chore: add warnings if modules are missing

CONTRIBUTING.md

@@ -6,3 +6,4 @@ To run preview:
 2. `pnpm install`
 3. `cd ..`
 4. `go run ./cmd/preview/main.go web --pnpm=site`
+5. visit http://localhost:5173/?testcontrols=true

preview_test.go

@@ -5,8 +5,11 @@ import (
 	"encoding/json"
 	"os"
 	"path/filepath"
+	"regexp"
+	"slices"
 	"testing"
 
+	"github.com/hashicorp/hcl/v2"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
@@ -38,6 +41,7 @@ func Test_Extract(t *testing.T) {
 		expTags     map[string]string
 		unknownTags []string
 		params      map[string]assertParam
+		warnings    []*regexp.Regexp
 	}{
 		{
 			name:        "bad param values",
@@ -402,6 +406,19 @@ func Test_Extract(t *testing.T) {
 				"beta":  ap().unknown(),
 			},
 		},
+		{
+			name:    "missing_module",
+			dir:     "missingmodule",
+			expTags: map[string]string{},
+			input: preview.Input{
+				ParameterValues: map[string]string{},
+			},
+			unknownTags: []string{},
+			params:      map[string]assertParam{},
+			warnings: []*regexp.Regexp{
+				regexp.MustCompile("Module not loaded"),
+			},
+		},
 		{
 			skip:    "skip until https://github.com/aquasecurity/trivy/pull/8479 is resolved",
 			name:    "submodcount",
@@ -440,6 +457,16 @@ func Test_Extract(t *testing.T) {
 			}
 			require.False(t, diags.HasErrors())
 
+			if len(tc.warnings) > 0 {
+				for _, w := range tc.warnings {
+					idx := slices.IndexFunc(diags, func(diagnostic *hcl.Diagnostic) bool {
+						return w.MatchString(diagnostic.Error())
+
+					})
+					require.Greater(t, idx, -1, "expected warning %q to be present in diags", w.String())
+				}
+			}
+
 			// Assert tags
 			validTags := output.WorkspaceTags.Tags()
 

testdata/missingmodule/main.tf

@@ -0,0 +1,12 @@
+module "does-not-exist" {
+  source         = "registry.coder.com/modules/does-not-exist/coder"
+}
+
+module "does-not-exist-2" {
+  count = 0
+  source         = "registry.coder.com/modules/does-not-exist/coder"
+}
+
+module "one" {
+  source = "./one"
+}

testdata/missingmodule/one/one.tf

@@ -0,0 +1,3 @@
+module "onea" {
+  source = "./onea"
+}

testdata/missingmodule/one/onea/onea.tf

@@ -0,0 +1,14 @@
+terraform {
+  required_providers {
+    coder = {
+      source = "coder/coder"
+      version = "2.4.0-pre0"
+    }
+  }
+}
+
+data "null_data_source" "values" {
+  inputs = {
+    foo = "bar"
+  }
+}

testdata/missingmodule/skipe2e

@@ -0,0 +1 @@
+Not a real module

warnings.go

@@ -11,6 +11,57 @@ import (
 func warnings(modules terraform.Modules) hcl.Diagnostics {
 	var diags hcl.Diagnostics
 	diags = diags.Extend(unexpandedCountBlocks(modules))
+	diags = diags.Extend(unresolvedModules(modules))
+
+	return diags
+}
+
+// unresolvedModules does a best effort to try and detect if some modules
+// failed to resolve. This is usually because `terraform init` is not run.
+func unresolvedModules(modules terraform.Modules) hcl.Diagnostics {
+	var diags hcl.Diagnostics
+	modulesUsed := make(map[string]bool)
+	modulesByID := make(map[string]*terraform.Block)
+
+	// There is no easy way to know if a `module` failed to resolve. The failure is
+	// only logged in the trivy package. No errors are returned to the caller. So
+	// instead this code will infer a failed resolution by checking if any blocks
+	// exist that reference each `module` block. This will work as long as the module
+	// has some content. If a module is completely empty, then it will be detected as
+	// "not loaded".
+	blocks := modules.GetBlocks()
+	for _, block := range blocks {
+		if block.InModule() && block.ModuleBlock() != nil {
+			modulesUsed[block.ModuleBlock().ID()] = true
+		}
+
+		if block.Type() == "module" {
+			modulesByID[block.ID()] = block
+			_, ok := modulesUsed[block.ID()]
+			if !ok {
+				modulesUsed[block.ID()] = false
+			}
+		}
+	}
+
+	for id, v := range modulesUsed {
+		if !v {
+			block, ok := modulesByID[id]
+			if ok {
+				label := block.Type()
+				for _, l := range block.Labels() {
+					label += " " + fmt.Sprintf("%q", l)
+				}
+
+				diags = diags.Append(&hcl.Diagnostic{
+					Severity: hcl.DiagWarning,
+					Summary:  "Module not loaded, did you run `terraform init`? Or maybe the module is empty.",
+					Detail:   fmt.Sprintf("Module '%s' in file %q cannot be resolved. This module will be ignored.", label, block.HCLBlock().DefRange),
+					Subject:  &(block.HCLBlock().DefRange),
+				})
+			}
+		}
+	}
 
 	return diags
 }