Building frontend activates `moc`

[vporton]

Something is wrong.

I see in the terminal:

$ dfx deploy frontend
...
Building frontend...

and in the same time have 100% (one core) allocated to moc process.

How is compiling with .moc related to the frontend? At least, why does this building takes enormous time?

[ericswanson-dfinity]

In a default project, the frontend has a dependency on the backend. The call may be to moc --print-deps while building the dependencies graph.

    "frontend": {
      "dependencies": [
        "backend"
      ],

[vporton]

But it seems to happen after backend canisters are already compiled! First it produces some backend warnings and only then starts time-consuming Building frontend.... That's weird.

WARN: .mops/[email protected]/src/Principal.mo:80.20-80.32: warning [M0154], field append is deprecated:
`Array.append` copies its arguments and has linear complexity;

WARN: .mops/[email protected]/src/Principal.mo:80.20-80.32: warning [M0154], field append is deprecated:
`Array.append` copies its arguments and has linear complexity;

Executing: cargo build --target wasm32-unknown-unknown --release -p ic_eth --locked
    Finished release [optimized] target(s) in 0.20s
Building frontend...

{
  "canisters": {
    "main": {
      "main": "src/backend/main.mo",
      "type": "motoko",
      "dependencies": [
        "order",
        "payments",
        "personhood",
        "CanDBIndex",
        "NacDBIndex",
        "internet_identity",
        "ic_eth"
      ]
    },
    "order": {
      "main": "src/backend/order.mo",
      "type": "motoko"
    },
    "personhood": {
      "main": "src/backend/personhood.mo",
      "type": "motoko",
      "dependencies": ["ic_eth", "CanDBIndex"]
    },
    "frontend": {
      "frontend": {
        "entrypoint": "src/frontend/src/index.html"
      },
      "dependencies": [
        "personhood"
      ],
      "source": [
        "src/frontend/assets",
        "dist/frontend/"
      ],
      "type": "assets"
    },
    "payments": {
      "main": "src/backend/payments.mo",
      "type": "motoko",
      "dependencies": [
        "pst"
      ]
    },
    "pst": {
      "main": "src/backend/pst.mo",
      "type": "motoko"
    },
    "CanDBIndex": {
      "main": "src/storage/CanDBIndex.mo",
      "type": "motoko",
      "dependencies": ["ic_eth"]
    },
    "NacDBIndex": {
      "main": "src/storage/NacDBIndex.mo",
      "type": "motoko",
      "dependencies": ["ic_eth"]
    },
    "CanDBPartition": {
      "main": "src/storage/CanDBPartition.mo",
      "type": "motoko",
      "dependencies": ["ic_eth"]
    },
    "NacDBPartition": {
      "main": "src/storage/NacDBPartition.mo",
      "type": "motoko",
      "dependencies": ["ic_eth"]
    },
    "ic_eth": {
      "type": "rust",
      "candid": "src/ic_eth/ic_eth.did",
      "package": "ic_eth"
    },
    "internet_identity": {
      "type": "custom",
      "candid": "https://github.com/dfinity/internet-identity/releases/latest/download/internet_identity.did",
      "wasm": "https://github.com/dfinity/internet-identity/releases/latest/download/internet_identity_dev.wasm.gz",
      "shrink": false,
      "remote": {
        "candid": "internet_identity.did",
        "id": {
          "ic": "rdmx6-jaaaa-aaaaa-aaadq-cai"
        }
      }
    }
  },
  "ic_eth": {
    "type": "rust",
    "candid": "src/ic_eth/ic_eth.did",
    "package": "ic_eth"
  },
  "defaults": {
    "build": {
      "args": "-fshared-code --actor-idl .dfx/local/lsp",
      "packtool": "mops sources"
    }
  },
  "output_env_file": ".env",
  "version": 1,
  "networks": {
    "local": {
      "bind": "localhost:8000",
      "type": "ephemeral"
    }
  }
}

[chenyan-dfinity]

Right, there is a bug in the prompt. When it shows Building frontend..., it's actually still building backend. You can reproduce this by adding a syntax error in the backend code. The syntax error will show after Building frontend....