opt out of assembly validation by default

packages/@jsii/kernel/src/kernel.ts

@@ -43,6 +43,10 @@ export class Kernel {
    * Set to true for timing data to be emitted.
    */
   public debugTimingEnabled = false;
+  /**
+   * Set to true to validate assemblies upon loading (slow).
+   */
+  public validateAssemblies = false;
 
   readonly #assemblies = new Map<string, Assembly>();
   readonly #objects = new ObjectTable(this.#typeInfoForFqn.bind(this));
@@ -151,7 +155,7 @@ export class Kernel {
     let assmSpec: spec.Assembly;
     try {
       assmSpec = this.#debugTime(
-        () => spec.loadAssemblyFromPath(packageDir),
+        () => spec.loadAssemblyFromPath(packageDir, this.validateAssemblies),
         `loadAssemblyFromPath(${packageDir})`,
       );
     } catch (e: any) {

packages/@jsii/runtime/lib/host.ts

@@ -20,10 +20,12 @@ export class KernelHost {
       debug?: boolean;
       debugTiming?: boolean;
       noStack?: boolean;
+      validateAssemblies?: boolean;
     } = {},
   ) {
     this.kernel.traceEnabled = opts.debug ?? false;
     this.kernel.debugTimingEnabled = opts.debugTiming ?? false;
+    this.kernel.validateAssemblies = opts.validateAssemblies ?? false;
   }
 
   public run() {

packages/@jsii/runtime/lib/program.ts

@@ -9,6 +9,7 @@ const version = packageInfo.version;
 const noStack = !!process.env.JSII_NOSTACK;
 const debug = !!process.env.JSII_DEBUG;
 const debugTiming = !!process.env.JSII_DEBUG_TIMING;
+const validateAssemblies = !!process.env.JSII_VALIDATE_ASSEMBLIES;
 
 // This assumes FD#3 is opened for reading and writing. This is normally
 // performed by`bin/jsii-runtime.js`, and we will not be verifying this once
@@ -25,7 +26,12 @@ const stdio = new SyncStdio({
 });
 
 const inout = new InputOutput(stdio);
-const host = new KernelHost(inout, { debug, noStack, debugTiming });
+const host = new KernelHost(inout, {
+  debug,
+  noStack,
+  debugTiming,
+  validateAssemblies,
+});
 
 host.once('exit', process.exit.bind(process));