feat: Add sql.js fallback for sqlite in wasm

.github/workflows/sqlite-wasm.yml

@@ -0,0 +1,37 @@
+name: Tests WASM
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    types: [opened, synchronize, reopened, auto_merge_enabled]
+
+# Allow parallel jobs on `main`, so that each commit is tested. For PRs, run only the latest commit.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    name: Node.js ${{ matrix.node }}
+
+    strategy:
+      fail-fast: true
+      matrix:
+        node: [18]
+
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: ${{ matrix.node }}
+          cache: 'npm'
+
+      - run: npm ci
+      # Remove better-sqlite3 to force switching to sql.js
+      - run: npm install sql.js && rm -rf node_modules/better-sqlite3/
+      - run: npm test -w sqlite -- --maxWorkers=1
+        env:
+          FORCE_COLOR: true

sqlite/lib/SQLiteService.js

@@ -1,6 +1,12 @@
 const { SQLService } = require('@cap-js/db-service')
 const cds = require('@sap/cds/lib')
-const sqlite = require('better-sqlite3')
+let sqlite
+try {
+  sqlite = require('better-sqlite3')
+} catch (err) {
+  // When failing to load better-sqlite3 it fallsback to sql.js (wasm version of sqlite)
+  sqlite = require('./sql.js.js')
+}
 const $session = Symbol('dbc.session')
 const convStrm = require('stream/consumers')
 const { Readable } = require('stream')
@@ -20,9 +26,10 @@ class SQLiteService extends SQLService {
   get factory() {
     return {
       options: { max: 1, ...this.options.pool },
-      create: tenant => {
+      create: async tenant => {
         const database = this.url4(tenant)
         const dbc = new sqlite(database)
+        await dbc.ready
 
         const deterministic = { deterministic: true }
         dbc.function('session_context', key => dbc[$session][key])
@@ -224,7 +231,7 @@ class SQLiteService extends SQLService {
       // int64 is stored as native int64 for best comparison
       // Reading int64 as string to not loose precision
       Int64: expr => `CAST(${expr} as TEXT)`,
-      
+
       // Reading decimal as string to not loose precision
       Decimal: expr => `CAST(${expr} as TEXT)`,
 

sqlite/lib/sql.js.js

@@ -0,0 +1,84 @@
+const initSqlJs = require('sql.js');
+
+const init = initSqlJs({})
+
+class WasmSqlite {
+  constructor(database) {
+    // TODO: load / store database file contents
+    this.ready = init
+      .then(SQL => { this.db = new SQL.Database() })
+
+    this.memory = true
+    this.gc = new FinalizationRegistry(stmt => { stmt.free() })
+  }
+
+  prepare(sql) {
+    const stmt = this.db.prepare(sql)
+    const ret = {
+      run: (params) => {
+        try {
+          stmt.bind(params)
+          stmt.step()
+          return { changes: this.db.getRowsModified(stmt) }
+        } catch (err) {
+          if (err.message.indexOf('NOT NULL constraint failed:') === 0) {
+            err.code = 'SQLITE_CONSTRAINT_NOTNULL'
+          }
+          throw err
+        }
+      },
+      get: (params) => {
+        const columns = stmt.getColumnNames()
+        stmt.bind(params)
+        stmt.step()
+        const row = stmt.get()
+        const ret = {}
+        for (let i = 0; i < columns.length; i++) {
+          ret[columns[i]] = row[i]
+        }
+        return ret
+      },
+      all: (params) => {
+        const columns = stmt.getColumnNames()
+        const ret = []
+        stmt.bind(params)
+        while (stmt.step()) {
+          const row = stmt.get()
+          const obj = {}
+          for (let i = 0; i < columns.length; i++) {
+            obj[columns[i]] = row[i]
+          }
+          ret.push(obj)
+        }
+        return ret
+      }
+    }
+    this.gc.register(ret, stmt)
+    return ret
+  }
+
+  exec(sql) {
+    try {
+      const { columns, values } = this.db.exec(sql)
+      return !Array.isArray(values) ? values : values.map(val => {
+        const ret = {}
+        for (let i = 0; i < columns.length; i++) {
+          ret[columns[i]] = val[i]
+        }
+        return ret
+      })
+    } catch (err) {
+      // REVISIT: address transaction errors
+      if (sql === 'BEGIN' || sql === 'ROLLBACK') { return }
+      throw err
+    }
+  }
+
+  function(name, config, func) {
+    this.db.create_function(name, func || config)
+  }
+
+  close() { this.db.close() }
+}
+
+module.exports = WasmSqlite

sqlite/package.json

@@ -33,6 +33,9 @@
     "@cap-js/db-service": "^1.7.0",
     "better-sqlite3": "^9.3.0"
   },
+  "optionalDependencies": {
+    "sql.js": "^1.10.3"
+  },
   "peerDependencies": {
     "@sap/cds": ">=7.6"
   },