Improve input checks for pagination params

Signed-off-by: Fredrik Adelöw <freben@gmail.com>

plugins/catalog-backend/src/database/CommonDatabase.ts

@@ -563,17 +563,17 @@ function parsePagination(
       const json = Buffer.from(input.after, 'base64').toString('utf8');
       cursor = JSON.parse(json);
     } catch {
-      throw new InputError('Malformed after cursor');
+      throw new InputError('Malformed after cursor, could not be parsed');
     }
     if (cursor.limit !== undefined) {
       if (!Number.isInteger(cursor.limit)) {
-        throw new InputError('Malformed after cursor');
+        throw new InputError('Malformed after cursor, limit was not an number');
       }
       limit = cursor.limit;
     }
     if (cursor.offset !== undefined) {
       if (!Number.isInteger(cursor.offset)) {
-        throw new InputError('Malformed after cursor');
+        throw new InputError('Malformed after cursor, offset was not a number');
       }
       offset = cursor.offset;
     }

plugins/catalog-backend/src/service/request/parseEntityPaginationParams.test.ts

@@ -19,5 +19,33 @@ import { parseEntityPaginationParams } from './parseEntityPaginationParams';
 describe('parseEntityPaginationParams', () => {
   it('works for the happy path', () => {
     expect(parseEntityPaginationParams({})).toBeUndefined();
+    expect(parseEntityPaginationParams({ limit: '1' })).toEqual({ limit: 1 });
+    expect(parseEntityPaginationParams({ offset: '0' })).toEqual({ offset: 0 });
+    expect(parseEntityPaginationParams({ offset: '2' })).toEqual({ offset: 2 });
+    expect(parseEntityPaginationParams({ after: 'x' })).toEqual({ after: 'x' });
+    expect(
+      parseEntityPaginationParams({ limit: '1', offset: '2', after: 'x' }),
+    ).toEqual({ limit: 1, offset: 2, after: 'x' });
+  });
+
+  it('rejects bad values', () => {
+    expect(() => parseEntityPaginationParams({ limit: '' })).toThrow(
+      'Invalid limit, not an integer',
+    );
+    expect(() => parseEntityPaginationParams({ limit: '0' })).toThrow(
+      'Invalid limit, must be greater than zero',
+    );
+    expect(() => parseEntityPaginationParams({ limit: '-1' })).toThrow(
+      'Invalid limit, must be greater than zero',
+    );
+    expect(() => parseEntityPaginationParams({ offset: '' })).toThrow(
+      'Invalid offset, not an integer',
+    );
+    expect(() => parseEntityPaginationParams({ offset: '-1' })).toThrow(
+      'Invalid offset, must be zero or greater',
+    );
+    expect(() => parseEntityPaginationParams({ after: '' })).toThrow(
+      'Invalid after, must not be empty',
+    );
   });
 });

plugins/catalog-backend/src/service/request/parseEntityPaginationParams.ts

@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+import { InputError } from '@backstage/errors';
 import { EntityPagination } from '../../database';
 import { parseIntegerParam, parseStringParam } from './common';
 
@@ -32,9 +33,19 @@ export function parseEntityPaginationParams(
     return undefined;
   }
 
+  if (offset !== undefined && offset < 0) {
+    throw new InputError(`Invalid offset, must be zero or greater`);
+  }
+  if (limit !== undefined && limit <= 0) {
+    throw new InputError(`Invalid limit, must be greater than zero`);
+  }
+  if (after !== undefined && !after) {
+    throw new InputError(`Invalid after, must not be empty`);
+  }
+
   return {
-    ...(offset ? { offset } : {}),
-    ...(limit ? { limit } : {}),
-    ...(after ? { after } : {}),
+    ...(offset !== undefined ? { offset } : {}),
+    ...(limit !== undefined ? { limit } : {}),
+    ...(after !== undefined ? { after } : {}),
   };
 }