A Question about relative clause

Question

Today I encountered a sentence:

"At night, we would lie on the porch in the sleeping bags my grandmother had bought, drink cocoa, and listen to the chorus of crickets"

Let take a look at the first part of this sentence:

"we would lie on the porch in the sleeping bags my grandmother had bought"

We can re-write without any change of meaning:

"we would lie on the porch in the sleeping bags which my grandmother had bought"

But I believe that the information "my grandmother had bought" is just additional information so it should be non-defining clause. I think this sentence should be written like this:

"we would lie on the porch in the sleeping bags, which my grandmother had bought"

Then I place this part in the first sentence then the sentence look weird to me:

"At night, we would lie on the porch in the sleeping bags, which my grandmother had bought, drink cocoa, and listen to the chorus of crickets"

Could someone please explain which part of this process is wrong.

Answer 1

The 'rules' about punctuation are not so much rules as guidelines. The purpose of punctuation is to help people to understand the structure of a sentence: if the sentence is clear and understandable, it's correctly punctuated whatever the 'rules' say.

You say that which my grandmother had bought is not defining: I am not convinced. Agreed, it's not particularly important, but it is grammatically necessary for the sentence. Here is the sentence without that clause:

At night, we would lie on the porch in the sleeping bags, drink cocoa, and listen to the chorus of crickets

The sentence mentions the sleeping bags, but (assuming that they were not mentioned in a previous sentence) the reader does not know which sleeping bags you are talking about. What you need is a defining relative clause to specify which sleeping bags you are talking about.

At night, we would lie on the porch in the sleeping bags which my grandmother had bought, drink cocoa, and listen to the chorus of crickets

Note that, if the definite article the were missing, we would not be talking about specific sleeping bags. The relative clause would then no longer be necessary and so the relative clause, if used, would not be defining.

At night, we would lie on the porch in sleeping bags, drink cocoa, and listen to the chorus of crickets

At night, we would lie on the porch in sleeping bags, which my grandmother had bought, drink cocoa, and listen to the chorus of crickets

Note that the initial sentence also contains a relative clause: there is an invisible relative pronoun that after blankets. It is often omitted if the structure of the sentence is clear without it.

Note also that bought means purchased. If you want the past of bring, it's brought.