Add rule generator (#83)

Author: wata727

README.md

@@ -39,3 +39,13 @@ You can easily install the built plugin with the following:
 ```
 $ make install
 ```
+
+## Add a new rule
+
+If you are interested in adding a new rule to this ruleset, you can use the generator. Run the following command:
+
+```
+$ go run ./rules/generator
+```
+
+Follow the instructions to edit the generated files and open a new pull request.

docs/rules/rule.md.tmpl

@@ -0,0 +1,26 @@
+# {{ .RuleName }}
+
+// TODO: Write the rule's description here
+
+## Example
+
+```hcl
+resource "null_resource" "foo" {
+  // TODO: Write the example Terraform code which violates the rule
+}
+```
+
+```
+$ tflint
+
+// TODO: Write the output when inspects the above code
+
+```
+
+## Why
+
+// TODO: Write why you should follow the rule. This section is also a place to explain the value of the rule
+
+## How To Fix
+
+// TODO: Write how to fix it to avoid the problem

go.mod

@@ -3,9 +3,13 @@ module github.com/terraform-linters/tflint-ruleset-google
 go 1.16
 
 require (
+	github.com/dave/dst v0.26.2
 	github.com/google/go-cmp v0.5.4
 	github.com/hashicorp/hcl/v2 v2.9.0
 	github.com/hashicorp/terraform-plugin-sdk/v2 v2.4.4
+	github.com/onsi/ginkgo v1.15.2 // indirect
+	github.com/onsi/gomega v1.11.0 // indirect
+	github.com/serenize/snaker v0.0.0-20201027110005-a7ad2135616e
 	github.com/terraform-linters/tflint-plugin-sdk v0.8.1
 	google.golang.org/api v0.40.0
 )

go.sum

@@ -0,0 +1,101 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"go/format"
+	"io/ioutil"
+	"os"
+	"strings"
+	"text/template"
+
+	"github.com/dave/dst"
+	"github.com/dave/dst/decorator"
+	"github.com/serenize/snaker"
+)
+
+type metadata struct {
+	RuleName   string
+	RuleNameCC string
+}
+
+func main() {
+	buf := bufio.NewReader(os.Stdin)
+	fmt.Print("Rule name? (e.g. google_compute_instance_invalid_machine_type): ")
+	ruleName, err := buf.ReadString('\n')
+	if err != nil {
+		panic(err)
+	}
+	ruleName = strings.Trim(ruleName, "\n")
+
+	meta := &metadata{RuleNameCC: snaker.SnakeToCamel(ruleName), RuleName: ruleName}
+
+	GenerateFileWithLogs(fmt.Sprintf("rules/%s.go", ruleName), "rules/rule.go.tmpl", meta)
+	GenerateFileWithLogs(fmt.Sprintf("rules/%s_test.go", ruleName), "rules/rule_test.go.tmpl", meta)
+	GenerateFileWithLogs(fmt.Sprintf("docs/rules/%s.md", ruleName), "docs/rules/rule.md.tmpl", meta)
+
+	src, err := ioutil.ReadFile("rules/provider.go")
+	if err != nil {
+		panic(err)
+	}
+	dstf, err := decorator.Parse(src)
+	if err != nil {
+		panic(err)
+	}
+
+	dst.Inspect(dstf, func(n dst.Node) bool {
+		switch node := n.(type) {
+		case *dst.CompositeLit:
+			expr := &dst.CallExpr{
+				Fun: &dst.Ident{
+					Name: fmt.Sprintf("New%sRule", meta.RuleNameCC),
+				},
+			}
+			expr.Decs.Before = dst.NewLine
+			expr.Decs.After = dst.NewLine
+			node.Elts = append(node.Elts, expr)
+		}
+		return true
+	})
+
+	fset, astf, err := decorator.RestoreFile(dstf)
+	if err != nil {
+		panic(err)
+	}
+
+	fp, err := os.OpenFile("rules/provider.go", os.O_RDWR, 0755)
+	if err != nil {
+		panic(err)
+	}
+	if err := format.Node(fp, fset, astf); err != nil {
+		panic(err)
+	}
+	fmt.Println("Modified: rules/provider.go")
+
+	fmt.Println(`
+TODO:
+1. Remove all "TODO" comments from generated files.
+2. Write implementation of the rule.
+3. Add a link to the generated documentation into docs/rules/README.md`)
+}
+
+// GenerateFile generates a new file from the passed template and metadata
+func GenerateFile(fileName string, tmplName string, meta interface{}) {
+	file, err := os.Create(fileName)
+	if err != nil {
+		panic(err)
+	}
+
+	tmpl := template.Must(template.ParseFiles(tmplName))
+	err = tmpl.Execute(file, meta)
+	if err != nil {
+		panic(err)
+	}
+}
+
+// GenerateFileWithLogs generates a new file from the passed template and metadata
+// The difference from GenerateFile function is to output logs
+func GenerateFileWithLogs(fileName string, tmplName string, meta interface{}) {
+	GenerateFile(fileName, tmplName, meta)
+	fmt.Printf("Created: %s\n", fileName)
+}

rules/generator/main.go

@@ -0,0 +1,69 @@
+package rules
+
+import (
+	hcl "github.com/hashicorp/hcl/v2"
+	"github.com/terraform-linters/tflint-plugin-sdk/tflint"
+	"github.com/terraform-linters/tflint-ruleset-google/project"
+)
+
+// TODO: Write the rule's description here
+// {{ .RuleNameCC }}Rule checks ...
+type {{ .RuleNameCC }}Rule struct {
+	resourceType  string
+	attributeName string
+}
+
+// New{{ .RuleNameCC }}Rule returns new rule with default attributes
+func New{{ .RuleNameCC }}Rule() *{{ .RuleNameCC }}Rule {
+	return &{{ .RuleNameCC }}Rule{
+		// TODO: Write resource type and attribute name here
+		resourceType:  "...",
+		attributeName: "...",
+	}
+}
+
+// Name returns the rule name
+func (r *{{ .RuleNameCC }}Rule) Name() string {
+	return "{{ .RuleName }}"
+}
+
+// Enabled returns whether the rule is enabled by default
+func (r *{{ .RuleNameCC }}Rule) Enabled() bool {
+	// TODO: Determine whether the rule is enabled by default
+	return true
+}
+
+// Severity returns the rule severity
+func (r *{{ .RuleNameCC }}Rule) Severity() string {
+	// TODO: Determine the rule's severiry
+	return tflint.ERROR
+}
+
+// Link returns the rule reference link
+func (r *{{ .RuleNameCC }}Rule) Link() string {
+	// TODO: If the rule is so trivial that no documentation is needed, return "" instead.
+	return project.ReferenceLink(r.Name())
+}
+
+// TODO: Write the details of the inspection
+// Check checks ...
+func (r *{{ .RuleNameCC }}Rule) Check(runner tflint.Runner) error {
+	// TODO: Write the implementation here. See this documentation for what tflint.Runner can do.
+	//       https://pkg.go.dev/github.com/terraform-linters/tflint-plugin-sdk/tflint#Runner
+
+	return runner.WalkResourceAttributes(r.resourceType, r.attributeName, func(attribute *hcl.Attribute) error {
+		var val string
+		err := runner.EvaluateExpr(attribute.Expr, &val, nil)
+
+		return runner.EnsureNoError(err, func() error {
+			if val == "" {
+				runner.EmitIssueOnExpr(
+					r,
+					"TODO",
+					attribute.Expr,
+				)
+			}
+			return nil
+		})
+	})
+}

rules/rule.go.tmpl

@@ -0,0 +1,47 @@
+package rules
+
+import (
+	"testing"
+
+	hcl "github.com/hashicorp/hcl/v2"
+	"github.com/terraform-linters/tflint-plugin-sdk/helper"
+)
+
+func Test_{{ .RuleNameCC }}(t *testing.T) {
+	cases := []struct {
+		Name     string
+		Content  string
+		Expected helper.Issues
+	}{
+		{
+			Name: "basic",
+			Content: `
+resource "null_resource" "null" {
+}
+`,
+			Expected: helper.Issues{
+				{
+					Rule:    New{{ .RuleNameCC }}Rule(),
+					Message: "TODO",
+					Range: hcl.Range{
+						Filename: "resource.tf",
+						Start:    hcl.Pos{Line: 0, Column: 0},
+						End:      hcl.Pos{Line: 0, Column: 0},
+					},
+				},
+			},
+		},
+	}
+
+	rule := New{{ .RuleNameCC }}Rule()
+
+	for _, tc := range cases {
+		runner := helper.TestRunner(t, map[string]string{"resource.tf": tc.Content})
+
+		if err := rule.Check(runner); err != nil {
+			t.Fatalf("Unexpected error occurred: %s", err)
+		}
+
+		helper.AssertIssues(t, tc.Expected, runner.Issues)
+	}
+}