Validate zero modules (#324)

* Validate zero modules

Adds two private functions in 'internal/module_config':
- func (cfg ModuleConfig) collectMissing() []string
- func findMissing(reflect.Value, string, string, []string)

These are unexported functions that aid in introspecting a datastructure to see if it has all its expected data.
These functions are implicitly invoked via:
- func LoadModuleConfig(string) (ModuleConfig, error)

If there are errors then the program aborts with appropriate output.

* Set description and author in example zero module

* Remove unused code

* Remove unnecessary newline in error log

go.mod

@@ -10,6 +10,7 @@ require (
 	github.com/google/uuid v1.1.1
 	github.com/hashicorp/go-getter v1.4.2-0.20200106182914-9813cbd4eb02
 	github.com/hashicorp/terraform v0.12.26
+	github.com/iancoleman/strcase v0.1.2
 	github.com/juju/ansiterm v0.0.0-20180109212912-720a0952cc2a // indirect
 	github.com/k0kubun/colorstring v0.0.0-20150214042306-9440f1994b88 // indirect
 	github.com/k0kubun/pp v3.0.1+incompatible

go.sum

@@ -204,6 +204,8 @@ github.com/hashicorp/terraform-config-inspect v0.0.0-20191212124732-c6ae6269b9d7
 github.com/hashicorp/terraform-svchost v0.0.0-20191011084731-65d371908596/go.mod h1:kNDNcF7sN4DocDLBkQYz73HGKwN1ANB1blq4lIYLYvg=
 github.com/hashicorp/vault v0.10.4/go.mod h1:KfSyffbKxoVyspOdlaGVjIuwLobi07qD1bAbosPMpP0=
 github.com/hashicorp/yamux v0.0.0-20180604194846-3520598351bb/go.mod h1:+NfK9FKeTrX5uv1uIXGdwYDTeHna2qgaIlx54MXqjAM=
+github.com/iancoleman/strcase v0.1.2 h1:gnomlvw9tnV3ITTAxzKSgTF+8kFWcU/f+TgttpXGz1U=
+github.com/iancoleman/strcase v0.1.2/go.mod h1:SK73tn/9oHe+/Y0h39VT4UCxmurVJkR5NA7kMEAOgSE=
 github.com/inconshreveable/mousetrap v1.0.0 h1:Z8tu5sraLXCXIcARxBp/8cbvlwVa7Z1NHg9XEKhtSvM=
 github.com/inconshreveable/mousetrap v1.0.0/go.mod h1:PxqpIevigyE2G7u3NXJIT2ANytuPF1OarO4DADm73n8=
 github.com/jhump/protoreflect v1.6.0/go.mod h1:eaTn3RZAmMBcV0fifFvlm6VHNz3wSkYyXYWUh7ymB74=
@@ -227,6 +229,7 @@ github.com/kardianos/osext v0.0.0-20190222173326-2bc1f35cddc0/go.mod h1:1NbS8ALr
 github.com/keybase/go-crypto v0.0.0-20161004153544-93f5b35093ba/go.mod h1:ghbZscTyKdM07+Fw3KSi0hcJm+AlEUWj8QLlPtijN/M=
 github.com/kisielk/errcheck v1.1.0/go.mod h1:EZBBE59ingxPouuu3KfxchcWSUPOHkagtvWXihfKN4Q=
 github.com/kisielk/gotool v1.0.0/go.mod h1:XhKaO+MFFWcvkIS/tQcRk01m1F5IRFswLeQ+oQHNcck=
+github.com/konsorten/go-windows-terminal-sequences v1.0.1 h1:mweAR1A6xJ3oS2pRaGiHgQ4OO8tzTaLawm8vnODuwDk=
 github.com/konsorten/go-windows-terminal-sequences v1.0.1/go.mod h1:T0+1ngSBFLxvqU3pZ+m/2kptfBszLMUkC4ZK/EgS/cQ=
 github.com/kr/logfmt v0.0.0-20140226030751-b84e30acd515/go.mod h1:+0opPa2QZZtGFBFZlji/RkVcI2GknAs/DXo4wKdlNEc=
 github.com/kr/pretty v0.1.0 h1:L/CwN0zerZDmRFUapSPitk6f+Q3+0za1rQkzVuMiMFI=

internal/config/moduleconfig/module_config.go

@@ -1,9 +1,16 @@
 package moduleconfig
 
 import (
+	"fmt"
 	"io/ioutil"
+	"log"
+	"reflect"
+	"strings"
 
 	yaml "gopkg.in/yaml.v2"
+
+	"github.com/commitdev/zero/pkg/util/flog"
+	"github.com/iancoleman/strcase"
 )
 
 type ModuleConfig struct {
@@ -48,16 +55,106 @@ type TemplateConfig struct {
 	OutputDir  string `yaml:"outputDir"`
 }
 
+// A "nice" wrapper around findMissing()
+func (cfg ModuleConfig) collectMissing() []string {
+	var missing []string
+	findMissing(reflect.ValueOf(cfg), "", "", &missing)
+
+	return missing
+}
+
 func LoadModuleConfig(filePath string) (ModuleConfig, error) {
 	config := ModuleConfig{}
+
 	data, err := ioutil.ReadFile(filePath)
 	if err != nil {
 		return config, err
 	}
+
 	err = yaml.Unmarshal(data, &config)
 	if err != nil {
 		return config, err
 	}
 
+	missing := config.collectMissing()
+	if len(missing) > 0 {
+		flog.Errorf("%v is missing information", filePath)
+
+		for _, m := range missing {
+			flog.Errorf("\t %v", m)
+		}
+
+		log.Fatal("")
+	}
+
 	return config, nil
 }
+
+// Recurses through a datastructure to find any missing data.
+// This assumes several things:
+// 1. The structure matches that defined by ModuleConfig and its child datastructures.
+// 2. YAML struct field metadata is sufficient to define whether an attribute is missing or not.
+//    That is, "yaml:foo,omitempty" tells us this is not a required field because we can omit it.
+// 3. Slices and arrays are assumed to be optional.
+//
+// As this function recurses through the datastructure, it builds up a string
+// path representing each node's path within the datastructure.
+// If the value of the current node is equal to the zero value for its datatype
+// and its struct field does *not* have a "omitempty" value, then we assume it
+// is missing and add it to the resultset.
+func findMissing(obj reflect.Value, path, metadata string, missing *[]string) {
+	t := obj.Type()
+	switch t.Kind() {
+	case reflect.String:
+		if obj.String() == "" && !strings.Contains(metadata, "omitempty") {
+			*missing = append(*missing, path)
+		}
+
+	case reflect.Slice, reflect.Array:
+		for i := 0; i < obj.Len(); i++ {
+			prefix := fmt.Sprintf("%v[%v]", path, i)
+			findMissing(obj.Index(i), prefix, metadata, missing)
+		}
+
+	case reflect.Struct:
+		for i := 0; i < t.NumField(); i++ {
+			fieldType := t.Field(i)
+			fieldTags, _ := fieldType.Tag.Lookup("yaml")
+			fieldVal := obj.Field(i)
+
+			tags := strings.Split(fieldTags, ",")
+
+			hasOmitEmpty := false
+			// We have all metadata yaml tags, now let's remove the "omitempty" tag if
+			// it is present.
+			// Then if we have only one tag remaining, this must be the expected yaml
+			// identifer.
+			// Otherwise the name of the yaml identifier should match the struct
+			// attribute name.
+			for i := len(tags) - 1; i >= 0; i-- {
+				tag := tags[i]
+				if tag == "omitempty" {
+					hasOmitEmpty = true
+					tags = append(tags[:i], tags[i+1:]...)
+				}
+			}
+
+			yamlName := strcase.ToLowerCamel(fieldType.Name)
+			if len(tags) == 1 && tags[0] != "" { // For some reason, empty tag lists are giving a count of 1.
+				yamlName = tags[0]
+			}
+
+			prefix := yamlName
+			if path != "" {
+				prefix = fmt.Sprintf("%v.%v", path, yamlName)
+			}
+
+			zeroVal := reflect.Zero(fieldType.Type)
+			if fieldVal == zeroVal && !hasOmitEmpty {
+				*missing = append(*missing, prefix)
+			}
+
+			findMissing(fieldVal, prefix, fieldTags, missing)
+		}
+	}
+}

tests/test_data/modules/ci/zero-module.yml

@@ -1,6 +1,6 @@
 name: "CI templates"
-description: ""
-author: ""
+description: "CI description"
+author: "CI author"
 icon: ""
 thumbnail: ""
 
@@ -10,25 +10,24 @@ requiredCredentials:
   - github
 
 # Template variables to populate, these could be overwritten by the file spefic frontmatter variables
-template: 
-  # strictMode: true # will only parse files that includes the .tmpl.* extension, otherwise it will copy file 
+template:
+  # strictMode: true # will only parse files that includes the .tmpl.* extension, otherwise it will copy file
   delimiters:
     - "<%"
     - "%>"
   inputDir: 'templates'
   outputDir: ".circleci"
 
 # required context parameters: will throw a warning message at the end if any of the context parameters are not present
-# contextRequired: 
+# contextRequired:
 #   - cognitoPoolID
 #   - cognitoClientID
 
 # parameters required from user to populate the template params
-parameters: 
+parameters:
   - field: platform
     label: CI Platform
     # default: github
-    options: 
+    options:
       - github
       - circlci
-