convert file ext to lowercase for format detection (#2121)

* convert file ext to lowercase for format detection

To ensure proper file format detection with case-insensitive file
systems.

* use filepath.Ext for more reliable file ext detection

especially for paths like index.js/foo

* add a test for file ext based format detection

pkg/yqlib/format.go

@@ -2,6 +2,7 @@ package yqlib
 
 import (
  "fmt"
+ "path/filepath"
  "strings"
 )
 
@@ -107,12 +108,11 @@ func (f *Format) GetConfiguredEncoder() Encoder {
 }
 
 func FormatStringFromFilename(filename string) string {
-
  if filename != "" {
- GetLogger().Debugf("checking file extension '%s' for auto format detection", filename)
- nPos := strings.LastIndex(filename, ".")
- if nPos > -1 {
- format := filename[nPos+1:]
+ GetLogger().Debugf("checking filename '%s' for auto format detection", filename)
+ ext := filepath.Ext(filename)
+ if ext != "" && ext[0] == '.' {
+ format := strings.ToLower(ext[1:])
  GetLogger().Debugf("detected format '%s'", format)
  return format
  }

pkg/yqlib/format_test.go

@@ -50,3 +50,13 @@ func TestFormatFromString(t *testing.T) {
  }
  }
 }
+
+func TestFormatStringFromFilename(t *testing.T) {
+ test.AssertResult(t, "yaml", FormatStringFromFilename("test.Yaml"))
+ test.AssertResult(t, "yaml", FormatStringFromFilename("test.index.Yaml"))
+ test.AssertResult(t, "yaml", FormatStringFromFilename("test"))
+ test.AssertResult(t, "json", FormatStringFromFilename("test.json"))
+ test.AssertResult(t, "json", FormatStringFromFilename("TEST.JSON"))
+ test.AssertResult(t, "yaml", FormatStringFromFilename("test.json/foo"))
+ test.AssertResult(t, "yaml", FormatStringFromFilename(""))
+}