Clarify filesystem directive and override ownership

filesystem.go

@@ -0,0 +1,121 @@
+package configkit
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+func validateFilesystemContext(source Source, context *FilesystemContext, main parsedSource) *Diagnostic {
+	rootPath, _, _, diagnostic := importFilesystem(source, context, main)
+	if diagnostic != nil {
+		return diagnostic
+	}
+	root, err := os.OpenRoot(rootPath)
+	if err != nil {
+		value := globFilesystemDiagnostic(err, "configuration root could not be opened", Location{})
+		value.Primary = nil
+		return &value
+	}
+	if err := root.Close(); err != nil {
+		value := importDiagnostic(CodeImportRead, "configuration root could not be closed", nil)
+		return &value
+	}
+	return nil
+}
+
+func filesystemOptionDiagnostics(source Source, context *FilesystemContext) []Diagnostic {
+	switch source.kind {
+	case sourceNone:
+		return []Diagnostic{optionDiagnostic(CodeOptionsInvalid, "NoSource cannot use filesystem context")}
+	case sourceFile:
+		if context.BaseDir != "" {
+			return []Diagnostic{optionDiagnostic(CodeOptionsInvalid, "file sources determine their own import base directory")}
+		}
+	case sourceBytes, sourceReader:
+		if context.BaseDir == "" || context.Root == "" {
+			return []Diagnostic{optionDiagnostic(CodeOptionsInvalid, "byte and reader filesystem context requires base and root directories")}
+		}
+		if !filepath.IsAbs(context.BaseDir) || !filepath.IsAbs(context.Root) {
+			return []Diagnostic{optionDiagnostic(CodeOptionsInvalid, "byte and reader filesystem base and root directories must be absolute")}
+		}
+	}
+	return nil
+}
+
+func importFilesystem(source Source, context *FilesystemContext, main parsedSource) (rootPath, basePath, mainPath string, diagnostic *Diagnostic) {
+	if main.source == nil || main.document == nil {
+		value := importDiagnostic(CodeImportInvalid, "imports require a selected configuration source", nil)
+		return "", "", "", &value
+	}
+
+	if source.kind == sourceFile {
+		if context != nil && context.BaseDir != "" {
+			value := optionDiagnostic(CodeOptionsInvalid, "file sources determine their own import base directory")
+			return "", "", "", &value
+		}
+		canonical, err := canonicalExistingPath(source.path)
+		if err != nil {
+			value := importDiagnostic(CodeImportInvalid, "selected source path could not be canonicalized", nil)
+			return "", "", "", &value
+		}
+		mainPath = canonical
+		basePath = filepath.Dir(canonical)
+		rootPath = basePath
+		if context != nil && context.Root != "" {
+			rootPath, err = canonicalExistingPath(context.Root)
+			if err != nil {
+				value := importDiagnostic(CodeImportInvalid, "configuration root could not be canonicalized", nil)
+				return "", "", "", &value
+			}
+		}
+	} else {
+		if context == nil || context.BaseDir == "" || context.Root == "" {
+			value := optionDiagnostic(CodeOptionsInvalid, "byte and reader imports require absolute base and root directories")
+			return "", "", "", &value
+		}
+		if !filepath.IsAbs(context.BaseDir) || !filepath.IsAbs(context.Root) {
+			value := optionDiagnostic(CodeOptionsInvalid, "byte and reader import base and root directories must be absolute")
+			return "", "", "", &value
+		}
+		var err error
+		basePath, err = canonicalExistingPath(context.BaseDir)
+		if err != nil {
+			value := importDiagnostic(CodeImportInvalid, "import base directory could not be canonicalized", nil)
+			return "", "", "", &value
+		}
+		rootPath, err = canonicalExistingPath(context.Root)
+		if err != nil {
+			value := importDiagnostic(CodeImportInvalid, "configuration root could not be canonicalized", nil)
+			return "", "", "", &value
+		}
+	}
+	if !containedPath(rootPath, basePath) || (mainPath != "" && !containedPath(rootPath, mainPath)) {
+		value := importDiagnostic(CodeImportOutsideRoot, "selected source and import base must stay inside the configuration root", nil)
+		return "", "", "", &value
+	}
+	for _, candidate := range []string{rootPath, basePath} {
+		info, err := os.Stat(candidate)
+		if err != nil || !info.IsDir() {
+			value := importDiagnostic(CodeImportInvalid, "configuration root and import base must be directories", nil)
+			return "", "", "", &value
+		}
+	}
+	return rootPath, basePath, mainPath, nil
+}
+
+func canonicalExistingPath(name string) (string, error) {
+	absolute, err := filepath.Abs(name)
+	if err != nil {
+		return "", err
+	}
+	return filepath.EvalSymlinks(filepath.Clean(absolute))
+}
+
+func containedPath(root, target string) bool {
+	relative, err := filepath.Rel(root, target)
+	if err != nil || filepath.IsAbs(relative) {
+		return false
+	}
+	return relative != ".." && !strings.HasPrefix(relative, ".."+string(filepath.Separator))
+}