feat: improve terraform template parsing errors (#2331)

provisioner/terraform/parse.go

@@ -2,9 +2,13 @@ package terraform
 
 import (
 	"encoding/json"
+	"fmt"
 	"os"
+	"path/filepath"
+	"strings"
 
 	"github.com/hashicorp/terraform-config-inspect/tfconfig"
+	"github.com/mitchellh/go-wordwrap"
 	"golang.org/x/xerrors"
 
 	"github.com/coder/coder/provisionersdk/proto"
@@ -12,14 +16,12 @@ import (
 
 // Parse extracts Terraform variables from source-code.
 func (*terraform) Parse(request *proto.Parse_Request, stream proto.DRPCProvisioner_ParseStream) error {
-	defer func() {
-		_ = stream.CloseSend()
-	}()
-
+	// Load the module and print any parse errors.
 	module, diags := tfconfig.LoadModule(request.Directory)
 	if diags.HasErrors() {
-		return xerrors.Errorf("load module: %w", diags.Err())
+		return xerrors.Errorf("load module: %s", formatDiagnostics(request.Directory, diags))
 	}
+
 	parameters := make([]*proto.ParameterSchema, 0, len(module.Variables))
 	for _, v := range module.Variables {
 		schema, err := convertVariableToParameter(v)
@@ -83,3 +85,47 @@ func convertVariableToParameter(variable *tfconfig.Variable) (*proto.ParameterSc
 
 	return schema, nil
 }
+
+// formatDiagnostics returns a nicely formatted string containing all of the
+// error details within the tfconfig.Diagnostics. We need to use this because
+// the default format doesn't provide much useful information.
+func formatDiagnostics(baseDir string, diags tfconfig.Diagnostics) string {
+	var msgs strings.Builder
+	for _, d := range diags {
+		// Convert severity.
+		severity := "UNKNOWN SEVERITY"
+		switch {
+		case d.Severity == tfconfig.DiagError:
+			severity = "ERROR"
+		case d.Severity == tfconfig.DiagWarning:
+			severity = "WARN"
+		}
+
+		// Determine filepath and line
+		location := "unknown location"
+		if d.Pos != nil {
+			filename, err := filepath.Rel(baseDir, d.Pos.Filename)
+			if err != nil {
+				filename = d.Pos.Filename
+			}
+			location = fmt.Sprintf("%s:%d", filename, d.Pos.Line)
+		}
+
+		_, _ = msgs.WriteString(fmt.Sprintf("\n%s: %s (%s)\n", severity, d.Summary, location))
+
+		// Wrap the details to 80 characters and indent them.
+		if d.Detail != "" {
+			wrapped := wordwrap.WrapString(d.Detail, 78)
+			for _, line := range strings.Split(wrapped, "\n") {
+				_, _ = msgs.WriteString(fmt.Sprintf("> %s\n", line))
+			}
+		}
+	}
+
+	spacer := " "
+	if len(diags) > 1 {
+		spacer = "\n\n"
+	}
+
+	return spacer + strings.TrimSpace(msgs.String())
+}