Unify host and native filesystem acquisition

internal/engine/source.go

@@ -22,6 +22,7 @@ type Source struct {
 	kind      sourceKind
 	path      string
 	label     string
+	namespace *nativeNamespace
 	data      []byte
 	reader    *readerSource
 	createErr sourceCreationError
@@ -32,6 +33,7 @@ type sourceKind uint8
 const (
 	sourceInvalid sourceKind = iota
 	sourceFile
+	sourceFilesystem
 	sourceBytes
 	sourceReader
 	sourceNone
@@ -60,6 +62,13 @@ func File(path string) Source {
 	return Source{kind: sourceFile, path: path, label: path}
 }
 
+func filesystemFile(namespace *nativeNamespace, name string) Source {
+	if namespace == nil || namespace.filesystem == nil || name == "." || !fs.ValidPath(name) {
+		return Source{kind: sourceFilesystem, createErr: creationInvalidPath}
+	}
+	return Source{kind: sourceFilesystem, path: name, label: namespace.label + "/" + name, namespace: namespace}
+}
+
 // Bytes snapshots data immediately. Label must be nonempty and safe to display;
 // constructor problems are reported when the source is consumed.
 func Bytes(label string, data []byte) Source {
@@ -143,6 +152,18 @@ func readSource(source Source, sourceID string, limits sourceLimits) (sourceRead
 			return sourceRead{info: info}, []Diagnostic{sourceReadDiagnostic(failure, sourceID, CodeSourceLimitExceeded, "source exceeds the configured byte limit")}
 		}
 		return sourceRead{data: bytes.Clone(data), info: info}, nil
+	case sourceFilesystem:
+		access := newNativeAccess(source.namespace.filesystem, ".", source.namespace.token)
+		info.Path = source.path
+		canonical, err := access.canonical(source.path)
+		if err != nil {
+			return sourceRead{info: info}, []Diagnostic{classifySourceError(err, sourceID)}
+		}
+		data, failure := readRegularFile(canonical, access.stat, access.open, limit)
+		if failure != nil {
+			return sourceRead{info: info}, []Diagnostic{sourceReadDiagnostic(failure, sourceID, CodeSourceLimitExceeded, "source exceeds the configured byte limit")}
+		}
+		return sourceRead{data: bytes.Clone(data), info: info}, nil
 	case sourceBytes:
 		input = bytes.NewReader(source.data)
 	case sourceReader: