feat: add pipeline priority field

Allows for fine-grained control of execution order.

Signed-off-by: Brian McGee <brian@bmcgee.ie>

config/config_test.go

@@ -59,6 +59,18 @@ func TestReadConfigFile(t *testing.T) {
 	as.Nil(alejandra.Options)
 	as.Equal([]string{"*.nix"}, alejandra.Includes)
 	as.Equal([]string{"examples/nix/sources.nix"}, alejandra.Excludes)
+	as.Equal("nix", alejandra.Pipeline)
+	as.Equal(1, alejandra.Priority)
+
+	// deadnix
+	deadnix, ok := cfg.Formatters["deadnix"]
+	as.True(ok, "deadnix formatter not found")
+	as.Equal("deadnix", deadnix.Command)
+	as.Nil(deadnix.Options)
+	as.Equal([]string{"*.nix"}, deadnix.Includes)
+	as.Nil(deadnix.Excludes)
+	as.Equal("nix", deadnix.Pipeline)
+	as.Equal(2, deadnix.Priority)
 
 	// ruby
 	ruby, ok := cfg.Formatters["ruby"]

config/formatter.go

@@ -9,6 +9,8 @@ type Formatter struct {
 	Includes []string
 	// Excludes is an optional list of glob patterns used to exclude certain files from this Formatter.
 	Excludes []string
-	//
+	// Indicates this formatter should be executed as part of a group of formatters all sharing the same pipeline key.
 	Pipeline string
+	// Indicates the order of precedence when executing as part of a pipeline.
+	Priority int
 }

format/pipeline.go

@@ -1,6 +1,9 @@
 package format
 
-import "context"
+import (
+	"context"
+	"slices"
+)
 
 type Pipeline struct {
 	sequence []*Formatter
@@ -8,6 +11,10 @@ type Pipeline struct {
 
 func (p *Pipeline) Add(f *Formatter) {
 	p.sequence = append(p.sequence, f)
+	// sort by priority in ascending order
+	slices.SortFunc(p.sequence, func(a, b *Formatter) int {
+		return a.config.Priority - b.config.Priority
+	})
 }
 
 func (p *Pipeline) Wants(path string) bool {

test/examples/treefmt.toml

@@ -32,11 +32,13 @@ includes = ["*.nix"]
 # Act as an example on how to exclude specific files
 excludes = ["examples/nix/sources.nix"]
 pipeline = "nix"
+priority = 1
 
 [formatter.deadnix]
 command = "deadnix"
 includes = ["*.nix"]
 pipeline = "nix"
+priority = 2
 
 [formatter.ruby]
 command = "rufo"