Override exactly according to the Terraform spec

integrationtest/inspection/override/.tflint.hcl

@@ -1,3 +1,7 @@
 plugin "testing" {
   enabled = true
 }
+
+rule "terraform_required_providers" {
+  enabled = true
+}

integrationtest/inspection/override/result.json

@@ -1,5 +1,25 @@
 {
   "issues": [
+    {
+      "rule": {
+        "name": "terraform_required_providers",
+        "severity": "error",
+        "link": ""
+      },
+      "message": "required_providers: aws=2,azurerm=1,google=3,oracle=2",
+      "range": {
+        "filename": "template.tf",
+        "start": {
+          "line": 11,
+          "column": 3
+        },
+        "end": {
+          "line": 11,
+          "column": 21
+        }
+      },
+      "callers": []
+    },
     {
       "rule": {
         "name": "aws_instance_example_type",

integrationtest/inspection/override/template.tf

@@ -2,3 +2,15 @@ resource "aws_instance" "web" {
   ami           = "ami-12345678"
   instance_type = "t2.micro" // Override by `template_override.tf`
 }
+
+terraform {
+  backend "s3" {}
+}
+
+terraform {
+  required_providers {
+    aws     = "1" // Override by `template_override.tf`
+    google  = "1" // Override by `version_override.tf`
+    azurerm = "1"
+  }
+}

integrationtest/inspection/override/template_override.tf

@@ -3,3 +3,11 @@ resource "aws_instance" "web" {
   instance_type        = "m5.2xlarge" // aws_instance_example_type
   iam_instance_profile = "web-server"
 }
+
+terraform {
+  required_providers {
+    aws     = "2"
+    google  = "2"
+    oracle  = "2"
+  }
+}

integrationtest/inspection/override/version_override.tf

@@ -0,0 +1,5 @@
+terraform {
+  required_providers {
+    google = "3"
+  }
+}

plugin/stub-generator/sources/testing/main.go

@@ -27,6 +27,7 @@ func main() {
 				rules.NewTerraformAutofixRemoveLocalRule(), // should be former than terraform_autofix_comment because this rule changes the line number
 				rules.NewTerraformAutofixCommentRule(),
 				rules.NewAwsInstanceAutofixConflictRule(), // should be later than terraform_autofix_comment because this rule adds an issue for terraform_autofix_comment
+				rules.NewTerraformRequiredProvidersRule(),
 			},
 		},
 	})

plugin/stub-generator/sources/testing/rules/terraform_required_providers.go

@@ -0,0 +1,87 @@
+package rules
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+
+	"github.com/terraform-linters/tflint-plugin-sdk/hclext"
+	"github.com/terraform-linters/tflint-plugin-sdk/tflint"
+)
+
+// TerraformRequiredProviders checks whether ...
+type TerraformRequiredProviders struct {
+	tflint.DefaultRule
+}
+
+// NewTerraformRequiredProvidersRule returns a new rule
+func NewTerraformRequiredProvidersRule() *TerraformRequiredProviders {
+	return &TerraformRequiredProviders{}
+}
+
+// Name returns the rule name
+func (r *TerraformRequiredProviders) Name() string {
+	return "terraform_required_providers"
+}
+
+// Enabled returns whether the rule is enabled by default
+func (r *TerraformRequiredProviders) Enabled() bool {
+	return false
+}
+
+// Severity returns the rule severity
+func (r *TerraformRequiredProviders) Severity() tflint.Severity {
+	return tflint.ERROR
+}
+
+// Link returns the rule reference link
+func (r *TerraformRequiredProviders) Link() string {
+	return ""
+}
+
+// Check checks whether ...
+func (r *TerraformRequiredProviders) Check(runner tflint.Runner) error {
+	module, err := runner.GetModuleContent(&hclext.BodySchema{
+		Blocks: []hclext.BlockSchema{
+			{
+				Type: "terraform",
+				Body: &hclext.BodySchema{
+					Blocks: []hclext.BlockSchema{
+						{
+							Type: "required_providers",
+							Body: &hclext.BodySchema{Mode: hclext.SchemaJustAttributesMode},
+						},
+					},
+				},
+			},
+		},
+	}, nil)
+	if err != nil {
+		return err
+	}
+
+	for _, terraform := range module.Blocks {
+		for _, requiredProvider := range terraform.Body.Blocks {
+			ret := []string{}
+			for name, attr := range requiredProvider.Body.Attributes {
+				v, diags := attr.Expr.Value(nil)
+				if diags.HasErrors() {
+					return diags
+				}
+				ret = append(ret, fmt.Sprintf("%s=%s", name, v.AsString()))
+			}
+			sort.Strings(ret)
+
+			err := runner.EmitIssue(
+				r,
+				fmt.Sprintf("required_providers: %s", strings.Join(ret, ",")),
+				requiredProvider.DefRange,
+			)
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}