feat(externals): add flag to not throw if externals semver have mismatch

__tests__/server/utils/onModuleLoad.spec.jsx

@@ -253,6 +253,20 @@ describe('onModuleLoad', () => {
     expect(() => onModuleLoad({ module: { [CONFIGURATION_KEY]: configuration, [META_DATA_KEY]: { version: '1.0.11' } }, moduleName: 'my-awesome-module' })).toThrowErrorMatchingSnapshot();
   });
 
+  it('logs a warning if the root module provides an incompatible version of a required external and ONE_DANGEROUSLY_ACCEPT_BREAKING_EXTERNALS is set to true', () => {
+    process.env.ONE_DANGEROUSLY_ACCEPT_BREAKING_EXTERNALS = true;
+    RootModule[CONFIGURATION_KEY].providedExternals = {
+      'dep-a': { version: '2.1.0', module: () => 0 },
+    };
+    const configuration = {
+      requiredExternals: {
+        'dep-a': '^2.1.1',
+      },
+    };
+    expect(() => onModuleLoad({ module: { [CONFIGURATION_KEY]: configuration, [META_DATA_KEY]: { version: '1.0.10' } }, moduleName: 'my-awesome-module' })).not.toThrow();
+    expect(consoleWarnSpy).toHaveBeenCalledTimes(1);
+  });
+
   it('keeps track of the externals a module is using', () => {
     RootModule[CONFIGURATION_KEY] = {
       providedExternals: {

docs/api/server/Environment-Variables.md

@@ -33,6 +33,7 @@ One App can be configured via Environment Variables:
   * [`NODE_ENV`](#node_env) ⚠️
   * [`ONE_CLIENT_ROOT_MODULE_NAME`](#one_client_root_module_name) ⚠️
   * [`ONE_CONFIG_ENV`](#one_config_env) ⚠️
+  * [`ONE_DANGEROUSLY_ACCEPT_BREAKING_EXTERNALS`](#ONE_DANGEROUSLY_ACCEPT_BREAKING_EXTERNALS)
 * Server Settings
   * [`HOLOCRON_SERVER_MAX_MODULES_RETRY`](#holocron_server_max_modules_retry)
   * [`HOLOCRON_SERVER_MAX_SIM_MODULES_FETCH`](#holocron_server_max_sim_modules_fetch)
@@ -510,6 +511,31 @@ ONE_CONFIG_ENV=staging
 ONE_CONFIG_ENV=undefined
 ```
 
+## `ONE_DANGEROUSLY_ACCEPT_BREAKING_EXTERNALS`
+
+**Runs In**
+* ✅ Production
+* ✅ Development
+
+If set to `true`, one-app will not throw an error when externals provided by the root module and externals required by child modules have conflicting semver ranges.
+This flag is meant to ease the transition to newer versions of externals. It should not be kept on for long as mismatching versions of packages can cause unexpected issues.
+
+**Shape**
+```bash
+ONE_DANGEROUSLY_ACCEPT_BREAKING_EXTERNALS=true
+```
+
+**Example**
+```bash
+ONE_DANGEROUSLY_ACCEPT_BREAKING_EXTERNALS=true
+```
+
+**Default Value**
+```bash
+ONE_DANGEROUSLY_ACCEPT_BREAKING_EXTERNALS=undefined
+```
+
+
 ## `ONE_ENABLE_POST_TO_MODULE_ROUTES`
 
 **Runs In**

src/server/utils/onModuleLoad.js

@@ -147,7 +147,12 @@ export default function onModuleLoad({
       if (!providedExternal) {
         messages.push(`External '${externalName}' is required by ${moduleName}, but is not provided by the root module`);
       } else if (!semver.satisfies(providedExternal.version, requestedExternalVersion)) {
-        messages.push(`${externalName}@${requestedExternalVersion} is required by ${moduleName}, but the root module provides ${providedExternal.version}`);
+        const failedExternalMessage = `${externalName}@${requestedExternalVersion} is required by ${moduleName}, but the root module provides ${providedExternal.version}`;
+        if (process.env.ONE_DANGEROUSLY_ACCEPT_BREAKING_EXTERNALS) {
+          console.warn(failedExternalMessage);
+        } else {
+          messages.push(failedExternalMessage);
+        }
       }
     });