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A screenshot that you have tested with "Try this API".

This is provably a client error as it happens only post version 7.9.2

Link to the code that reproduces this issue. A link to a public Github Repository or gist with a minimal reproduction.

https://gist.github.com/kirstu/2d343883f04c7f29fc8f065b9f6928e1

A step-by-step description of how to reproduce the issue, based on the linked reproduction.

1. Follow steps in https://cloud.google.com/bigquery/docs/paging-results#iterate_through_client_libraries_results
2. Observe error: "Cannot read properties of undefined (reading 'fields')"

Error is thrown from mergeSchemaWithRows_ function here. Most likely happens because this.metadata.schema is undefined here

Full stack trace

TypeError: Cannot read properties of undefined (reading 'fields')
      at Function.mergeSchemaWithRows_ (node_modules/.pnpm/@google-cloud+bigquery@7.9.2/node_modules/@google-cloud/bigquery/build/src/bigquery.js:305:35)
      at onComplete (node_modules/.pnpm/@google-cloud+bigquery@7.9.2/node_modules/@google-cloud/bigquery/build/src/table.js:972:32)
      at node_modules/.pnpm/@google-cloud+bigquery@7.9.2/node_modules/@google-cloud/bigquery/build/src/table.js:1007:13
      at node_modules/.pnpm/@google-cloud+common@5.0.2/node_modules/@google-cloud/common/build/src/util.js:412:25
      at Util.handleResp (node_modules/.pnpm/@google-cloud+common@5.0.2/node_modules/@google-cloud/common/build/src/util.js:161:9)
      at node_modules/.pnpm/@google-cloud+common@5.0.2/node_modules/@google-cloud/common/build/src/util.js:534:22
      at onResponse (node_modules/.pnpm/retry-request@7.0.2/node_modules/retry-request/index.js:259:7)
      at /Volumes/Dev/pasisalo/Projects/hox/node_modules/.pnpm/teeny-request@9.0.0/node_modules/teeny-request/src/index.ts:320:13

A clear and concise description of what the bug is, and what you expected to happen.

table.getRows should return a response, instead an error is thrown

A clear and concise description WHY you expect this behavior, i.e., was it a recent change, there is documentation that points to this behavior, etc. **

The change introduced in release 7.9.2 is causing the issue. Version prior to 7.9.2 work just as expected. From the linked commit it's pretty obvious why the error happens.