feat: add Electric-SQL replication plugin

[Copilot]

Adds replication-electric-sql plugin that syncs PostgreSQL data to RxDB collections via Electric-SQL's shape streaming HTTP API.

Plugin (src/plugins/replication-electric-sql/)

• Pull: Fetches from Electric's /v1/shape endpoint with offset-based checkpointing. Handles must-refetch control messages by retrying from scratch within the pull handler.
• Live: Long-polls Electric with live=true after initial sync, delivering documents directly through pullStream$. Falls back with retry on error.
• Push: Passthrough to user-provided handler — Electric only has a read path, so writes go to the user's own backend API.
• Types, helpers, and RxElectricSQLReplicationState class follow the same patterns as replication-supabase and replication-firestore.

Integration

• Export entry in package.json, generated plugin bridge files in plugins/replication-electric-sql/
• Documentation page in docs-src/docs/replication-electric-sql.md with sidebar entry

Tests (test/replication-electric-sql.test.ts)

20 tests using mock fetch functions (no backend required):

• Helper function unit tests: buildElectricUrl, electricMessageToRxDBDocData, hasMustRefetch
• Pull replication: basic pull, checkpoint tracking, delete operations, must-refetch recovery, custom headers
• Push replication: user-provided push handler passthrough
• Live replication: real-time polling delivers new documents via pull stream
• Error handling: HTTP errors emitted on error$ with recovery
• Instance type: returns correct RxElectricSQLReplicationState

CI

• Added test:replication-electric-sql npm script in package.json
• Added to test-others job in .github/workflows/main.yml alongside other no-backend replication tests (google-drive, microsoft-onedrive)

Usage

import { replicateElectricSQL } from 'rxdb/plugins/replication-electric-sql';

const replication = replicateElectricSQL({
    collection: db.items,
    replicationIdentifier: 'items-electric',
    url: 'http://localhost:3000/v1/shape',
    params: {
        table: 'items',
        where: "status='active'"
    },
    live: true,
    pull: { batchSize: 100 },
    push: {
        async handler(rows) {
            // write to your own backend
            return conflicts;
        }
    }
});

No dependency on @electric-sql/client — communicates with Electric over plain HTTP/JSON using the standard fetch API (or a user-provided fetch function).

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[pubkey]

@copilot add tests

[Copilot]

@copilot add tests

Added comprehensive tests in test/replication-electric-sql.test.ts (20 tests, all passing) in commit 407e123. Tests use mock fetch functions so no backend is needed.

Coverage includes:

• Helper function unit tests (buildElectricUrl, electricMessageToRxDBDocData, hasMustRefetch)
• Pull replication (basic pull, checkpoint tracking, deletes, must-refetch retry, custom headers)
• Push handler passthrough
• Live polling for real-time updates
• Error handling and recovery
• Instance type verification

Also fixed the must-refetch handling in the pull handler to properly retry from scratch within the handler rather than returning an empty result to the replication framework.

[pubkey]

@copilot add to CI

[Copilot]

@copilot add to CI

Added in d1b4e63:

• test:replication-electric-sql npm script in package.json
• CI step in .github/workflows/main.yml under the test-others job, alongside replication-google-drive and replication-microsoft-onedrive (no backend required since tests use mock fetch)