A decorator that fails to resolve reports its error twice

.bumpy/decorator-error-once.md

@@ -0,0 +1,5 @@
+---
+"varlock": patch
+---
+
+An error from a decorator's value (for example `@required=forEnv(prod)` when the current environment is not set) is reported once instead of twice

packages/varlock/src/env-graph/lib/decorators.ts

@@ -210,9 +210,11 @@ export abstract class DecoratorInstance {
 
   resolvedValue?: any;
   isResolved = false;
+  /** set when resolving threw, so a later call does not run the resolver and record the same error again */
+  private resolveFailed = false;
 
   async resolve() {
-    if (this.isResolved) return this.resolvedValue;
+    if (this.isResolved || this.resolveFailed) return this.resolvedValue;
 
     await this.process();
     // decorators that skip value-resolver creation (see process()) have nothing to resolve
@@ -229,6 +231,7 @@ export abstract class DecoratorInstance {
       this.resolvedValue = await this.decValueResolver.resolve();
     } catch (err) {
       this._errors.push(err as any);
+      this.resolveFailed = true;
       return;
     }
 

packages/varlock/src/env-graph/test/decorator-error-once.test.ts

@@ -0,0 +1,24 @@
+import { describe, it, expect } from 'vitest';
+import outdent from 'outdent';
+import { EnvGraph } from '../index';
+import { DotEnvFileDataSource } from '../lib/data-source';
+
+describe('a decorator whose resolver throws', () => {
+  it('reports the error once', async () => {
+    const g = new EnvGraph();
+    await g.setRootDataSource(new DotEnvFileDataSource('.env.schema', {
+      overrideContents: outdent`
+        # @currentEnv=$APP_ENV
+        # @defaultRequired=false
+        # ---
+        # @type=enum(dev, prod)
+        APP_ENV=
+        # @required=forEnv(prod)
+        API_URL=
+      `,
+    }));
+    await g.finishLoad();
+    await g.resolveEnvValues();
+    expect(g.configSchema.API_URL.errors.map((e) => e.message)).toEqual(['forEnv(): current environment is not set']);
+  });
+});