formatter: add drop_merge_tag option

Add an option to drop the `!!merge` tag from all formatted yaml. Also
add a test for IndentlessArrays that should have already been there and
fixed the pre-commit description which should have been fixed before
too.

.pre-commit-hooks.yaml

@@ -1,6 +1,6 @@
 - id: yamlfmt
   name: yamlfmt 
-  description: This hook uses github.com/google/yamlfmt to format yaml files. Requires golang >1.18 to be installed.
+  description: This hook uses github.com/google/yamlfmt to format yaml files. Requires golang >1.20 to be installed.
   entry: yamlfmt
   language: golang
   types: [yaml]

docs/config-file.md

@@ -56,6 +56,7 @@ The basic formatter is a barebones formatter that simply takes the data provided
 | `max_line_length`        | int            | 0       | Set the maximum line length (see notes below). if not set, defaults to 0 which means no limit. |
 | `scan_folded_as_literal` | bool           | false   | Option that will preserve newlines in folded block scalars (blocks that start with `>`). |
 | `indentless_arrays`      | bool           | false   | Render `-` array items (block sequence items) without an increased indent. |
+| `drop_merge_tag`         | bool           | false   | Assume that any well formed merge using just a `<<` token will be a merge, and drop the `!!merge` tag from the formatted result. |
 
 ### Note on `max_line_length`
 

formatters/basic/config.go

@@ -29,6 +29,7 @@ type Config struct {
 	DisallowAnchors      bool                   `mapstructure:"disallow_anchors"`
 	ScanFoldedAsLiteral  bool                   `mapstructure:"scan_folded_as_literal"`
 	IndentlessArrays     bool                   `mapstructure:"indentless_arrays"`
+	DropMergeTag         bool                   `mapstructure:"drop_merge_tag"`
 }
 
 func DefaultConfig() *Config {

formatters/basic/formatter.go

@@ -108,6 +108,7 @@ func (f *BasicFormatter) getNewEncoder(buf *bytes.Buffer) *yaml.Encoder {
 	e.SetExplicitDocumentStart(f.Config.IncludeDocumentStart)
 	e.SetAssumeBlockAsLiteral(f.Config.ScanFoldedAsLiteral)
 	e.SetIndentlessBlockSequence(f.Config.IndentlessArrays)
+	e.SetDropMergeTag(f.Config.DropMergeTag)
 
 	return e
 }

formatters/basic/formatter_test.go

@@ -231,3 +231,41 @@ func TestScanFoldedAsLiteral(t *testing.T) {
 		t.Fatalf("expected string to be %d lines, was %d", lines, resultLines)
 	}
 }
+
+func TestIndentlessArrays(t *testing.T) {
+	config := basic.DefaultConfig()
+	config.IndentlessArrays = true
+	f := newFormatter(config)
+
+	yml := `a:
+- 1
+- 2
+`
+	result, err := f.Format([]byte(yml))
+	if err != nil {
+		t.Fatalf("expected formatting to pass, returned error: %v", err)
+	}
+	resultStr := string(result)
+	if resultStr != yml {
+		t.Fatalf("expected:\n%s\ngot:\n%s", yml, resultStr)
+	}
+}
+
+func TestDropMergeTag(t *testing.T) {
+	config := basic.DefaultConfig()
+	config.DropMergeTag = true
+	f := newFormatter(config)
+
+	yml := `a: &a
+b:
+  <<: *a`
+
+	result, err := f.Format([]byte(yml))
+	if err != nil {
+		t.Fatalf("expected formatting to pass, returned error: %v", err)
+	}
+	resultStr := string(result)
+	if strings.Contains(resultStr, "!!merge") {
+		t.Fatalf("expected formatted result to drop merge tag, was found:\n%s", resultStr)
+	}
+}

go.mod

@@ -5,7 +5,7 @@ go 1.20
 require (
 	github.com/RageCage64/multilinediff v0.2.0
 	github.com/bmatcuk/doublestar/v4 v4.6.0
-	github.com/braydonk/yaml v0.5.0
+	github.com/braydonk/yaml v0.6.0
 	github.com/mitchellh/mapstructure v1.5.0
 )
 

go.sum

@@ -8,6 +8,8 @@ github.com/braydonk/yaml v0.4.0 h1:MNjdriecuspytC31J7Tzx6O8b1yAbMSTGvRG6vLSXZc=
 github.com/braydonk/yaml v0.4.0/go.mod h1:hcm3h581tudlirk8XEUPDBAimBPbmnL0Y45hCRl47N4=
 github.com/braydonk/yaml v0.5.0 h1:j1SlSSD9JLRKgkmFb66hsDH4D0YFlLOLXSXDwNH9/LU=
 github.com/braydonk/yaml v0.5.0/go.mod h1:hcm3h581tudlirk8XEUPDBAimBPbmnL0Y45hCRl47N4=
+github.com/braydonk/yaml v0.6.0 h1:nHt2AzmV4yMhXSNROksvkTgAxzollgy7uVOKfCVXhMo=
+github.com/braydonk/yaml v0.6.0/go.mod h1:hcm3h581tudlirk8XEUPDBAimBPbmnL0Y45hCRl47N4=
 github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
 github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/mitchellh/mapstructure v1.5.0 h1:jeMsZIYE/09sWLaz43PL7Gy6RuMjD2eJVyuac5Z2hdY=