Add WalkExpressions function (#181)

Author: wata727

helper/runner.go

@@ -5,6 +5,7 @@ import (
 	"os"
 
 	"github.com/hashicorp/hcl/v2"
+	"github.com/hashicorp/hcl/v2/hclsyntax"
 	"github.com/terraform-linters/tflint-plugin-sdk/hclext"
 	"github.com/terraform-linters/tflint-plugin-sdk/terraform/addrs"
 	"github.com/terraform-linters/tflint-plugin-sdk/tflint"
@@ -124,6 +125,52 @@ func (r *Runner) GetFiles() (map[string]*hcl.File, error) {
 	return r.files, nil
 }
 
+type nativeWalker struct {
+	walker tflint.ExprWalker
+}
+
+func (w *nativeWalker) Enter(node hclsyntax.Node) hcl.Diagnostics {
+	if expr, ok := node.(hcl.Expression); ok {
+		return w.walker.Enter(expr)
+	}
+	return nil
+}
+
+func (w *nativeWalker) Exit(node hclsyntax.Node) hcl.Diagnostics {
+	if expr, ok := node.(hcl.Expression); ok {
+		return w.walker.Exit(expr)
+	}
+	return nil
+}
+
+// WalkExpressions traverses expressions in all files by the passed walker.
+func (r *Runner) WalkExpressions(walker tflint.ExprWalker) hcl.Diagnostics {
+	diags := hcl.Diagnostics{}
+	for _, file := range r.files {
+		if body, ok := file.Body.(*hclsyntax.Body); ok {
+			walkDiags := hclsyntax.Walk(body, &nativeWalker{walker: walker})
+			diags = diags.Extend(walkDiags)
+			continue
+		}
+
+		// In JSON syntax, everything can be walked as an attribute.
+		attrs, jsonDiags := file.Body.JustAttributes()
+		if jsonDiags.HasErrors() {
+			diags = diags.Extend(jsonDiags)
+			continue
+		}
+
+		for _, attr := range attrs {
+			enterDiags := walker.Enter(attr.Expr)
+			diags = diags.Extend(enterDiags)
+			exitDiags := walker.Exit(attr.Expr)
+			diags = diags.Extend(exitDiags)
+		}
+	}
+
+	return diags
+}
+
 // DecodeRuleConfig extracts the rule's configuration into the given value
 func (r *Runner) DecodeRuleConfig(name string, ret interface{}) error {
 	schema := hclext.ImpliedBodySchema(ret)

helper/runner_test.go

@@ -280,6 +280,221 @@ func Test_GetModuleContent_json(t *testing.T) {
 	}
 }
 
+func TestWalkExpressions(t *testing.T) {
+	tests := []struct {
+		name   string
+		files  map[string]string
+		walked []hcl.Range
+	}{
+		{
+			name: "resource",
+			files: map[string]string{
+				"resource.tf": `
+resource "null_resource" "test" {
+  key = "foo"
+}`,
+			},
+			walked: []hcl.Range{
+				{Start: hcl.Pos{Line: 3, Column: 9}, End: hcl.Pos{Line: 3, Column: 14}},
+				{Start: hcl.Pos{Line: 3, Column: 10}, End: hcl.Pos{Line: 3, Column: 13}},
+			},
+		},
+		{
+			name: "data source",
+			files: map[string]string{
+				"data.tf": `
+data "null_dataresource" "test" {
+  key = "foo"
+}`,
+			},
+			walked: []hcl.Range{
+				{Start: hcl.Pos{Line: 3, Column: 9}, End: hcl.Pos{Line: 3, Column: 14}},
+				{Start: hcl.Pos{Line: 3, Column: 10}, End: hcl.Pos{Line: 3, Column: 13}},
+			},
+		},
+		{
+			name: "module call",
+			files: map[string]string{
+				"module.tf": `
+module "m" {
+  source = "./module"
+  key    = "foo"
+}`,
+			},
+			walked: []hcl.Range{
+				{Start: hcl.Pos{Line: 3, Column: 12}, End: hcl.Pos{Line: 3, Column: 22}},
+				{Start: hcl.Pos{Line: 3, Column: 13}, End: hcl.Pos{Line: 3, Column: 21}},
+				{Start: hcl.Pos{Line: 4, Column: 12}, End: hcl.Pos{Line: 4, Column: 17}},
+				{Start: hcl.Pos{Line: 4, Column: 13}, End: hcl.Pos{Line: 4, Column: 16}},
+			},
+		},
+		{
+			name: "provider config",
+			files: map[string]string{
+				"provider.tf": `
+provider "p" {
+  key = "foo"
+}`,
+			},
+			walked: []hcl.Range{
+				{Start: hcl.Pos{Line: 3, Column: 9}, End: hcl.Pos{Line: 3, Column: 14}},
+				{Start: hcl.Pos{Line: 3, Column: 10}, End: hcl.Pos{Line: 3, Column: 13}},
+			},
+		},
+		{
+			name: "locals",
+			files: map[string]string{
+				"locals.tf": `
+locals {
+  key = "foo"
+}`,
+			},
+			walked: []hcl.Range{
+				{Start: hcl.Pos{Line: 3, Column: 9}, End: hcl.Pos{Line: 3, Column: 14}},
+				{Start: hcl.Pos{Line: 3, Column: 10}, End: hcl.Pos{Line: 3, Column: 13}},
+			},
+		},
+		{
+			name: "output",
+			files: map[string]string{
+				"output.tf": `
+output "o" {
+  value = "foo"
+}`,
+			},
+			walked: []hcl.Range{
+				{Start: hcl.Pos{Line: 3, Column: 11}, End: hcl.Pos{Line: 3, Column: 16}},
+				{Start: hcl.Pos{Line: 3, Column: 12}, End: hcl.Pos{Line: 3, Column: 15}},
+			},
+		},
+		{
+			name: "resource with block",
+			files: map[string]string{
+				"resource.tf": `
+resource "null_resource" "test" {
+  key = "foo"
+
+  lifecycle {
+    ignore_changes = [key]
+  }
+}`,
+			},
+			walked: []hcl.Range{
+				{Start: hcl.Pos{Line: 3, Column: 9}, End: hcl.Pos{Line: 3, Column: 14}},
+				{Start: hcl.Pos{Line: 3, Column: 10}, End: hcl.Pos{Line: 3, Column: 13}},
+				{Start: hcl.Pos{Line: 6, Column: 22}, End: hcl.Pos{Line: 6, Column: 27}},
+				{Start: hcl.Pos{Line: 6, Column: 23}, End: hcl.Pos{Line: 6, Column: 26}},
+			},
+		},
+		{
+			name: "resource json",
+			files: map[string]string{
+				"resource.tf.json": `
+{
+  "resource": {
+    "null_resource": {
+      "test": {
+        "key": "foo",
+        "nested": {
+          "key": "foo"
+        },
+        "list": [{
+          "key": "foo"
+        }]
+      }
+    }
+  }
+}`,
+			},
+			walked: []hcl.Range{
+				{Start: hcl.Pos{Line: 3, Column: 15}, End: hcl.Pos{Line: 15, Column: 4}},
+			},
+		},
+		{
+			name: "multiple files",
+			files: map[string]string{
+				"main.tf": `
+provider "aws" {
+  region = "us-east-1"
+
+  assume_role {
+    role_arn = "arn:aws:iam::123412341234:role/ExampleRole"
+  }
+}`,
+				"main_override.tf": `
+provider "aws" {
+  region = "us-east-1"
+
+  assume_role {
+    role_arn = null
+  }
+}`,
+			},
+			walked: []hcl.Range{
+				{Start: hcl.Pos{Line: 3, Column: 12}, End: hcl.Pos{Line: 3, Column: 23}, Filename: "main.tf"},
+				{Start: hcl.Pos{Line: 3, Column: 13}, End: hcl.Pos{Line: 3, Column: 22}, Filename: "main.tf"},
+				{Start: hcl.Pos{Line: 6, Column: 16}, End: hcl.Pos{Line: 6, Column: 60}, Filename: "main.tf"},
+				{Start: hcl.Pos{Line: 6, Column: 17}, End: hcl.Pos{Line: 6, Column: 59}, Filename: "main.tf"},
+				{Start: hcl.Pos{Line: 3, Column: 12}, End: hcl.Pos{Line: 3, Column: 23}, Filename: "main_override.tf"},
+				{Start: hcl.Pos{Line: 3, Column: 13}, End: hcl.Pos{Line: 3, Column: 22}, Filename: "main_override.tf"},
+				{Start: hcl.Pos{Line: 6, Column: 16}, End: hcl.Pos{Line: 6, Column: 20}, Filename: "main_override.tf"},
+			},
+		},
+		{
+			name: "nested attributes",
+			files: map[string]string{
+				"data.tf": `
+data "terraform_remote_state" "remote_state" {
+  backend = "remote"
+
+  config = {
+    organization = "Organization"
+    workspaces = {
+      name = "${var.environment}"
+    }
+  }
+}`,
+			},
+			walked: []hcl.Range{
+				{Start: hcl.Pos{Line: 3, Column: 13}, End: hcl.Pos{Line: 3, Column: 21}},
+				{Start: hcl.Pos{Line: 3, Column: 14}, End: hcl.Pos{Line: 3, Column: 20}},
+				{Start: hcl.Pos{Line: 5, Column: 12}, End: hcl.Pos{Line: 10, Column: 4}},
+				{Start: hcl.Pos{Line: 6, Column: 5}, End: hcl.Pos{Line: 6, Column: 17}},
+				{Start: hcl.Pos{Line: 6, Column: 20}, End: hcl.Pos{Line: 6, Column: 34}},
+				{Start: hcl.Pos{Line: 6, Column: 21}, End: hcl.Pos{Line: 6, Column: 33}},
+				{Start: hcl.Pos{Line: 7, Column: 5}, End: hcl.Pos{Line: 7, Column: 15}},
+				{Start: hcl.Pos{Line: 7, Column: 18}, End: hcl.Pos{Line: 9, Column: 6}},
+				{Start: hcl.Pos{Line: 8, Column: 7}, End: hcl.Pos{Line: 8, Column: 11}},
+				{Start: hcl.Pos{Line: 8, Column: 14}, End: hcl.Pos{Line: 8, Column: 34}},
+				{Start: hcl.Pos{Line: 8, Column: 17}, End: hcl.Pos{Line: 8, Column: 32}},
+			},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			runner := TestRunner(t, test.files)
+
+			walked := []hcl.Range{}
+			diags := runner.WalkExpressions(tflint.ExprWalkFunc(func(expr hcl.Expression) hcl.Diagnostics {
+				walked = append(walked, expr.Range())
+				return nil
+			}))
+			if diags.HasErrors() {
+				t.Fatal(diags)
+			}
+			opts := cmp.Options{
+				cmpopts.IgnoreFields(hcl.Range{}, "Filename"),
+				cmpopts.IgnoreFields(hcl.Pos{}, "Byte"),
+				cmpopts.SortSlices(func(x, y hcl.Range) bool { return x.String() > y.String() }),
+			}
+			if diff := cmp.Diff(walked, test.walked, opts); diff != "" {
+				t.Error(diff)
+			}
+		})
+	}
+}
+
 func Test_DecodeRuleConfig(t *testing.T) {
 	files := map[string]string{
 		".tflint.hcl": `

plugin/plugin2host/client.go

@@ -165,6 +165,72 @@ func (c *GRPCClient) GetFiles() (map[string]*hcl.File, error) {
 	return files, nil
 }
 
+type nativeWalker struct {
+	walker tflint.ExprWalker
+}
+
+func (w *nativeWalker) Enter(node hclsyntax.Node) hcl.Diagnostics {
+	if expr, ok := node.(hcl.Expression); ok {
+		return w.walker.Enter(expr)
+	}
+	return nil
+}
+
+func (w *nativeWalker) Exit(node hclsyntax.Node) hcl.Diagnostics {
+	if expr, ok := node.(hcl.Expression); ok {
+		return w.walker.Exit(expr)
+	}
+	return nil
+}
+
+// WalkExpressions traverses expressions in all files by the passed walker.
+// Note that it behaves differently in native HCL syntax and JSON syntax.
+//
+// In the HCL syntax, `var.foo` and `var.bar` in `[var.foo, var.bar]` are
+// also passed to the walker. In other words, it traverses expressions recursively.
+// To avoid redundant checks, the walker should check the kind of expression.
+//
+// In the JSON syntax, only an expression of an attribute seen from the top
+// level of the file is passed. In other words, it doesn't traverse expressions
+// recursively. This is a limitation of JSON syntax.
+func (c *GRPCClient) WalkExpressions(walker tflint.ExprWalker) hcl.Diagnostics {
+	files, err := c.GetFiles()
+	if err != nil {
+		return hcl.Diagnostics{
+			{
+				Severity: hcl.DiagError,
+				Summary:  "failed to call GetFiles()",
+				Detail:   err.Error(),
+			},
+		}
+	}
+
+	diags := hcl.Diagnostics{}
+	for _, file := range files {
+		if body, ok := file.Body.(*hclsyntax.Body); ok {
+			walkDiags := hclsyntax.Walk(body, &nativeWalker{walker: walker})
+			diags = diags.Extend(walkDiags)
+			continue
+		}
+
+		// In JSON syntax, everything can be walked as an attribute.
+		attrs, jsonDiags := file.Body.JustAttributes()
+		if jsonDiags.HasErrors() {
+			diags = diags.Extend(jsonDiags)
+			continue
+		}
+
+		for _, attr := range attrs {
+			enterDiags := walker.Enter(attr.Expr)
+			diags = diags.Extend(enterDiags)
+			exitDiags := walker.Exit(attr.Expr)
+			diags = diags.Extend(exitDiags)
+		}
+	}
+
+	return diags
+}
+
 // DecodeRuleConfig guesses the schema of the rule config from the passed interface and sends the schema to GRPC server.
 // Content retrieved based on the schema is decoded into the passed interface.
 func (c *GRPCClient) DecodeRuleConfig(name string, ret interface{}) error {