Handle TF drift more gracefully for ti_resource_group and ti_resource_group_assignment (#5)

[This
article](https://www.hashicorp.com/blog/writing-custom-terraform-providers)
provides a good initial explanation of the expected behaviors of the
different CRUD methods for a resource.

In it, it mentions that the `Read` method should be able to gracefully
handle when the resource no longer exists (probably due to manual
deletion).

I also fixed a bug where `resourceGroup` was supposed to be
`resource_group` and also modified `petoju` --> `zph` in certain places.
This makes error logs a bit more clear.

---------

Co-authored-by: Andrew Chen <andrewchen@plaid.com>

Author: otherchen

Diff for: go.mod

@@ -1,4 +1,4 @@
-module github.com/petoju/terraform-provider-mysql/v3
+module github.com/zph/terraform-provider-mysql/v3
 
 require (
 	cloud.google.com/go/cloudsqlconn v1.11.0

Diff for: main.go

@@ -2,7 +2,7 @@ package main
 
 import (
 	"github.com/hashicorp/terraform-plugin-sdk/v2/plugin"
-	"github.com/petoju/terraform-provider-mysql/v3/mysql"
+	"github.com/zph/terraform-provider-mysql/v3/mysql"
 )
 
 func main() {

Diff for: mysql/resource_ti_resource_group.go

@@ -5,6 +5,7 @@ import (
 	"database/sql"
 	"errors"
 	"fmt"
+	"log"
 	"strings"
 
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
@@ -172,12 +173,14 @@ func ReadResourceGroup(ctx context.Context, d *schema.ResourceData, meta interfa
 		return diag.Errorf("error during get resource group (%s): %s", d.Id(), err)
 	}
 
-	if err != nil {
+	// If we're not able to find the resource group, assume that there's terraform
+	// diff and allow terraform to recreate it instead of throwing an error.
+	if rg == nil {
 		d.SetId("")
-		return diag.Errorf(`error converting burstable value from tidb %e`, err)
+		return nil
 	}
 
-	setResourceGroupOnResourceData(rg, d)
+	setResourceGroupOnResourceData(*rg, d)
 	return nil
 }
 
@@ -188,7 +191,7 @@ func DeleteResourceGroup(ctx context.Context, d *schema.ResourceData, meta inter
 	if err != nil {
 		return diag.FromErr(err)
 	}
-	// TODO: check for users assigned as safety? and assert zero?
+
 	deleteQuery := fmt.Sprintf("DROP RESOURCE GROUP IF EXISTS %s", name)
 	_, err = db.Exec(deleteQuery)
 	if err != nil && !errors.Is(err, sql.ErrNoRows) {
@@ -199,7 +202,7 @@ func DeleteResourceGroup(ctx context.Context, d *schema.ResourceData, meta inter
 	return nil
 }
 
-func getResourceGroupFromDB(db *sql.DB, name string) (ResourceGroup, error) {
+func getResourceGroupFromDB(db *sql.DB, name string) (*ResourceGroup, error) {
 	rg := ResourceGroup{Name: name}
 
 	/*
@@ -216,12 +219,13 @@ func getResourceGroupFromDB(db *sql.DB, name string) (ResourceGroup, error) {
 
 	err := db.QueryRow(query, name).Scan(&rg.Name, &rg.ResourceUnits, &rg.Priority, &rg.Burstable, &rg.QueryLimit)
 	if errors.Is(err, sql.ErrNoRows) {
-		return ResourceGroup{}, fmt.Errorf("resource group doesn't exist (%s): %s", name, err)
+		log.Printf("[DEBUG] resource group doesn't exist (%s): %s", name, err)
+		return nil, nil
 	} else if err != nil {
-		return ResourceGroup{}, fmt.Errorf("error during get resource group (%s): %s", name, err)
+		return nil, fmt.Errorf("error during get resource group (%s): %s", name, err)
 	}
 
-	return rg, nil
+	return &rg, nil
 }
 
 func NewResourceGroupFromResourceData(d *schema.ResourceData) ResourceGroup {

Diff for: mysql/resource_ti_resource_group_user_assignment.go

@@ -48,10 +48,15 @@ func CreateOrUpdateResourceGroupUser(ctx context.Context, d *schema.ResourceData
 	var warnLevel, warnMessage string
 	var warnCode int = 0
 
-	_, _, err = readUserFromDB(db, user)
+	currentUser, _, err := readUserFromDB(db, user)
 	if err != nil {
 		d.SetId("")
-		return diag.Errorf(`must create user first before assigning to resource group | getting user %s | error %s`, user, err)
+		return diag.Errorf(`error during get user (%s): %s`, user, err)
+	}
+
+	if currentUser == "" {
+		d.SetId("")
+		return diag.Errorf(`must create user first before assigning to resource group | getting user %s | error %s`, currentUser, err)
 	}
 
 	sql := fmt.Sprintf("ALTER USER `%s` RESOURCE GROUP `%s`", user, resourceGroup)
@@ -88,8 +93,15 @@ func ReadResourceGroupUser(ctx context.Context, d *schema.ResourceData, meta int
 		return diag.Errorf(`error getting user %s`, err)
 	}
 
+	// If the user doesn't exist, instead of erroring, recognize that there's
+	// terraform drift and attempt to create the assignment again.
+	if user == "" {
+		d.SetId("")
+		return nil
+	}
+
 	d.Set("user", user)
-	d.Set("resourceGroup", resourceGroup)
+	d.Set("resource_group", resourceGroup)
 
 	return nil
 }
@@ -102,6 +114,7 @@ func DeleteResourceGroupUser(ctx context.Context, d *schema.ResourceData, meta i
 	if err != nil {
 		return diag.FromErr(err)
 	}
+
 	deleteQuery := fmt.Sprintf("ALTER USER `%s` RESOURCE GROUP `default`", user)
 	_, err = db.Exec(deleteQuery)
 	if err != nil && !errors.Is(err, sql.ErrNoRows) {
@@ -120,7 +133,8 @@ func readUserFromDB(db *sql.DB, name string) (string, string, error) {
 
 	err := row.Scan(&user, &resourceGroup)
 	if errors.Is(err, sql.ErrNoRows) {
-		return "", "", sql.ErrNoRows
+		log.Printf("[DEBUG] resource group doesn't exist (%s): %s", name, err)
+		return "", "", nil
 	} else if err != nil {
 		return "", "", fmt.Errorf(`error fetching user %e`, err)
 	}