Improve messaging when TF installation is not found

internal/langserver/errors/errors.go

@@ -0,0 +1,15 @@
+package errors
+
+import (
+	e "errors"
+
+	"github.com/hashicorp/terraform-ls/internal/terraform/module"
+)
+
+func EnrichTfExecError(err error) error {
+	if module.IsTerraformNotFound(err) {
+		return e.New("Terraform (CLI) is required. " +
+			"Please install Terraform or make it available in $PATH")
+	}
+	return err
+}

internal/langserver/handlers/command/init.go

@@ -7,6 +7,7 @@ import (
 	"github.com/creachadair/jrpc2/code"
 	lsctx "github.com/hashicorp/terraform-ls/internal/context"
 	"github.com/hashicorp/terraform-ls/internal/langserver/cmd"
+	"github.com/hashicorp/terraform-ls/internal/langserver/errors"
 	"github.com/hashicorp/terraform-ls/internal/langserver/progress"
 	ilsp "github.com/hashicorp/terraform-ls/internal/lsp"
 	lsp "github.com/hashicorp/terraform-ls/internal/protocol"
@@ -40,7 +41,7 @@ func TerraformInitHandler(ctx context.Context, args cmd.CommandArgs) (interface{
 
 	tfExec, err := module.TerraformExecutorForModule(ctx, mod)
 	if err != nil {
-		return nil, err
+		return nil, errors.EnrichTfExecError(err)
 	}
 
 	progress.Begin(ctx, "Initializing")

internal/langserver/handlers/command/validate.go

@@ -8,6 +8,7 @@ import (
 	lsctx "github.com/hashicorp/terraform-ls/internal/context"
 	"github.com/hashicorp/terraform-ls/internal/langserver/cmd"
 	"github.com/hashicorp/terraform-ls/internal/langserver/diagnostics"
+	"github.com/hashicorp/terraform-ls/internal/langserver/errors"
 	"github.com/hashicorp/terraform-ls/internal/langserver/progress"
 	ilsp "github.com/hashicorp/terraform-ls/internal/lsp"
 	lsp "github.com/hashicorp/terraform-ls/internal/protocol"
@@ -41,7 +42,7 @@ func TerraformValidateHandler(ctx context.Context, args cmd.CommandArgs) (interf
 
 	tfExec, err := module.TerraformExecutorForModule(ctx, mod)
 	if err != nil {
-		return nil, err
+		return nil, errors.EnrichTfExecError(err)
 	}
 
 	notifier, err := lsctx.Diagnostics(ctx)

internal/langserver/handlers/did_open.go

@@ -10,6 +10,7 @@ import (
 	"github.com/google/uuid"
 	lsctx "github.com/hashicorp/terraform-ls/internal/context"
 	"github.com/hashicorp/terraform-ls/internal/langserver/cmd"
+	"github.com/hashicorp/terraform-ls/internal/langserver/errors"
 	"github.com/hashicorp/terraform-ls/internal/langserver/handlers/command"
 	ilsp "github.com/hashicorp/terraform-ls/internal/lsp"
 	lsp "github.com/hashicorp/terraform-ls/internal/protocol"
@@ -89,9 +90,16 @@ func (lh *logHandler) TextDocumentDidOpen(ctx context.Context, params lsp.DidOpe
 		return err
 	}
 
+	_, tfExecErr := module.TerraformExecPath(ctx, mod)
+
 	if walker.IsWalking() || mod.ProviderSchemaState() == module.OpStateLoading {
 		// avoid raising false warnings if operations are still in-flight
 		lh.logger.Printf("walker has not finished walking yet, data may be inaccurate for %s", f.FullPath())
+	} else if tfExecErr != nil {
+		jrpc2.PushNotify(ctx, "window/showMessage", lsp.ShowMessageParams{
+			Type:    lsp.Error,
+			Message: errors.EnrichTfExecError(tfExecErr).Error(),
+		})
 	} else if len(sources) == 0 {
 		// TODO: Only notify once per f.Dir() per session
 		dh := ilsp.FileHandlerFromDirPath(f.Dir())

internal/langserver/handlers/formatting.go

@@ -5,6 +5,7 @@ import (
 
 	lsctx "github.com/hashicorp/terraform-ls/internal/context"
 	"github.com/hashicorp/terraform-ls/internal/hcl"
+	"github.com/hashicorp/terraform-ls/internal/langserver/errors"
 	ilsp "github.com/hashicorp/terraform-ls/internal/lsp"
 	lsp "github.com/hashicorp/terraform-ls/internal/protocol"
 	"github.com/hashicorp/terraform-ls/internal/terraform/module"
@@ -32,7 +33,7 @@ func (h *logHandler) TextDocumentFormatting(ctx context.Context, params lsp.Docu
 
 	tfExec, err := module.TerraformExecutorForModule(ctx, mod)
 	if err != nil {
-		return edits, err
+		return edits, errors.EnrichTfExecError(err)
 	}
 
 	file, err := fs.GetDocument(fh)

internal/terraform/module/errors.go

@@ -22,3 +22,17 @@ func IsModuleNotFound(err error) bool {
 	_, ok := err.(*ModuleNotFoundErr)
 	return ok
 }
+
+type NoTerraformExecPathErr struct{}
+
+func (NoTerraformExecPathErr) Error() string {
+	return "No exec path provided for terraform"
+}
+
+func IsTerraformNotFound(err error) bool {
+	if err == nil {
+		return false
+	}
+	_, ok := err.(NoTerraformExecPathErr)
+	return ok
+}

internal/terraform/module/terraform_executor.go

@@ -13,24 +13,17 @@ func TerraformExecutorForModule(ctx context.Context, mod Module) (exec.Terraform
 		return nil, fmt.Errorf("no terraform executor provided")
 	}
 
-	var tfExec exec.TerraformExecutor
-	var err error
+	execPath, err := TerraformExecPath(ctx, mod)
+	if err != nil {
+		return nil, err
+	}
 
-	opts, ok := exec.ExecutorOptsFromContext(ctx)
-	if ok && opts.ExecPath != "" {
-		tfExec, err = newExecutor(mod.Path(), opts.ExecPath)
-		if err != nil {
-			return nil, err
-		}
-	} else if mod.TerraformExecPath() != "" {
-		tfExec, err = newExecutor(mod.Path(), mod.TerraformExecPath())
-		if err != nil {
-			return nil, err
-		}
-	} else {
-		return nil, fmt.Errorf("no exec path provided for terraform")
+	tfExec, err := newExecutor(mod.Path(), execPath)
+	if err != nil {
+		return nil, err
 	}
 
+	opts, ok := exec.ExecutorOptsFromContext(ctx)
 	if ok && opts.ExecLogPath != "" {
 		tfExec.SetExecLogPath(opts.ExecLogPath)
 	}
@@ -40,3 +33,14 @@ func TerraformExecutorForModule(ctx context.Context, mod Module) (exec.Terraform
 
 	return tfExec, nil
 }
+
+func TerraformExecPath(ctx context.Context, mod Module) (string, error) {
+	opts, ok := exec.ExecutorOptsFromContext(ctx)
+	if ok && opts.ExecPath != "" {
+		return opts.ExecPath, nil
+	} else if mod.TerraformExecPath() != "" {
+		return mod.TerraformExecPath(), nil
+	} else {
+		return "", NoTerraformExecPathErr{}
+	}
+}