Fix issues caused by multiple terraform blocks

See also #205

Some rules that reference terraform blocks do not assume that
blocks can be defined multiple times and can lead to inconsistent results in that case.

Author: wata727

rules/terraform_required_providers.go

@@ -151,7 +151,9 @@ func (r *TerraformRequiredProvidersRule) Check(rr tflint.Runner) error {
 	requiredProviders := hclext.Attributes{}
 	for _, terraform := range body.Blocks {
 		for _, requiredProvidersBlock := range terraform.Body.Blocks {
-			requiredProviders = requiredProvidersBlock.Body.Attributes
+			for name, attr := range requiredProvidersBlock.Body.Attributes {
+				requiredProviders[name] = attr
+			}
 		}
 	}
 

rules/terraform_required_providers_test.go

@@ -570,6 +570,108 @@ output "foo" {
 				},
 			},
 		},
+		{
+			Name: "multiple required providers",
+			Content: `
+terraform {
+  required_providers {
+    template = "~> 2"
+  }
+
+  required_providers {
+    aws = "~> 5.0"
+  }
+}
+
+provider "template" {}
+provider "aws" {}
+provider "google" {}
+
+terraform {
+  required_providers {
+    google = "~> 6.0"
+  }
+}
+`,
+			Expected: helper.Issues{
+				// FIXME: ignore order of issues
+				{
+					Rule:    NewTerraformRequiredProvidersRule(),
+					Message: "Legacy version constraint for provider \"template\" in `required_providers`",
+					Range: hcl.Range{
+						Filename: "module.tf",
+						Start: hcl.Pos{
+							Line:   4,
+							Column: 16,
+						},
+						End: hcl.Pos{
+							Line:   4,
+							Column: 22,
+						},
+					},
+				},
+				{
+					Rule:    NewTerraformRequiredProvidersRule(),
+					Message: "Legacy version constraint for provider \"aws\" in `required_providers`",
+					Range: hcl.Range{
+						Filename: "module.tf",
+						Start: hcl.Pos{
+							Line:   8,
+							Column: 11,
+						},
+						End: hcl.Pos{
+							Line:   8,
+							Column: 19,
+						},
+					},
+				},
+				{
+					Rule:    NewTerraformRequiredProvidersRule(),
+					Message: "Legacy version constraint for provider \"google\" in `required_providers`",
+					Range: hcl.Range{
+						Filename: "module.tf",
+						Start: hcl.Pos{
+							Line:   18,
+							Column: 14,
+						},
+						End: hcl.Pos{
+							Line:   18,
+							Column: 22,
+						},
+					},
+				},
+			},
+			Fixed: `
+terraform {
+  required_providers {
+    template = {
+      source  = "hashicorp/template"
+      version = "~> 2"
+    }
+  }
+
+  required_providers {
+    aws = {
+      source  = "hashicorp/aws"
+      version = "~> 5.0"
+    }
+  }
+}
+
+provider "template" {}
+provider "aws" {}
+provider "google" {}
+
+terraform {
+  required_providers {
+    google = {
+      source  = "hashicorp/google"
+      version = "~> 6.0"
+    }
+  }
+}
+`,
+		},
 	}
 
 	rule := NewTerraformRequiredProvidersRule()

rules/terraform_unused_required_providers.go

@@ -83,6 +83,7 @@ func (r *TerraformUnusedRequiredProvidersRule) Check(rr tflint.Runner) error {
 
 			for _, block := range content.Blocks {
 				var attrDiags hcl.Diagnostics
+				// FIXME: required providers should be merged
 				requiredProviders, attrDiags = block.Body.JustAttributes()
 				diags = diags.Extend(attrDiags)
 				if diags.HasErrors() {

rules/terraform_workspace_remote.go

@@ -98,6 +98,7 @@ func (r *TerraformWorkspaceRemoteRule) Check(runner tflint.Runner) error {
 	for _, terraform := range body.Blocks {
 		for _, requiredVersion := range terraform.Body.Attributes {
 			err := runner.EvaluateExpr(requiredVersion.Expr, func(v string) error {
+				// FIXME: Should constraints defined in multiple blocks be merged?
 				constraints, err := version.NewConstraint(v)
 				if err != nil {
 					return err