cmd/cue: add mod edit command

This command allows some automatic editing of the module.cue file.
The design is patterned after the `go mod edit` command.

For #3017.

Signed-off-by: Roger Peppe <rogpeppe@gmail.com>
Change-Id: Ia46be7fa6cdfd84aff131f2196e052268cdc3b03
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1193116
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>

cmd/cue/cmd/mod.go

@@ -52,6 +52,7 @@ See also:
 		}),
 	}
 
+	cmd.AddCommand(newModEditCmd(c))
 	cmd.AddCommand(newModGetCmd(c))
 	cmd.AddCommand(newModInitCmd(c))
 	cmd.AddCommand(newModRegistryCmd(c))

cmd/cue/cmd/modedit.go

@@ -0,0 +1,210 @@
+// Copyright 2024 The CUE Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package cmd
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strconv"
+
+	"cuelang.org/go/mod/modfile"
+	"cuelang.org/go/mod/module"
+	"github.com/spf13/cobra"
+	"github.com/spf13/pflag"
+)
+
+func newModEditCmd(c *Command) *cobra.Command {
+	editCmd := &modEditCmd{}
+	cmd := &cobra.Command{
+		Use:   "edit",
+		Short: "edit cue.mod/module.cue",
+		Long: `WARNING: THIS COMMAND IS EXPERIMENTAL.
+
+Edit provides a command-line interface for editing cue.mod/module.cue.
+It reads only that file; it does not look up information about the modules
+involved.
+
+The editing flags specify a sequence of editing operations.
+
+The -require=path@version and -drop-require=path@majorversion flags add
+and drop a requirement on the given module path and version. Note that
+-require overrides any existing requirements on path. These flags are
+mainly for tools that understand the module graph. Users should prefer
+'cue get path@version' which makes other go.mod adjustments as needed
+to satisfy constraints imposed by other modules.
+
+The --module flag changes the module's path (the module.cue file's module field).
+The --source flag changes the module's declared source.
+The --drop-source flag removes the source field.
+
+Note: you must enable the modules experiment with:
+	export CUE_EXPERIMENT=modules
+for this command to work.
+`,
+		RunE: mkRunE(c, editCmd.run),
+		Args: cobra.ExactArgs(0),
+	}
+	addFlagVar(cmd, flagFunc(editCmd.flagSource), "source", "set the source field")
+	addFlagVar(cmd, boolFlagFunc(editCmd.flagDropSource), "drop-source", "remove the source field")
+	addFlagVar(cmd, flagFunc(editCmd.flagModule), "module", "set the module path")
+	addFlagVar(cmd, flagFunc(editCmd.flagRequire), "require", "add a required module@version")
+	addFlagVar(cmd, flagFunc(editCmd.flagDropRequire), "drop-require", "remove a requirement")
+
+	return cmd
+}
+
+type modEditCmd struct {
+	edits []func(*modfile.File) error
+}
+
+func (c *modEditCmd) run(cmd *Command, args []string) error {
+	modRoot, err := findModuleRoot()
+	if err != nil {
+		return err
+	}
+	modPath := filepath.Join(modRoot, "cue.mod", "module.cue")
+	data, err := os.ReadFile(modPath)
+	if err != nil {
+		return err
+	}
+	mf, err := modfile.Parse(data, modPath)
+	if err != nil {
+		return err
+	}
+	for _, edit := range c.edits {
+		if err := edit(mf); err != nil {
+			return err
+		}
+	}
+	newData, err := mf.Format()
+	if err != nil {
+		return fmt.Errorf("internal error: invalid module.cue file generated: %v", err)
+	}
+	if bytes.Equal(newData, data) {
+		return nil
+	}
+	if err := os.WriteFile(modPath, newData, 0o666); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (c *modEditCmd) addEdit(f func(*modfile.File) error) {
+	c.edits = append(c.edits, f)
+}
+
+func (c *modEditCmd) flagSource(arg string) error {
+	if arg != "git" && arg != "none" {
+		return fmt.Errorf("unrecognized source kind %q", arg)
+	}
+	c.addEdit(func(f *modfile.File) error {
+		if f.Source == nil {
+			f.Source = &modfile.Source{}
+		}
+		f.Source.Kind = arg
+		return nil
+	})
+	return nil
+}
+
+func (c *modEditCmd) flagDropSource(arg bool) error {
+	if !arg {
+		return fmt.Errorf("cannot set --drop-source to false")
+	}
+	c.addEdit(func(f *modfile.File) error {
+		f.Source = nil
+		return nil
+	})
+	return nil
+}
+
+func (c *modEditCmd) flagModule(arg string) error {
+	if err := module.CheckPath(arg); err != nil {
+		return err
+	}
+	c.addEdit(func(f *modfile.File) error {
+		f.Module = arg
+		return nil
+	})
+	return nil
+}
+
+func (c *modEditCmd) flagRequire(arg string) error {
+	v, err := module.ParseVersion(arg)
+	if err != nil {
+		return err
+	}
+	c.addEdit(func(f *modfile.File) error {
+		if f.Deps == nil {
+			f.Deps = make(map[string]*modfile.Dep)
+		}
+		vm := v.Path()
+		dep := f.Deps[vm]
+		if dep == nil {
+			dep = &modfile.Dep{}
+			f.Deps[vm] = dep
+		}
+		dep.Version = v.Version()
+		return nil
+	})
+	return nil
+}
+
+func (c *modEditCmd) flagDropRequire(arg string) error {
+	if err := module.CheckPath(arg); err != nil {
+		return err
+	}
+	// TODO allow dropping a requirement without specifying
+	// the major version - we can use the default field to disambiguate.
+	c.addEdit(func(f *modfile.File) error {
+		delete(f.Deps, arg)
+		return nil
+	})
+	return nil
+}
+
+func addFlagVar(cmd *cobra.Command, v pflag.Value, name string, usage string) {
+	flags := cmd.Flags()
+	flags.Var(v, name, usage)
+	// This works around https://github.com/spf13/pflag/issues/281
+	if v, ok := v.(interface{ IsBoolFlag() bool }); ok && v.IsBoolFlag() {
+		flags.Lookup(name).NoOptDefVal = "true"
+	}
+}
+
+type flagFunc func(string) error
+
+func (f flagFunc) String() string     { return "" }
+func (f flagFunc) Set(s string) error { return f(s) }
+func (f flagFunc) Type() string {
+	return "string"
+}
+
+type boolFlagFunc func(bool) error
+
+func (f boolFlagFunc) String() string { return "" }
+func (f boolFlagFunc) Set(s string) error {
+	b, err := strconv.ParseBool(s)
+	if err != nil {
+		return err
+	}
+	return f(b)
+}
+func (f boolFlagFunc) Type() string {
+	return "bool"
+}
+func (f boolFlagFunc) IsBoolFlag() bool { return true }

cmd/cue/cmd/testdata/script/modedit_initial.txtar

@@ -0,0 +1,41 @@
+exec cue mod edit --source git
+cmp cue.mod/module.cue want-module-1
+
+exec cue mod edit --drop-source
+cmp cue.mod/module.cue want-module-2
+
+exec cue mod edit --require foo.bar@v0.2.3
+cmp cue.mod/module.cue want-module-3
+
+! exec cue mod edit --require bad-module!
+cmp stderr want-stderr
+
+exec cue mod edit --drop-require foo.bar@v0
+cmp cue.mod/module.cue want-module-4
+
+exec cue mod edit --module othermain.org@v1
+cmp cue.mod/module.cue want-module-5
+
+
+-- cue.mod/module.cue --
+module: "main.org@v0"
+-- want-module-1 --
+module: "main.org@v0"
+source: {
+	kind: "git"
+}
+-- want-module-2 --
+module: "main.org@v0"
+-- want-module-3 --
+module: "main.org@v0"
+deps: {
+	"foo.bar@v0": {
+		v: "v0.2.3"
+	}
+}
+-- want-stderr --
+invalid argument "bad-module!" for "--require" flag: invalid module path@version "bad-module!"
+-- want-module-4 --
+module: "main.org@v0"
+-- want-module-5 --
+module: "othermain.org@v1"