add "plan" command

CHANGES.md

@@ -1,5 +1,9 @@
 # Changelist of gmig releases
 
+## v1.7.0, 2018-09-28
+
+- add "plan" command that logs all commands that would be executed on "up".
+
 ## v1.6.0
 
 - add options to new to set the commands for the do,undo,view section directly

README.md

@@ -68,6 +68,7 @@ and use the `view` subcommand.
         up       Runs the do section of all pending migrations in order, one after the other.
                  If a migration file is specified then stop after applying that one.
         down     Runs the undo section of the last applied migration only.
+        plan     Log commands of the do section of all pending migrations in order, one after the other.
         status   List all migrations with details compared to the current state.
         view     Runs the view section of all applied migrations to see the current state reported by your infrastructure.
         force    state | do | undo
@@ -133,6 +134,11 @@ List all migrations with an indicator (applied,pending) whether is has been appl
 
 Run this command in the directory where all migrations are stored. Use `--migrations` for a different location.
 
+### plan  [path] [|migration file] [--migrations folder]
+
+Log commands of the `do` section of all pending migrations in order, one after the other.
+If `migration file` is given then stop after applying that one.
+
 ### up [path] [|migration file] [--migrations folder]
 
 Executes the `do` section of each pending migration compared to the last applied change to the infrastructure.

commands.go

@@ -22,6 +22,7 @@ const (
 	pending             = "... pending ..."
 	execDo              = "...      do ..."
 	execUndo            = "...    undo ..."
+	execPlan            = "...    plan ..."
 	stopped             = "... stopped ..."
 )
 
@@ -60,6 +61,14 @@ func cmdCreateMigration(c *cli.Context) error {
 }
 
 func cmdMigrationsUp(c *cli.Context) error {
+	return runMigrations(c, !true)
+}
+
+func cmdMigrationsPlan(c *cli.Context) error {
+	return runMigrations(c, true)
+}
+
+func runMigrations(c *cli.Context, isLogOnly bool) error {
 	mtx, err := getMigrationContext(c)
 	if err != nil {
 		printError(err.Error())
@@ -84,26 +93,38 @@ func cmdMigrationsUp(c *cli.Context) error {
 		reportError(mtx.stateProvider.Config(), "up until stop", errors.New("No such migration file: "+stopAfter))
 		return errAbort
 	}
+	prettyWidth := largestWithOf(all)
 	for _, each := range all {
 		log.Println(statusSeparator)
-		log.Println(execDo, pretty(each.Filename))
-		if err := ExecuteAll(each.DoSection, mtx.config().shellEnv(), c.GlobalBool("v")); err != nil {
-			reportError(mtx.stateProvider.Config(), "do", err)
-			return errAbort
+		leadingTitle := execDo
+		if isLogOnly {
+			leadingTitle = execPlan
 		}
-		mtx.lastApplied = each.Filename
-		// save after each succesful migration
-		if err := mtx.stateProvider.SaveState(mtx.lastApplied); err != nil {
-			reportError(mtx.stateProvider.Config(), "save state", err)
-			return errAbort
+		log.Printf("%s %-"+strconv.Itoa(prettyWidth)+"s (%s)\n", leadingTitle, pretty(each.Filename), each.Filename)
+		if isLogOnly {
+			log.Println("")
+			if SimulateAll(each.DoSection, mtx.config().shellEnv(), true); err != nil {
+				reportError(mtx.stateProvider.Config(), "plan do", err)
+				return errAbort
+			}
+		} else {
+			if err := ExecuteAll(each.DoSection, mtx.config().shellEnv(), c.GlobalBool("v")); err != nil {
+				reportError(mtx.stateProvider.Config(), "do", err)
+				return errAbort
+			}
+			mtx.lastApplied = each.Filename
+			// save after each succesful migration
+			if err := mtx.stateProvider.SaveState(mtx.lastApplied); err != nil {
+				reportError(mtx.stateProvider.Config(), "save state", err)
+				return errAbort
+			}
 		}
 		// if not empty then stop after applying this migration
 		if stopAfter == each.Filename {
 			log.Println(stopped)
 			log.Println(statusSeparator)
 			break
 		}
-		log.Println(statusSeparator)
 	}
 	return nil
 }
@@ -139,6 +160,17 @@ func cmdMigrationsDown(c *cli.Context) error {
 	return nil
 }
 
+func largestWithOf(list []Migration) int {
+	prettyWidth := 0
+	for _, each := range list {
+		pf := pretty(each.Filename)
+		if len(pf) > prettyWidth {
+			prettyWidth = len(pf)
+		}
+	}
+	return prettyWidth
+}
+
 func cmdMigrationsStatus(c *cli.Context) error {
 	mtx, err := getMigrationContext(c)
 	if err != nil {
@@ -152,13 +184,7 @@ func cmdMigrationsStatus(c *cli.Context) error {
 	}
 	log.Println(statusSeparator)
 	var last string
-	prettyWidth := 0
-	for _, each := range all {
-		pf := pretty(each.Filename)
-		if len(pf) > prettyWidth {
-			prettyWidth = len(pf)
-		}
-	}
+	prettyWidth := largestWithOf(all)
 	for _, each := range all {
 		status := applied
 		if each.Filename > mtx.lastApplied {

main.go

@@ -79,6 +79,18 @@ func newApp() *cli.App {
 			ArgsUsage: `[title]
 				title - what the effect of this migration is on infrastructure.`,
 		},
+		{
+			Name:  "plan",
+			Usage: "Log commands of the do section of all pending migrations in order, one after the other. If a migration file is specified then stop after applying that one.",
+			Action: func(c *cli.Context) error {
+				defer started(c, "plan = log commands of pending migrations")()
+				return cmdMigrationsPlan(c)
+			},
+			Flags: []cli.Flag{migrationsFlag},
+			ArgsUsage: `[path] [stop] 
+				path - name of the folder that contains the configuration of the target project.
+				stop - (optional) the name of the migration file after which applying migrations will stop.`,
+		},
 		{
 			Name:  "up",
 			Usage: "Runs the do section of all pending migrations in order, one after the other. If a migration file is specified then stop after applying that one.",

migration.go

@@ -91,6 +91,38 @@ func ExecuteAll(commands []string, envs []string, verbose bool) error {
 	return nil
 }
 
+// SimulateAll logs expanded commands using the environment variables of both the config and the OS.
+func SimulateAll(commands []string, envs []string, verbose bool) error {
+	allEnv := append(os.Environ(), envs...)
+	envMap := map[string]string{}
+	for _, each := range allEnv {
+		kv := strings.Split(each, "=")
+		envMap[kv[0]] = kv[1]
+	}
+	for _, each := range commands {
+		log.Println(expandVarsIn(envMap, each))
+	}
+	return nil
+}
+
+// expandVarsIn returns a command with all occurrences of environment variables replaced by known values.
+func expandVarsIn(envs map[string]string, command string) string {
+	// assume no recurse expand
+	expanded := command
+	for k, v := range envs {
+		// if the value itself is a known variable then skip it
+		if strings.HasPrefix(v, "$") {
+			if _, ok := envs[v]; ok {
+				log.Printf("Warning, skipping non-expandable environment var %s=%v\n", k, v)
+				continue
+			}
+		}
+		varName := "$" + k
+		expanded = strings.Replace(expanded, varName, v, -1)
+	}
+	return expanded
+}
+
 func setupShellScript(verbose bool) string {
 	flag := "-v"
 	if verbose {