chore: import upstream snapshot with attribution

parser/source.go

@@ -0,0 +1,45 @@
+package parser
+
+import (
+	"fmt"
+	"path/filepath"
+
+	"github.com/kashav/fsql/tokenizer"
+)
+
+// parseSourceList parses the list of directories passed to the FROM clause. If
+// a source is followed by the AS keyword, the following word is registered as
+// an alias.
+func (p *parser) parseSourceList(sources *map[string][]string,
+	aliases *map[string]string) error {
+	for {
+		// If the next token is a hypen, exclude this directory.
+		sourceType := "include"
+		if token := p.expect(tokenizer.Hyphen); token != nil {
+			sourceType = "exclude"
+		}
+
+		source := p.expect(tokenizer.Identifier)
+		if source == nil {
+			return p.currentError()
+		}
+		source.Raw = filepath.Clean(source.Raw)
+		(*sources)[sourceType] = append((*sources)[sourceType], source.Raw)
+
+		if token := p.expect(tokenizer.As); token != nil {
+			alias := p.expect(tokenizer.Identifier)
+			if alias == nil {
+				return p.currentError()
+			}
+			if sourceType == "exclude" {
+				return fmt.Errorf("cannot alias excluded directory %s", source.Raw)
+			}
+			(*aliases)[alias.Raw] = source.Raw
+		}
+
+		if p.expect(tokenizer.Comma) == nil {
+			break
+		}
+	}
+	return nil
+}