add "remove" command

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 #### New
 
+- New command `detach` to detach resources from the Terraform state. See the README for details.
 - The script generated by `terravalet import` now prints each command before executing it. This helps to understand which command is being executed.
 
 ### Changes

README.md

@@ -5,6 +5,7 @@ A tool to help with advanced, low-level [Terraform](https://www.terraform.io/) o
 - Rename resources within the same Terraform state, with optional fuzzy match.
 - Move resources from one Terraform state to another.
 - Import existing resources into Terraform state.
+- Detach existing resources from Terraform state.
 
 **DISCLAIMER Manipulating Terraform state is inherently dangerous. It is your responsibility to be careful and ensure you UNDERSTAND what you are doing**.
 
@@ -57,11 +58,12 @@ After the creation of Terravalet, Terraform introduced the `moved` block, which
 
 ## Usage
 
-There are three modes of operation:
+Terravalet supports multiple operations:
 
 - [Rename resources](#rename-resources-within-the-same-state) within the same Terraform state, with optional fuzzy match.
 - [Move resources](#-move-resources-from-one-state-to-another) from one Terraform state to another.
 - [Import existing resources](#-import-existing-resources) into Terraform state.
+- [Detach existing resources]() from Terraform state.
 
 They will be explained in the following sections.
 
@@ -399,6 +401,26 @@ NON ignorable errors:
 
 1. Provider specific argument ID is wrong.
 
+# Detach existing resources
+
+The reason of existence of this command is in the same spirit of `terravalet import`: it is true that `terraform state rm` allows to remove _individual_ resources, but when a real-world resource is composed of multiple terraform resources, using `terraform state rm` becomes tedious and error-prone.
+
+Thus, `terravalet detach` creates all the `state rm` commands for you.
+
+1. Generate the state file in JSON format:
+   ```
+   $ terraform -chdir=<the tf root> show -no-color -json > pre-detach.json
+   ```
+2. Run terravalet detach. As usual, this is a safe operation, since it will only generate a script file:
+   ```
+   $ terravalet detach --up=detach_up.sh --state=pre-detach.json --resource=NAME
+   ```
+3. Validate the generated script file `detach_up.sh`!
+4. Execute:
+   ```
+   $ sh ./detach_up.sh
+   ```
+
 # Making a release
 
 ## Setup

cmddetach.go

@@ -0,0 +1,99 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+)
+
+func doDetach(statePath string, upPath string, resource string) error {
+	stateFile, err := os.Open(statePath)
+	if err != nil {
+		return fmt.Errorf("detach: opening the state file: %s", err)
+	}
+	defer stateFile.Close()
+
+	upFile, err := os.Create(upPath)
+	if err != nil {
+		return fmt.Errorf("detach: creating the up file: %s", err)
+	}
+	defer upFile.Close()
+
+	addresses, err := matchResources(stateFile, resource)
+	if err != nil {
+		return fmt.Errorf("detach: finding matches: %s", err)
+	}
+
+	var bld strings.Builder
+	generateDetachScript(&bld, addresses)
+	_, err = upFile.WriteString(bld.String())
+	if err != nil {
+		return fmt.Errorf("detach: writing script file: %s", err)
+	}
+
+	return nil
+}
+
+// TerraformState is a subset of the fields in the output of
+// terraform show -no-color -json
+type TerraformState struct {
+	FormatVersion    string `json:"format_version"`
+	TerraformVersion string `json:"terraform_version"`
+	Values           struct {
+		RootModule struct {
+			ChildModules []struct {
+				Resources []struct {
+					Address string `json:"address"`
+					Index   string `json:"index"`
+				} `json:"resources"`
+			} `json:"child_modules"`
+		} `json:"root_module"`
+	} `json:"values"`
+}
+
+func matchResources(rd io.Reader, resource string) ([]string, error) {
+	dec := json.NewDecoder(rd)
+	var state TerraformState
+	if err := dec.Decode(&state); err != nil {
+		return nil, err
+	}
+
+	var addresses []string
+	for _, child := range state.Values.RootModule.ChildModules {
+		for _, res := range child.Resources {
+			if matchResource(res.Index, resource) {
+				addresses = append(addresses, res.Address)
+			}
+		}
+	}
+	return addresses, nil
+}
+
+func matchResource(index, resource string) bool {
+	if index == resource {
+		return true
+	}
+	after, found := strings.CutPrefix(index, resource)
+	if !found {
+		return false
+	}
+	if strings.IndexAny(after, ".:") == 0 {
+		return true
+	}
+	return false
+}
+
+func generateDetachScript(wr io.Writer, addresses []string) {
+	fmt.Fprintf(wr, `#! /bin/sh
+# DO NOT EDIT. Generated by https://github.com/pix4D/terravalet
+#
+# This script will detach %d items.
+
+set -e
+`, len(addresses))
+	for _, addr := range addresses {
+		fmt.Fprintf(wr, "\nterraform state rm '%s'\n", addr)
+	}
+}

cmddetach_test.go

@@ -0,0 +1,128 @@
+package main
+
+import (
+	"os"
+	"strings"
+	"testing"
+
+	"github.com/go-quicktest/qt"
+)
+
+func TestMatchResourceSuccess(t *testing.T) {
+	type testCase struct {
+		name     string
+		index    string
+		resource string
+	}
+
+	test := func(t *testing.T, tc testCase) {
+		qt.Assert(t, qt.IsTrue(matchResource(tc.index, tc.resource)))
+	}
+
+	testCases := []testCase{
+		{
+			name:     "exact match",
+			index:    "foo",
+			resource: "foo",
+		},
+		{
+			name:     "dot after match",
+			index:    "foo.AN-",
+			resource: "foo",
+		},
+		{
+			// FIXME this currently passes. Maybe we should err on the side of
+			// caution and change the signature to return an error instead, since
+			// we are not expecting this case???
+			name:     "FIXME multiple dots after match",
+			index:    "foo.banana.AN-",
+			resource: "foo",
+		},
+		{
+			name:     "colon after match",
+			index:    "foo:master",
+			resource: "foo",
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) { test(t, tc) })
+	}
+}
+
+func TestMatchResourceFailure(t *testing.T) {
+	type testCase struct {
+		name     string
+		index    string
+		resource string
+	}
+
+	test := func(t *testing.T, tc testCase) {
+		qt.Assert(t, qt.IsFalse(matchResource(tc.index, tc.resource)),
+			qt.Commentf("index=%s resource=%s", tc.index, tc.resource))
+	}
+
+	testCases := []testCase{
+		{
+			name:     "plain no match",
+			index:    "foo",
+			resource: "bar",
+		},
+		{
+			name:     "prefix match is not enough",
+			index:    "foobar",
+			resource: "foo",
+		},
+		{
+			name:     "wrong separator after prefix",
+			index:    "foo_master",
+			resource: "foo",
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) { test(t, tc) })
+	}
+}
+
+func TestMatchResources(t *testing.T) {
+	fi, err := os.Open("testdata/detach/01_pre_detach.json")
+	qt.Assert(t, qt.IsNil(err))
+	defer fi.Close()
+
+	want := []string{
+		`module.a.b.c["foo"]`,
+		`module.a.b.d["foo.AN-"]`,
+		`module.a.b.e["foo:master*"]`,
+		`module.x.y.z["foo"]`,
+		`module.x.y.k["foo.AN-"]`,
+		`module.x.y.z.j["foo:master*"]`,
+	}
+
+	have, err := matchResources(fi, "foo")
+
+	qt.Assert(t, qt.IsNil(err))
+	qt.Assert(t, qt.DeepEquals(have, want))
+}
+
+func TestGenerateDetachScript(t *testing.T) {
+	addresses := []string{
+		`module.a.b.c["foo"]`,
+		`module.a.b.d["foo.AN-"]`,
+	}
+	var bld strings.Builder
+	want := `#! /bin/sh
+# DO NOT EDIT. Generated by https://github.com/pix4D/terravalet
+#
+# This script will detach 2 items.
+
+set -e
+
+terraform state rm 'module.a.b.c["foo"]'
+
+terraform state rm 'module.a.b.d["foo.AN-"]'
+`
+
+	generateDetachScript(&bld, addresses)
+	qt.Assert(t, qt.Equals(bld.String(), want))
+}

go.mod

@@ -5,8 +5,14 @@ go 1.21
 require (
 	github.com/alexflint/go-arg v1.4.3
 	github.com/dexyk/stringosim v0.0.0-20170922105913-9d0b3e91a842
+	github.com/go-quicktest/qt v1.101.0
 	github.com/google/go-cmp v0.6.0
 	github.com/scylladb/go-set v1.0.3-0.20200225121959-cc7b2070d91e
 )
 
-require github.com/alexflint/go-scalar v1.2.0 // indirect
+require (
+	github.com/alexflint/go-scalar v1.2.0 // indirect
+	github.com/kr/pretty v0.3.1 // indirect
+	github.com/kr/text v0.2.0 // indirect
+	github.com/rogpeppe/go-internal v1.11.0 // indirect
+)

go.sum

@@ -1,32 +1,36 @@
-github.com/alexflint/go-arg v1.4.2 h1:lDWZAXxpAnZUq4qwb86p/3rIJJ2Li81EoMbTMujhVa0=
-github.com/alexflint/go-arg v1.4.2/go.mod h1:9iRbDxne7LcR/GSvEr7ma++GLpdIU1zrghf2y2768kM=
 github.com/alexflint/go-arg v1.4.3 h1:9rwwEBpMXfKQKceuZfYcwuc/7YY7tWJbFsgG5cAU/uo=
 github.com/alexflint/go-arg v1.4.3/go.mod h1:3PZ/wp/8HuqRZMUUgu7I+e1qcpUbvmS258mRXkFH4IA=
-github.com/alexflint/go-scalar v1.0.0/go.mod h1:GpHzbCOZXEKMEcygYQ5n/aa4Aq84zbxjy3MxYW0gjYw=
-github.com/alexflint/go-scalar v1.1.0 h1:aaAouLLzI9TChcPXotr6gUhq+Scr8rl0P9P4PnltbhM=
 github.com/alexflint/go-scalar v1.1.0/go.mod h1:LoFvNMqS1CPrMVltza4LvnGKhaSpc3oyLEBUZVhhS2o=
 github.com/alexflint/go-scalar v1.2.0 h1:WR7JPKkeNpnYIOfHRa7ivM21aWAdHD0gEWHCx+WQBRw=
 github.com/alexflint/go-scalar v1.2.0/go.mod h1:LoFvNMqS1CPrMVltza4LvnGKhaSpc3oyLEBUZVhhS2o=
+github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/dexyk/stringosim v0.0.0-20170922105913-9d0b3e91a842 h1:FWXGhOthNyZKdK0YVyDrkg5dCXOfKvexcRG37U1v6AQ=
 github.com/dexyk/stringosim v0.0.0-20170922105913-9d0b3e91a842/go.mod h1:PfVoEMbmPGFArz22/wIefW9CzuQhdnE+C9ikEzJvb9Q=
 github.com/fatih/set v0.2.1 h1:nn2CaJyknWE/6txyUDGwysr3G5QC6xWB/PtVjPBbeaA=
 github.com/fatih/set v0.2.1/go.mod h1:+RKtMCH+favT2+3YecHGxcc0b4KyVWA1QWWJUs4E0CI=
-github.com/google/go-cmp v0.5.7 h1:81/ik6ipDQS2aGcBfIN5dHDB36BwrStyeAQquSYCV4o=
-github.com/google/go-cmp v0.5.7/go.mod h1:n+brtR0CgQNWTVd5ZUFpTBC8YFBDLK/h/bpaJ8/DtOE=
+github.com/go-quicktest/qt v1.101.0 h1:O1K29Txy5P2OK0dGo59b7b0LR6wKfIhttaAhHUyn7eI=
+github.com/go-quicktest/qt v1.101.0/go.mod h1:14Bz/f7NwaXPtdYEgzsx46kqSxVwTbzVZsDC26tQJow=
 github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
 github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
+github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
+github.com/kr/pretty v0.3.1/go.mod h1:hoEshYVHaxMs3cyo3Yncou5ZscifuDolrwPKZanG3xk=
+github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
+github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
+github.com/pkg/diff v0.0.0-20210226163009-20ebb0f2a09e/go.mod h1:pJLUxLENpZxwdsKMEsNbx1VGcRFpLqf3715MtcvvzbA=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/rogpeppe/go-internal v1.9.0/go.mod h1:WtVeX8xhTBvf0smdhujwtBcq4Qrzq/fJaraNFVN+nFs=
+github.com/rogpeppe/go-internal v1.11.0 h1:cWPaGQEPrBb5/AsnsZesgZZ9yb1OQ+GOISoDNXVBh4M=
+github.com/rogpeppe/go-internal v1.11.0/go.mod h1:ddIwULY96R17DhadqLgMfk9H9tvdUzkipdSkR5nkCZA=
 github.com/scylladb/go-set v1.0.3-0.20200225121959-cc7b2070d91e h1:7q6NSFZDeGfvvtIRwBrU/aegEYJYmvev0cHAwo17zZQ=
 github.com/scylladb/go-set v1.0.3-0.20200225121959-cc7b2070d91e/go.mod h1:DkpGd78rljTxKAnTDPFqXSGxvETQnJyuSOQwsHycqfs=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/testify v1.2.2 h1:bSDNvY7ZPG5RlJ8otE/7V6gMiyenm9RtJ7IUVIAoJ1w=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
+github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
-golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

main.go

@@ -27,6 +27,7 @@ type args struct {
 	MoveAfter  *MoveAfterCmd  `arg:"subcommand:move-after" help:"move resources from one root environment to AFTER another"`
 	MoveBefore *MoveBeforeCmd `arg:"subcommand:move-before" help:"move resources from one root environment to BEFORE another"`
 	Import     *ImportCmd     `arg:"subcommand:import" help:"import resources generated out-of-band of Terraform"`
+	Detach     *DetachCmd     `arg:"subcommand:detach" help:"detach resources from Terraform state"`
 	Version    *struct{}      `arg:"subcommand:version" help:"show version"`
 }
 
@@ -64,6 +65,12 @@ type ImportCmd struct {
 	SrcPlanPath  string `arg:"--src-plan,required" help:"path to the SRC terraform plan in JSON format"`
 }
 
+type DetachCmd struct {
+	Up       string `arg:"required" help:"path of the up script to generate (NNN_TITLE.up.sh)"`
+	State    string `arg:"required" help:"path to to the output of 'terraform show -no-color -json'""`
+	Resource string `arg:"--resource,required" help:"name of the high-level resource to detach (will match multiple terraform resources)"`
+}
+
 func run() error {
 	var args args
 
@@ -86,6 +93,9 @@ func run() error {
 	case args.Import != nil:
 		cmd := args.Import
 		return doImport(cmd.Up, cmd.Down, cmd.SrcPlanPath, cmd.ResourceDefs)
+	case args.Detach != nil:
+		cmd := args.Detach
+		return doDetach(cmd.State, cmd.Up, cmd.Resource)
 	case args.Version != nil:
 		fmt.Println("terravalet", fullVersion)
 		return nil