fix: Better error message for dashboard import (#7621)

Common mistake is trying to import dashboard without creating
datasources first. Currently it causes error 500 with a message

> sqlalchemy.orm.exc.NoResultFound: No row was found for one()

which is difficult to understand.

This commit catches NoResultFound error and returns human readable error
using flash('danger').

Ref: #2992

superset/connectors/sqla/models.py

@@ -42,6 +42,7 @@ from sqlalchemy import (
 )
 from sqlalchemy.exc import CompileError
 from sqlalchemy.orm import backref, relationship
+from sqlalchemy.orm.exc import NoResultFound
 from sqlalchemy.schema import UniqueConstraint
 from sqlalchemy.sql import column, literal_column, table, text
 from sqlalchemy.sql.expression import Label, TextAsFrom
@@ -50,6 +51,7 @@ import sqlparse
 from superset import app, db, security_manager
 from superset.connectors.base.models import BaseColumn, BaseDatasource, BaseMetric
 from superset.db_engine_specs.base import TimestampExpression
+from superset.exceptions import DatabaseNotFound
 from superset.jinja_context import get_template_processor
 from superset.models.annotations import Annotation
 from superset.models.core import Database
@@ -1005,11 +1007,19 @@ class SqlaTable(Model, BaseDatasource):
             )
 
         def lookup_database(table):
-            return (
-                db.session.query(Database)
-                .filter_by(database_name=table.params_dict["database_name"])
-                .one()
-            )
+            try:
+                return (
+                    db.session.query(Database)
+                    .filter_by(database_name=table.params_dict["database_name"])
+                    .one()
+                )
+            except NoResultFound:
+                raise DatabaseNotFound(
+                    _(
+                        "Database '%(name)s' is not found",
+                        name=table.params_dict["database_name"],
+                    )
+                )
 
         return import_datasource.import_datasource(
             db.session, i_datasource, lookup_database, lookup_sqlatable, import_time

superset/exceptions.py

@@ -54,3 +54,7 @@ class SupersetTemplateException(SupersetException):
 
 class SpatialException(SupersetException):
     pass
+
+
+class DatabaseNotFound(SupersetException):
+    status = 400

superset/views/core.py

@@ -64,7 +64,11 @@ from superset import (
 )
 from superset.connectors.connector_registry import ConnectorRegistry
 from superset.connectors.sqla.models import AnnotationDatasource, SqlaTable
-from superset.exceptions import SupersetException, SupersetSecurityException
+from superset.exceptions import (
+    DatabaseNotFound,
+    SupersetException,
+    SupersetSecurityException,
+)
 from superset.forms import CsvToDatabaseForm
 from superset.jinja_context import get_template_processor
 from superset.legacy import update_time_range
@@ -1441,7 +1445,26 @@ class Superset(BaseSupersetView):
         """Overrides the dashboards using json instances from the file."""
         f = request.files.get("file")
         if request.method == "POST" and f:
-            dashboard_import_export.import_dashboards(db.session, f.stream)
+            try:
+                dashboard_import_export.import_dashboards(db.session, f.stream)
+            except DatabaseNotFound as e:
+                flash(
+                    _(
+                        "Cannot import dashboard: %(db_error)s.\n"
+                        "Make sure to create the database before "
+                        "importing the dashboard.",
+                        db_error=e,
+                    ),
+                    "danger",
+                )
+            except Exception:
+                flash(
+                    _(
+                        "An unknown error occurred. "
+                        "Please contact your Superset administrator"
+                    ),
+                    "danger",
+                )
             return redirect("/dashboard/list/")
         return self.render_template("superset/import_dashboards.html")