Merge pull request #42 from gruntwork-io/skip-hooks

Add ability to skip hooks

_docs/README.md

@@ -206,12 +206,14 @@ hooks:
         - <ARG>
       env:
         <KEY>: <VALUE>        
+      skip: <CONDITION>
   after:              
     - command: <CMD>
       args:
         - <ARG>
       env:
         <KEY>: <VALUE>
+      skip: <CONDITION>
 ```
 
 Here's an example:
@@ -399,6 +401,9 @@ Note the following:
           - {{"{{"}} .AnotherVariable {{"}}"}}
     ```
 * Boilerplate runs your `command` with the working directory set to the `--template-folder` option.
+* `skip` (Optional): Skip this hook if this condition, which can use Go templating syntax and 
+  boilerplate variables, evaluates to the string `true`. This is useful to conditionally enable or disable 
+  dependencies.
 * For an alternative way to execute commands, see the `shell` helper in [template helpers](#template-helpers).
 
 #### Templates

config/config_test.go

@@ -593,6 +593,7 @@ const CONFIG_MULTIPLE_HOOKS =
        env:
          foo: bar
          baz: blah
+       skip: "true"
 
      - command: run-some-script.sh
        args:
@@ -601,6 +602,7 @@ const CONFIG_MULTIPLE_HOOKS =
 
    after:
      - command: foo
+       skip: "{{ .baz }}"
      - command: bar
 `
 
@@ -613,11 +615,11 @@ func TestParseBoilerplateConfigMultipleHooks(t *testing.T) {
 		Dependencies: []variables.Dependency{},
 		Hooks: variables.Hooks{
 			BeforeHooks: []variables.Hook{
-				{Command: "echo", Args: []string{"Hello World"}, Env: map[string]string{"foo": "bar", "baz": "blah"}},
+				{Command: "echo", Args: []string{"Hello World"}, Env: map[string]string{"foo": "bar", "baz": "blah"}, Skip: "true"},
 				{Command: "run-some-script.sh", Args: []string{"{{ .foo }}", "{{ .bar }}"}},
 			},
 			AfterHooks: []variables.Hook{
-				{Command: "foo"},
+				{Command: "foo", Skip: "{{ .baz }}"},
 				{Command: "bar"},
 			},
 		},

examples/shell/boilerplate.yml

@@ -14,6 +14,13 @@ hooks:
       env:
         TEXT: "{{ .Text }} - executed via a before hook"
 
+    - command: ./example-script-2.sh
+      args:
+        - "{{ outputFolder }}/before-hook-should-be-skipped.txt"
+      env:
+        TEXT: "this hook should be skipped"
+      skip: "true"
+
   after:
     - command: echo
       args:

templates/template_processor.go

@@ -76,6 +76,15 @@ func processHooks(hooks []variables.Hook, opts *options.BoilerplateOptions, vars
 
 // Process the given hook, which is a script that should be execute at the command-line
 func processHook(hook variables.Hook, opts *options.BoilerplateOptions, vars map[string]interface{}) error {
+	skip, err := shouldSkipHook(hook, opts, vars)
+	if err != nil {
+		return err
+	}
+	if skip {
+		util.Logger.Printf("Skipping hook with command '%s'", hook.Command)
+		return nil
+	}
+
 	cmd, err := render.RenderTemplate(config.BoilerplateConfigPath(opts.TemplateFolder), hook.Command, vars, opts)
 	if err != nil {
 		return err
@@ -108,6 +117,21 @@ func processHook(hook variables.Hook, opts *options.BoilerplateOptions, vars map
 	return util.RunShellCommand(opts.TemplateFolder, envVars, cmd, args...)
 }
 
+// Return true if the "skip" condition of this hook evaluates to true
+func shouldSkipHook(hook variables.Hook, opts *options.BoilerplateOptions, vars map[string]interface{}) (bool, error) {
+	if hook.Skip == "" {
+		return false, nil
+	}
+
+	rendered, err := render.RenderTemplateRecursively(opts.TemplateFolder, hook.Skip, vars, opts)
+	if err != nil {
+		return false, err
+	}
+
+	util.Logger.Printf("Skip attribute for hook with command '%s' evaluated to '%s'", hook.Command, rendered)
+	return rendered == "true", nil
+}
+
 // Execute the boilerplate templates in the given list of dependencies
 func processDependencies(dependencies []variables.Dependency, opts *options.BoilerplateOptions, variables map[string]interface{}) error {
 	for _, dependency := range dependencies {

variables/hooks.go

@@ -5,6 +5,7 @@ type Hook struct {
 	Command string
 	Args    []string
 	Env     map[string]string
+	Skip    string
 }
 
 // All the scripts to execute as boilerplate hooks
@@ -22,13 +23,15 @@ type Hooks struct {
 //         - <ARG>
 //       env:
 //         <KEY>: <VALUE>
+//       skip: <CONDITION>
 //
 //   after:
 //     - command: <CMD>
 //       args:
 //         - <ARG>
 //       env:
 //         <KEY>: <VALUE>
+//       skip: <CONDITION>
 //
 // This method takes the data above and unmarshals it into a Hooks struct
 func UnmarshalHooksFromBoilerplateConfigYaml(fields map[string]interface{}) (Hooks, error) {
@@ -111,5 +114,14 @@ func unmarshalHookFromBoilerplateConfigYaml(fields map[string]interface{}, hookN
 		return nil, err
 	}
 
-	return &Hook{Command: *command, Args: args, Env: env}, nil
+	skipPtr, err := unmarshalStringField(fields, "skip", false, hookName)
+	if err != nil {
+		return nil, err
+	}
+	var skip string
+	if skipPtr != nil {
+		skip = *skipPtr
+	}
+
+	return &Hook{Command: *command, Args: args, Env: env, Skip: skip}, nil
 }