func resolveComponentInAssets(fs afero.Fs, impPath string) hugofs.FileMeta {
-	findFirst := func(base string) hugofs.FileMeta {
+func resolveComponentInAssets(fs afero.Fs, impPath string) *hugofs.FileMeta {
+	findFirst := func(base string) *hugofs.FileMeta {
 		// This is the most common sub-set of ESBuild's default extensions.
 		// We assume that imports of JSON, CSS etc. will be using their full
 		// name with extension.
@@ -158,7 +158,7 @@ func resolveComponentInAssets(fs afero.Fs, impPath string) hugofs.FileMeta {
 		return nil
 	}
 
-	var m hugofs.FileMeta
+	var m *hugofs.FileMeta
 
 	// First the path as is.
 	fi, err := fs.Stat(impPath)
@@ -217,8 +217,8 @@ func createBuildPlugins(c *Client, opts Options) ([]api.Plugin, error) {
 			// This should be a small number of elements, and when
 			// in server mode, we may get stale entries on renames etc.,
 			// but that shouldn't matter too much.
-			c.rs.JSConfigBuilder.AddSourceRoot(m.SourceRoot())
-			return api.OnResolveResult{Path: m.Filename(), Namespace: nsImportHugo}, nil
+			c.rs.JSConfigBuilder.AddSourceRoot(m.SourceRoot)
+			return api.OnResolveResult{Path: m.Filename, Namespace: nsImportHugo}, nil
 		}
 
 		// Fall back to ESBuild's resolve.

resources/resource_transformers/postcss/postcss.go

@@ -394,7 +394,7 @@ func (imp *importResolver) toFileError(output string) error {
 	if err != nil {
 		return inErr
 	}
-	realFilename := fi.(hugofs.FileMetaInfo).Meta().Filename()
+	realFilename := fi.(hugofs.FileMetaInfo).Meta().Filename
 
 	ferr := herrors.NewFileError("css", -1, file.Offset+1, 1, inErr)
 

resources/resource_transformers/tocss/dartsass/transform.go

@@ -90,7 +90,7 @@ func (t *transform) Transform(ctx *resources.ResourceTransformationCtx) error {
 	for _, ip := range opts.IncludePaths {
 		info, err := t.c.workFs.Stat(filepath.Clean(ip))
 		if err == nil {
-			filename := info.(hugofs.FileMetaInfo).Meta().Filename()
+			filename := info.(hugofs.FileMetaInfo).Meta().Filename
 			args.IncludePaths = append(args.IncludePaths, filename)
 		}
 	}
@@ -191,7 +191,7 @@ func (t importResolver) CanonicalizeURL(url string) (string, error) {
 		fi, err := t.c.sfs.Fs.Stat(filenameToCheck)
 		if err == nil {
 			if fim, ok := fi.(hugofs.FileMetaInfo); ok {
-				return "file://" + filepath.ToSlash(fim.Meta().Filename()), nil
+				return "file://" + filepath.ToSlash(fim.Meta().Filename), nil
 			}
 		}
 	}

resources/resource_transformers/tocss/scss/tocss.go

@@ -55,7 +55,7 @@ func (t *toCSSTransformation) Transform(ctx *resources.ResourceTransformationCtx
 	for _, ip := range options.from.IncludePaths {
 		info, err := t.c.workFs.Stat(filepath.Clean(ip))
 		if err == nil {
-			filename := info.(hugofs.FileMetaInfo).Meta().Filename()
+			filename := info.(hugofs.FileMetaInfo).Meta().Filename
 			options.to.IncludePaths = append(options.to.IncludePaths, filename)
 		}
 	}
@@ -105,7 +105,7 @@ func (t *toCSSTransformation) Transform(ctx *resources.ResourceTransformationCtx
 			fi, err := t.c.sfs.Fs.Stat(filenameToCheck)
 			if err == nil {
 				if fim, ok := fi.(hugofs.FileMetaInfo); ok {
-					return fim.Meta().Filename(), "", true
+					return fim.Meta().Filename, "", true
 				}
 			}
 		}