feat: add support for skipped steps in client (#601)

# Add support for skipped steps in the client

This PR adds support for handling skipped steps in the PgFlow client. Skipped steps can occur in three scenarios:
- When a step's condition evaluates to false (`condition_unmet`)
- When a dependency was skipped, causing cascading skips (`dependency_skipped`)
- When a handler fails during evaluation (`handler_failed`)

The implementation:
- Adds a new `Skipped` status to the `FlowStepStatus` enum
- Introduces a `SkipReason` type to track why a step was skipped
- Extends `FlowStep` with `skipped_at` and `skip_reason` properties
- Updates event handling to process skipped step events
- Treats skipped as a terminal state (like completed and failed)
- Adds support for `waitForStatus(FlowStepStatus.Skipped)`

Comprehensive tests verify the client correctly:
- Handles skipped step state from database snapshots
- Processes skipped broadcast events
- Maintains skipped as a terminal state
- Resolves `waitForStatus(Skipped)` correctly
- Handles all skip reasons appropriately

Author: jumski

pkgs/client/__tests__/e2e/skipped-steps.test.ts

@@ -0,0 +1,205 @@
+import { describe, it, expect } from 'vitest';
+import { withPgNoTransaction } from '../helpers/db.js';
+import { createTestSupabaseClient } from '../helpers/setup.js';
+import { createTestFlow } from '../helpers/fixtures.js';
+import { grantMinimalPgflowPermissions } from '../helpers/permissions.js';
+import { PgflowClient } from '../../src/lib/PgflowClient.js';
+import { FlowStepStatus } from '../../src/lib/types.js';
+import { cleanupFlow } from '../helpers/cleanup.js';
+import { createEventTracker } from '../helpers/test-utils.js';
+import { skipStep } from '../helpers/skip-step.js';
+
+/**
+ * Tests for skipped step event handling in the client.
+ *
+ * Skipped steps can occur when:
+ * - A step's condition evaluates to false (condition_unmet)
+ * - A dependency was skipped, causing cascading skips (dependency_skipped)
+ * - A handler fails during evaluation (handler_failed)
+ *
+ * These tests verify the client correctly:
+ * - Receives and processes skipped broadcast events
+ * - Updates step state with skipped_at and skip_reason
+ * - Treats skipped as a terminal state
+ * - Handles waitForStatus(Skipped) correctly
+ */
+describe('Skipped Step Handling', () => {
+  it(
+    'client handles skipped step state from database snapshot',
+    withPgNoTransaction(async (sql) => {
+      // This test verifies the client correctly handles skipped step state
+      // when fetched from the database (e.g., on reconnect or late join)
+
+      const testFlow = createTestFlow('skip_snap');
+      await cleanupFlow(sql, testFlow.slug);
+      await grantMinimalPgflowPermissions(sql);
+
+      await sql`SELECT pgflow.create_flow(${testFlow.slug})`;
+      await sql`SELECT pgflow.add_step(${testFlow.slug}, 'will_skip_step')`;
+
+      const supabaseClient = createTestSupabaseClient();
+      const pgflowClient = new PgflowClient(supabaseClient, {
+        realtimeStabilizationDelayMs: 1000,
+      });
+
+      // Start the flow
+      const run = await pgflowClient.startFlow(testFlow.slug, { test: 'data' });
+      const step = run.step('will_skip_step');
+
+      // Verify initial state is Started (root step)
+      expect(step.status).toBe(FlowStepStatus.Started);
+
+      // Directly call pgflow.skip_step to simulate the step being skipped
+      // This mimics what would happen when a condition evaluates to false
+      await skipStep(sql, run.run_id, 'will_skip_step', 'condition_unmet');
+
+      // Wait for the skipped event to be received
+      await step.waitForStatus(FlowStepStatus.Skipped, { timeoutMs: 10000 });
+
+      // Verify skipped state
+      expect(step.status).toBe(FlowStepStatus.Skipped);
+      expect(step.skipped_at).toBeInstanceOf(Date);
+      expect(step.skip_reason).toBe('condition_unmet');
+
+      // Verify output is null for skipped steps (per design decision Q1)
+      expect(step.output).toBeNull();
+
+      await supabaseClient.removeAllChannels();
+    }),
+    { timeout: 15000 }
+  );
+
+  it(
+    'receives skipped broadcast event and updates step state',
+    withPgNoTransaction(async (sql) => {
+      // This test verifies the client receives and processes skipped events
+      // broadcast via Supabase realtime
+
+      const testFlow = createTestFlow('skip_broadcast');
+      await cleanupFlow(sql, testFlow.slug);
+      await grantMinimalPgflowPermissions(sql);
+
+      await sql`SELECT pgflow.create_flow(${testFlow.slug})`;
+      await sql`SELECT pgflow.add_step(${testFlow.slug}, 'skipped_step')`;
+
+      const supabaseClient = createTestSupabaseClient();
+      const pgflowClient = new PgflowClient(supabaseClient, {
+        realtimeStabilizationDelayMs: 1000,
+      });
+
+      const run = await pgflowClient.startFlow(testFlow.slug, { test: 'data' });
+      const step = run.step('skipped_step');
+
+      // Set up event tracking BEFORE the skip happens
+      const tracker = createEventTracker();
+      step.on('*', tracker.callback);
+
+      // Skip the step
+      await skipStep(sql, run.run_id, 'skipped_step', 'handler_failed');
+
+      // Wait for the skipped status
+      await step.waitForStatus(FlowStepStatus.Skipped, { timeoutMs: 10000 });
+
+      // Verify we received the skipped event
+      expect(tracker).toHaveReceivedEvent('step:skipped');
+      expect(tracker).toHaveReceivedEvent('step:skipped', {
+        run_id: run.run_id,
+        step_slug: 'skipped_step',
+        status: FlowStepStatus.Skipped,
+        skip_reason: 'handler_failed',
+      });
+
+      // Verify step state
+      expect(step.status).toBe(FlowStepStatus.Skipped);
+      expect(step.skip_reason).toBe('handler_failed');
+
+      await supabaseClient.removeAllChannels();
+    }),
+    { timeout: 15000 }
+  );
+
+  it(
+    'waitForStatus(Skipped) resolves when step is skipped',
+    withPgNoTransaction(async (sql) => {
+      // Verify waitForStatus works correctly with Skipped status
+
+      const testFlow = createTestFlow('wait_skip');
+      await cleanupFlow(sql, testFlow.slug);
+      await grantMinimalPgflowPermissions(sql);
+
+      await sql`SELECT pgflow.create_flow(${testFlow.slug})`;
+      await sql`SELECT pgflow.add_step(${testFlow.slug}, 'wait_step')`;
+
+      const supabaseClient = createTestSupabaseClient();
+      const pgflowClient = new PgflowClient(supabaseClient, {
+        realtimeStabilizationDelayMs: 1000,
+      });
+
+      const run = await pgflowClient.startFlow(testFlow.slug, { test: 'data' });
+      const step = run.step('wait_step');
+
+      // Start waiting for skipped BEFORE the skip happens
+      const waitPromise = step.waitForStatus(FlowStepStatus.Skipped, {
+        timeoutMs: 10000,
+      });
+
+      // Skip the step after a small delay
+      setTimeout(async () => {
+        await skipStep(sql, run.run_id, 'wait_step', 'condition_unmet');
+      }, 100);
+
+      // Wait should resolve with the step
+      const result = await waitPromise;
+      expect(result).toBe(step);
+      expect(result.status).toBe(FlowStepStatus.Skipped);
+      expect(result.skip_reason).toBe('condition_unmet');
+
+      await supabaseClient.removeAllChannels();
+    }),
+    { timeout: 15000 }
+  );
+
+  it(
+    'handles all skip reasons correctly',
+    withPgNoTransaction(async (sql) => {
+      // Verify all three skip reasons are handled correctly
+
+      const skipReasons = [
+        'condition_unmet',
+        'handler_failed',
+        'dependency_skipped',
+      ] as const;
+
+      for (const skipReason of skipReasons) {
+        const testFlow = createTestFlow(`skip_${skipReason}`);
+        await cleanupFlow(sql, testFlow.slug);
+        await grantMinimalPgflowPermissions(sql);
+
+        await sql`SELECT pgflow.create_flow(${testFlow.slug})`;
+        await sql`SELECT pgflow.add_step(${testFlow.slug}, 'reason_step')`;
+
+        const supabaseClient = createTestSupabaseClient();
+        const pgflowClient = new PgflowClient(supabaseClient, {
+          realtimeStabilizationDelayMs: 1000,
+        });
+
+        const run = await pgflowClient.startFlow(testFlow.slug, {
+          test: 'data',
+        });
+        const step = run.step('reason_step');
+
+        // Skip with specific reason
+        await skipStep(sql, run.run_id, 'reason_step', skipReason);
+
+        await step.waitForStatus(FlowStepStatus.Skipped, { timeoutMs: 10000 });
+
+        // Verify the skip reason was captured correctly
+        expect(step.status).toBe(FlowStepStatus.Skipped);
+        expect(step.skip_reason).toBe(skipReason);
+
+        await supabaseClient.removeAllChannels();
+      }
+    }),
+    { timeout: 45000 }
+  );
+});

pkgs/client/__tests__/e2e/supabase-setup.test.ts

@@ -7,6 +7,7 @@ import type {
   BroadcastStepStartedEvent,
   BroadcastStepCompletedEvent,
   BroadcastStepFailedEvent,
+  BroadcastStepSkippedEvent,
 } from '../../src/lib/types';
 
 /**
@@ -98,3 +99,17 @@ export function createStepFailedEvent(
     ...overrides,
   };
 }
+
+export function createStepSkippedEvent(
+  overrides: Partial<BroadcastStepSkippedEvent> = {}
+): BroadcastStepSkippedEvent {
+  return {
+    event_type: 'step:skipped',
+    run_id: '123e4567-e89b-12d3-a456-426614174000',
+    step_slug: 'test-step',
+    status: FlowStepStatus.Skipped,
+    skipped_at: new Date().toISOString(),
+    skip_reason: 'condition_unmet',
+    ...overrides,
+  };
+}

pkgs/client/__tests__/helpers/event-factories.ts

@@ -4,10 +4,12 @@ export function createTestFlow(flowSlug?: string) {
   const uniqueSuffix = `${Date.now()}_${Math.random()
     .toString(36)
     .substr(2, 5)}`;
+
+  const maxBaseLength = 48 - uniqueSuffix.length - 1;
+  const baseSlug = flowSlug ? flowSlug.slice(0, maxBaseLength) : 'test_flow';
+
   return {
-    slug: flowSlug
-      ? `${flowSlug}_${uniqueSuffix}`
-      : `test_flow_${uniqueSuffix}`,
+    slug: `${baseSlug}_${uniqueSuffix}`,
     options: {},
   };
 }

pkgs/client/__tests__/helpers/fixtures.ts

@@ -0,0 +1,19 @@
+import type postgres from 'postgres';
+
+/**
+ * Skip a step using the internal _cascade_force_skip_steps function.
+ * This is a test helper that wraps the internal function.
+ * If pgflow.skip_step() is exposed publicly later, swap implementation here.
+ */
+export async function skipStep(
+  sql: postgres.Sql,
+  runId: string,
+  stepSlug: string,
+  skipReason: 'condition_unmet' | 'handler_failed' | 'dependency_skipped'
+): Promise<void> {
+  await sql`SELECT pgflow._cascade_force_skip_steps(
+    ${runId}::uuid,
+    ${stepSlug}::text,
+    ${skipReason}::text
+  )`;
+}