What does `dfx build` do for remote canisters?

Developers Motoko
1

What does dfx build do for remote canisters? It thinks more than 2 sec and seems to have done nothing.

$ time dfx build --no-deps --network local nns-cycles-minting
WARN: .did file for canister 'bootstrapper_data' does not exist.
Finished building canisters.

real	0m2.191s
user	0m0.227s
sys	0m0.043s
porton@victor:~/Projects/icp-package-manager$ find -name nns-cycles-minting\*
./src/declarations/nns-cycles-minting
./src/declarations/nns-cycles-minting/nns-cycles-minting.did.d.ts
./src/declarations/nns-cycles-minting/nns-cycles-minting.did.js
./src/declarations/nns-cycles-minting/nns-cycles-minting.did
./candid/nns-cycles-minting.did

    "nns-cycles-minting": {
      "build": "",
      "candid": "candid/nns-cycles-minting.did",
      "remote": {
        "id": {
          "ic": "rkp4c-7iaaa-aaaaa-aaaca-cai",
          "local": "rkp4c-7iaaa-aaaaa-aaaca-cai"
        }
      },
      "type": "custom",
      "wasm": ""
    },
2

It should do nothing besides maybe copying a few files around. It’s likely that if you find for the canister id then you may find a file that has changed. I remember that not copying the .did file caused a bug a while back.

3

I need to know for sure whether it really does nothing. But it spends more 2 sec thinking.

Apparently, I need to study the sources to know.