feat(check-plugin): apply fixes flag

Add --fix / -x which automatically applies go.mod fixes instead of
just printing them out.

go.mod

@@ -11,7 +11,7 @@ require (
 	github.com/santhosh-tekuri/jsonschema/v5 v5.0.0
 	github.com/spf13/cobra v1.1.3
 	github.com/stretchr/testify v1.9.0
-	golang.org/x/mod v0.12.0
+	golang.org/x/mod v0.19.0
 )
 
 require (

go.sum

@@ -605,8 +605,8 @@ golang.org/x/mod v0.4.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
 golang.org/x/mod v0.4.1/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
 golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
 golang.org/x/mod v0.8.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
-golang.org/x/mod v0.12.0 h1:rmsUpXtvNzj340zd98LZ4KntptpfRHwpFOHG188oHXc=
-golang.org/x/mod v0.12.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
+golang.org/x/mod v0.19.0 h1:fEdghXQSo20giMthA7cd28ZC+jts4amQ3YMXiP5oMQ8=
+golang.org/x/mod v0.19.0/go.mod h1:hTbmBsO62+eylJbnUtE2MGJUyE7QWk4xUqPFrRgJ+7c=
 golang.org/x/net v0.0.0-20180724234803-3673e40ba225/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20180826012351-8a410e7b638d/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20181023162649-9b4f9f5ad519/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=

plugin.go

@@ -8,20 +8,33 @@ import (
 	"github.com/krakendio/krakend-cobra/v2/plugin"
 	"github.com/spf13/cobra"
 	"golang.org/x/mod/modfile"
+	"golang.org/x/mod/module"
 )
 
-// indirectRequires returns the indirect dependencies of the go.sum file.
-func indirectRequires(goSum string) (map[string]struct{}, error) {
-	dir := filepath.Dir(goSum)
-	filename := filepath.Join(dir, "go.mod")
+const (
+	// goName is the name of the diff which represents the go version.
+	goName = "go"
+
+	// libcName is the name of the diff which represents the libc version.
+	libcName = "libc"
+)
+
+// goMod returns the go.mod file path from the go.sum file path.
+func goMod(goSum string) string {
+	return filepath.Join(filepath.Dir(goSum), "go.mod")
+}
+
+// indirectRequires returns the details and indirect dependencies of the go.sum file.
+func indirectRequires(goSum string) (*modfile.File, map[string]struct{}, error) {
+	filename := goMod(goSum)
 	data, err := os.ReadFile(filename)
 	if err != nil {
-		return nil, fmt.Errorf("reading go.mod: %w", err)
+		return nil, nil, fmt.Errorf("read go.mod: %w", err)
 	}
 
 	f, err := modfile.Parse(filename, data, nil)
 	if err != nil {
-		return nil, fmt.Errorf("parsing go.mod: %w", err)
+		return nil, nil, fmt.Errorf("parse go.mod: %w", err)
 	}
 
 	indirects := map[string]struct{}{}
@@ -31,7 +44,23 @@ func indirectRequires(goSum string) (map[string]struct{}, error) {
 		}
 	}
 
-	return indirects, nil
+	return f, indirects, nil
+}
+
+// writeModFile writes the modfile.File to the go.mod file determined from goSum.
+func writeModFile(goSum string, f *modfile.File) error {
+	f.Cleanup()
+	data, err := f.Format()
+	if err != nil {
+		return fmt.Errorf("format go.mod: %w", err)
+	}
+
+	filename := goMod(goSum)
+	if err = os.WriteFile(filename, data, 0644); err != nil {
+		return fmt.Errorf("write go.sum: %w", err)
+	}
+
+	return nil
 }
 
 // getBuildInfo returns the dependencies of the binary calling it.
@@ -66,32 +95,99 @@ func pluginFuncErr(cmd *cobra.Command, _ []string) error {
 		return nil
 	}
 
-	if gogetEnabled {
-		indirects, err := indirectRequires(goSum)
-		if err != nil {
+	var indirects map[string]struct{}
+	var modFile *modfile.File
+	if gogetEnabled || fixEnabled {
+		if modFile, indirects, err = indirectRequires(goSum); err != nil {
 			return err
 		}
-		for _, diff := range diffs {
-			if diff.Name != "go" && diff.Name != "libc" {
-				if _, ok := indirects[diff.Name]; ok {
-					cmd.Printf("go mod edit --replace %s=%s@%s\n", diff.Name, diff.Name, diff.Expected)
-				} else {
-					cmd.Printf("go get %s@%s\n", diff.Name, diff.Expected)
-				}
+	}
+
+	var fixed int
+	if !fixEnabled {
+		outputFixes(cmd, diffs, indirects)
+	} else if fixed, err = applyFixes(cmd, diffs, modFile, indirects); err != nil {
+		return err
+	}
+
+	// Report any remaining incompatibilities.
+	if len(diffs) != fixed {
+		if fixed > 0 {
+			return fmt.Errorf("%d incompatibilities fixed, %d left", fixed, len(diffs)-fixed)
+		}
+
+		return fmt.Errorf("%d incompatibilities found", len(diffs))
+	}
+
+	return nil
+}
+
+// outputFixes prints the incompatibilities.
+func outputFixes(cmd *cobra.Command, diffs []plugin.Diff, indirects map[string]struct{}) {
+	for _, diff := range diffs {
+		if diff.Name != goName && diff.Name != libcName && gogetEnabled {
+			if _, ok := indirects[diff.Name]; ok {
+				cmd.Printf("go mod edit --replace %s=%s@%s\n", diff.Name, diff.Name, diff.Expected)
+			} else {
+				cmd.Printf("go get %s@%s\n", diff.Name, diff.Expected)
+			}
+			continue
+		}
+
+		cmd.Println(diff.Name)
+		cmd.Println("\thave:", diff.Have)
+		cmd.Println("\twant:", diff.Expected)
+	}
+}
+
+// applyFixes applies the fixes and returns the number of incompatibilities fixed.
+func applyFixes(cmd *cobra.Command, diffs []plugin.Diff, modFile *modfile.File, indirects map[string]struct{}) (int, error) {
+	var replaces []plugin.Diff
+	var requires []*modfile.Require
+	for _, diff := range diffs {
+		if diff.Name != goName && diff.Name != libcName {
+			if _, ok := indirects[diff.Name]; ok {
+				replaces = append(replaces, diff)
 				continue
 			}
 
-			cmd.Println(diff.Name)
-			cmd.Println("\thave:", diff.Have)
-			cmd.Println("\twant:", diff.Expected)
+			requires = append(requires, &modfile.Require{
+				Mod: module.Version{
+					Path:    diff.Name,
+					Version: diff.Expected,
+				},
+			})
+			continue
 		}
-	} else {
-		for _, diff := range diffs {
-			cmd.Println(diff.Name)
-			cmd.Println("\thave:", diff.Have)
-			cmd.Println("\twant:", diff.Expected)
+
+		cmd.Println(diff.Name)
+		cmd.Println("\thave:", diff.Have)
+		cmd.Println("\twant:", diff.Expected)
+	}
+
+	if len(requires) > 0 {
+		// We use the modfile.SetRequireSeparateIndirect to avoid adding direct
+		// dependencies to the direct block as per:
+		// https://github.com/golang/go/issues/69050
+		modFile.SetRequireSeparateIndirect(append(modFile.Require, requires...))
+	}
+
+	// Add replaces after requires.
+	for _, diff := range replaces {
+		if err := modFile.AddReplace(diff.Name, "", diff.Name, diff.Expected); err != nil {
+			return 0, fmt.Errorf("add replace: %w", err)
 		}
 	}
 
-	return fmt.Errorf("%d incompatibilities found", len(diffs))
+	fixed := len(replaces) + len(requires)
+	if fixed > 0 {
+		modFile.Cleanup()
+		if err := writeModFile(goSum, modFile); err != nil {
+			return 0, err
+		}
+
+		cmd.Printf("%d incompatibilities fixed\n", fixed)
+	}
+
+	return fixed, nil
 }