feat(proposals): use selfDescribingAction from governance canister instead of nns-dapp payload

[yhabib]

Motivation

The governance canister now exposes a selfDescribingAction field on proposals via a returnSelfDescribingAction flag in listProposals. This field contains the decoded proposal action data (type name, description, and value) directly in the response. Before, we had to fetch and decode the proposal payload separately through the nns-dapp canister's get_proposal_payload endpoint, which internally used the rs/proposals crate to parse raw Candid binary into JSON via idl2json. Since the governance canister now does this translation itself, the nns-dapp canister endpoint and all the frontend code around it become redundant.

Note that this PR only addresses /frontend; a follow-up will clean up /rs.

Changes

• Added returnSelfDescribingAction: true to both queryProposals and queryProposal API calls.
• Removed queryProposalPayload from the API layer and loadProposalPayload from
  the service layer.
• Removed proposalPayloadsStore and related types.
• Removed getProposalPayload method from NNSDappCanister and its error classes (ProposalPayloadNotFoundError, ProposalPayloadTooLargeError, UnknownProposalPayloadError).
• Deleted NnsProposalProposerPayloadEntry.svelte and ProposalProposerPayloadEntry.svelte components.
• Updated NnsProposalProposerActionsEntry.svelte to render action data from selfDescribingAction.value using a new selfDescribingValueToJson utility.
• Simplified mapProposalType to derive the proposal type label and description directly from selfDescribingAction.typeName and typeDescription.
• Added selfDescribingValueToJson utility that converts the SelfDescribingValue Candid tagged union to a plain JS object, with alphabetical key sorting to match the previous behavior.
• Removed i18n action and nns function label translations that are no longer needed (actions, actions_description, nns_functions, nns_functions_description).

Tests

• Updated tests.

Todos

• Accessibility (a11y) – any impact?
• Changelog – is it needed?

[yhabib]

Blocked by dfinity/snsdemo#582 as we need a new version of the replica with an updated governance canister.

[Copilot]

Pull request overview

This PR updates the frontend proposals flow to rely on the governance canister’s selfDescribingAction (requested via returnSelfDescribingAction: true) instead of fetching/decoding proposal payloads via the nns-dapp canister, removing the now-redundant payload API/store/components and associated i18n labels.

Changes:

• Request selfDescribingAction in queryProposals and queryProposal, and remove the proposal payload fetch path (API/service/canister method/errors/store).
• Render proposer “payload/action” details from selfDescribingAction.value via the new selfDescribingValueToJson utility.
• Remove action / NNS-function i18n label tables and update unit/e2e tests accordingly.

Reviewed changes

Copilot reviewed 27 out of 28 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
frontend/src/lib/api/proposals.api.ts	Adds returnSelfDescribingAction: true; removes queryProposalPayload API.
frontend/src/lib/services/public/proposals.services.ts	Removes loadProposalPayload service logic and related error handling/toasts.
frontend/src/lib/stores/proposals.store.ts	Removes proposalPayloadsStore and related payload types.
frontend/src/lib/utils/proposals.utils.ts	Derives proposal type from selfDescribingAction; adds selfDescribingValueToJson conversion utility.
frontend/src/lib/components/proposal-detail/NnsProposalProposerActionsEntry.svelte	Switches proposer action/payload rendering to selfDescribingAction.value and labels section as “Payload”.
frontend/src/lib/components/proposal-detail/NnsProposal.svelte	Removes proposer payload entry component from the proposal detail page.
frontend/src/lib/components/proposal-detail/ProposalProposerPayloadEntry.svelte	Deleted (payload entry no longer needed).
frontend/src/lib/components/proposal-detail/NnsProposalProposerPayloadEntry.svelte	Deleted (nns-dapp payload fetch UI no longer needed).
frontend/src/lib/canisters/nns-dapp/nns-dapp.canister.ts	Removes getProposalPayload method and related imports.
frontend/src/lib/canisters/nns-dapp/nns-dapp.errors.ts	Removes proposal-payload-specific error classes.
frontend/src/lib/i18n/en.json	Removes proposal-payload-related error strings.
frontend/src/lib/i18n/en.governance.json	Removes actions* and nns_functions* label/description tables.
frontend/src/lib/types/i18n.d.ts	Removes corresponding i18n type definitions for deleted keys.
frontend/src/tests/lib/api/proposals.api.spec.ts	Updates API expectations; removes payload API tests.
frontend/src/tests/lib/services/public/proposals.services.spec.ts	Removes payload service tests and store assertions.
frontend/src/tests/lib/stores/proposals.store.spec.ts	Removes proposalPayloadsStore tests.
frontend/src/tests/lib/canisters/nns-dapp.canister.spec.ts	Removes getProposalPayload method tests and payload error expectations.
frontend/src/tests/lib/utils/proposals.utils.spec.ts	Updates type mapping tests; adds selfDescribingValueToJson unit tests.
frontend/src/tests/lib/components/proposals/NnsProposalCard.spec.ts	Updates card heading expectations to use selfDescribingAction-derived type.
frontend/src/tests/lib/components/proposal-detail/ProjectSystemInfoSection.spec.ts	Updates system info type rendering expectations to use selfDescribingAction.
frontend/src/tests/lib/components/proposal-detail/NnsProposalProposerActionsEntry.spec.ts	Updates proposer actions/payload rendering tests to use selfDescribingAction.value.
frontend/src/tests/lib/components/proposal-detail/NnsProposal.spec.ts	Removes proposer payload entry assertion and payload API mocking.
frontend/src/tests/lib/components/proposal-detail/ProposalProposerPayloadEntry.spec.ts	Deleted (component removed).
frontend/src/tests/lib/components/proposal-detail/NnsProposalProposerPayloadEntry.spec.ts	Deleted (component removed).
frontend/src/tests/lib/services/vote-registration.services.spec.ts	Updates proposal type label expectation (no longer i18n-driven).
frontend/src/tests/mocks/proposal.mock.ts	Adds selfDescribingAction to proposal mock data.
frontend/src/tests/mocks/proposals.store.mock.ts	Adds selfDescribingAction to proposals store mock data.
frontend/src/tests/e2e/proposals.spec.ts	Updates E2E expectation for proposer actions section title (“Payload”).

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.