Add group_prefixes option.

README.md

@@ -227,6 +227,47 @@ allows for sorting data such as Go structs and JSON objects.
 > Note: angle brackets (`<` and `>`) are not supported by block mode due to
 > being used for mathematical expressions in an unbalanced format.
 
+#### Custom grouping
+
+Another way to group lines together is with the `group_prefixes` argument. This
+takes a comma-separated list of prefixes. Any line beginning with one of those
+prefixes will be treated as a continuation line.
+
+<table border="0">
+<tr>
+<td>
+
+```
+
+spaghetti
+with meatballs
+peanut butter
+and jelly
+hamburger
+with lettuce
+and tomatoes
+
+```
+
+</td>
+<td>
+
+```diff
++// keep-sorted start group_prefixes=and,with
+ hamburger
+ with lettuce
+ and tomatoes
+ peanut butter
+ and jelly
+ spaghetti
+ with meatballs
++// keep-sorted end
+```
+
+</td>
+</tr>
+</table>
+
 #### Comments
 
 Comments embedded within the sorted block are made to stick with their

goldens/skip_lines.in

@@ -34,3 +34,25 @@ This line should not be sorted.
   Charlie | Baz
   <!-- keep-sorted-test end -->
 <!-- keep-sorted-test end -->
+
+Skip lines with group_prefixes:
+// keep-sorted-test start skip_lines=2 group_prefixes=:
+| birds        |
+| ------------ |
+| blue footed  |
+: booby        |
+| crested      |
+: bobwhite     |
+| anhinga      |
+// keep-sorted-test end
+
+Skip lines with group_prefixes indented:
+// keep-sorted-test start skip_lines=2 group_prefixes=:
+    | birds        |
+    | ------------ |
+    | blue footed  |
+    : booby        |
+    | crested      |
+    : bobwhite     |
+    | anhinga      |
+// keep-sorted-test end

goldens/skip_lines.out

@@ -34,3 +34,25 @@ This line should not be sorted.
   Bravo   | Foxtrot
   <!-- keep-sorted-test end -->
 <!-- keep-sorted-test end -->
+
+Skip lines with group_prefixes:
+// keep-sorted-test start skip_lines=2 group_prefixes=:
+| birds        |
+| ------------ |
+| anhinga      |
+| blue footed  |
+: booby        |
+| crested      |
+: bobwhite     |
+// keep-sorted-test end
+
+Skip lines with group_prefixes indented:
+// keep-sorted-test start skip_lines=2 group_prefixes=:
+    | birds        |
+    | ------------ |
+    | anhinga      |
+    | blue footed  |
+    : booby        |
+    | crested      |
+    : bobwhite     |
+// keep-sorted-test end

keepsorted/keep_sorted_test.go

@@ -29,6 +29,7 @@ var (
 		Lint:             true,
 		SkipLines:        0,
 		Group:            true,
+		GroupPrefixes:    nil,
 		IgnorePrefixes:   nil,
 		Numeric:          false,
 		StickyComments:   true,
@@ -1266,6 +1267,33 @@ func TestLineGrouping(t *testing.T) {
 				}},
 			},
 		},
+		{
+			name: "Group_Prefixes",
+			opts: defaultOptionsWith(func(opts *blockOptions) {
+				opts.GroupPrefixes = map[string]bool{"and": true, "with": true}
+				opts.Block = false
+			}),
+
+			want: []lineGroup{
+				{nil, []string{
+					"peanut butter",
+					"and jelly",
+				}},
+				{nil, []string{
+					"spaghetti",
+					"with meatballs",
+				}},
+				{nil, []string{
+					"hamburger",
+					"  with lettuce",
+					" and tomatoes",
+					"and cheese",
+				}},
+				{nil, []string{
+					"dogs and cats",
+				}},
+			},
+		},
 		{
 			name: "Group_UnindentedNewlines",
 			opts: defaultOptionsWith(func(opts *blockOptions) {
@@ -1567,6 +1595,15 @@ func TestBlockOptions(t *testing.T) {
 				opts.IgnorePrefixes = []string{"a", "b", "c", "d"}
 			}),
 		},
+		{
+			name: "GroupPrefixesRequiresGrouping",
+			in:   "// keep-sorted-test group_prefixes=a,b,c group=no",
+
+			want: defaultOptionsWith(func(opts *blockOptions) {
+				opts.Group = false
+			}),
+			wantErr: "group_prefixes may not be used with group=no",
+		},
 		{
 			name: "ignore_prefixes_ChecksLognestPrefixesFirst",
 			in:   "// keep-sorted-test ignore_prefixes=DoSomething(,DoSomething({",

keepsorted/line_group.go

@@ -82,6 +82,8 @@ func groupLines(lines []string, metadata blockMetadata) []lineGroup {
 			appendLine(i, l)
 		} else if metadata.opts.Group && (!lineRange.empty() && initialIndent != nil && indents[i] > *initialIndent || numUnmatchedStartDirectives > 0) {
 			appendLine(i, l)
+		} else if metadata.opts.Group && metadata.opts.hasGroupPrefix(l) {
+			appendLine(i, l)
 		} else if metadata.opts.hasStickyPrefix(l) {
 			if !lineRange.empty() {
 				finishGroup()

keepsorted/options.go

@@ -56,6 +56,8 @@ type blockOptions struct {
 	SkipLines int `key:"skip_lines"`
 	// Group determines whether we group lines together based on increasing indentation.
 	Group bool `default:"true"`
+	// GroupPrefixes tells us about other types of lines that should be added to a group.
+	GroupPrefixes map[string]bool `key:"group_prefixes"`
 	// Block opts us into a more complicated algorithm to try and understand blocks of code.
 	Block bool `default:"false"`
 	// StickyComments tells us to attach comments to the line immediately below them while sorting.
@@ -114,6 +116,11 @@ func (f *Fixer) parseBlockOptions(startLine string) (blockOptions, error) {
 		ret.SkipLines = 0
 	}
 
+	if ret.GroupPrefixes != nil && !ret.Group {
+		errs = errors.Join(errs, fmt.Errorf("group_prefixes may not be used with group=no"))
+		ret.GroupPrefixes = nil
+	}
+
 	if cm := f.guessCommentMarker(startLine); cm != "" {
 		ret.commentMarker = cm
 		if ret.StickyComments {
@@ -216,17 +223,30 @@ func (f *Fixer) guessCommentMarker(startLine string) string {
 	return ""
 }
 
-// hasStickyPrefix determines if s has one of the StickyPrefixes.
-func (opts blockOptions) hasStickyPrefix(s string) bool {
+// hasPrefix determines if s has one of the prefixes.
+func hasPrefix(s string, prefixes map[string]bool) bool {
+	if len(prefixes) == 0 {
+		return false
+	}
 	s = strings.TrimLeftFunc(s, unicode.IsSpace)
-	for p := range opts.StickyPrefixes {
+	for p := range prefixes {
 		if strings.HasPrefix(s, p) {
 			return true
 		}
 	}
 	return false
 }
 
+// hasStickyPrefix determines if s has one of the StickyPrefixes.
+func (opts blockOptions) hasStickyPrefix(s string) bool {
+	return hasPrefix(s, opts.StickyPrefixes)
+}
+
+// hasGroupPrefix determines if s has one of the GroupPrefixes.
+func (opts blockOptions) hasGroupPrefix(s string) bool {
+	return hasPrefix(s, opts.GroupPrefixes)
+}
+
 // removeIgnorePrefix removes the first matching IgnorePrefixes from s, if s
 // matches one of the IgnorePrefixes.
 func (opts blockOptions) removeIgnorePrefix(s string) (string, bool) {