refactor(@angular-devkit/core): assert catch clause variable type before usage

Prepares the `@angular-devkit/core` package for the eventual change of enabling the
TypeScript `useUnknownInCatchVariables` option. This option provides additional
code safety by ensuring that the catch clause variable is the proper type before
attempting to access its properties. Similar changes will be needed in the other
packages in the repository prior to enabling `useUnknownInCatchVariables`.

Author: clydin

packages/angular_devkit/core/node/experimental/jobs/job-registry.ts

@@ -12,18 +12,15 @@ import { JsonValue, experimental as core_experimental, schema } from '../../../s
 export class NodeModuleJobRegistry<
   MinimumArgumentValueT extends JsonValue = JsonValue,
   MinimumInputValueT extends JsonValue = JsonValue,
-  MinimumOutputValueT extends JsonValue = JsonValue
+  MinimumOutputValueT extends JsonValue = JsonValue,
 > implements
-    core_experimental.jobs.Registry<
-      MinimumArgumentValueT,
-      MinimumInputValueT,
-      MinimumOutputValueT
-    > {
+    core_experimental.jobs.Registry<MinimumArgumentValueT, MinimumInputValueT, MinimumOutputValueT>
+{
   protected _resolve(name: string): string | null {
     try {
       return require.resolve(name);
     } catch (e) {
-      if (e.code === 'MODULE_NOT_FOUND') {
+      if ((e as NodeJS.ErrnoException).code === 'MODULE_NOT_FOUND') {
         return null;
       }
       throw e;

packages/angular_devkit/core/node/host.ts

@@ -45,7 +45,7 @@ function loadFSWatcher() {
       // eslint-disable-next-line import/no-extraneous-dependencies
       FSWatcher = require('chokidar').FSWatcher;
     } catch (e) {
-      if (e.code !== 'MODULE_NOT_FOUND') {
+      if ((e as NodeJS.ErrnoException).code !== 'MODULE_NOT_FOUND') {
         throw new Error(
           'As of angular-devkit version 8.0, the "chokidar" package ' +
             'must be installed in order to use watch() features.',

packages/angular_devkit/core/src/json/schema/registry.ts

@@ -528,20 +528,21 @@ export class CoreSchemaRegistry implements SchemaRegistry {
             !Array.isArray((parentSchema as JsonObject).default)
               ? undefined
               : ((parentSchema as JsonObject).default as string[]),
-          async validator(data: JsonValue) {
+          async validator(data: JsonValue): Promise<boolean | string> {
             try {
               const result = await it.self.validate(parentSchema, data);
               // If the schema is sync then false will be returned on validation failure
               if (result) {
-                return result;
+                return result as boolean | string;
               } else if (it.self.errors?.length) {
                 // Validation errors will be present on the Ajv instance when sync
-                return it.self.errors[0].message;
+                return it.self.errors[0].message as string;
               }
             } catch (e) {
+              const validationError = e as { errors?: Error[] };
               // If the schema is async then an error will be thrown on validation failure
-              if (Array.isArray(e.errors) && e.errors.length) {
-                return e.errors[0].message;
+              if (Array.isArray(validationError.errors) && validationError.errors.length) {
+                return validationError.errors[0].message;
               }
             }