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Fix apache#375: Capture plugin properties at validation time to eliminate timing mismatch
Maven 4 automatically injects --module-version into compiler arguments during execution, but cache validation happens before execution. This creates a timing mismatch that causes cache invalidation. This fix captures properties at validation time for ALL builds, ensuring consistent reading at the same lifecycle point. Changes: - Modified CacheResult to store validation-time mojo events - Added captureValidationTimeProperties() method to BuildCacheMojosExecutionStrategy - Modified execute() to capture properties after findCachedBuild() - Modified save() to use validation-time events instead of execution-time events - Added comprehensive integration tests (Maven4Jpms, ExplicitModuleVersion, NonJpms, MultiModule) - Added implementation documentation This approach eliminates the need for ignorePattern configuration and fixes the root cause rather than treating the symptom. Alternative to PR apache#391
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‎IMPLEMENTATION_PLAN.md‎

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<!--
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Licensed to the Apache Software Foundation (ASF) under one
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or more contributor license agreements. See the NOTICE file
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distributed with this work for additional information
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regarding copyright ownership. The ASF licenses this file
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to you under the Apache License, Version 2.0 (the
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"License"); you may not use this file except in compliance
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with the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing,
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software distributed under the License is distributed on an
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"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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KIND, either express or implied. See the License for the
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specific language governing permissions and limitations
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under the License.
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-->
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# Implementation Plan: Fix #375 - Validation-Time Property Capture
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## Problem
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Maven 4 automatically injects `--module-version ${project.version}` into compiler arguments during execution, but this happens AFTER the cache validation phase. This creates a timing mismatch:
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- **First build**: Properties captured during execution (WITH injection)
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- **Second build**: Properties captured during validation (WITHOUT injection yet)
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- **Result**: Cache invalidation due to parameter mismatch
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## Root Cause
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Properties are currently captured at different lifecycle points:
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- **Validation phase**: Uses `getConfiguredMojo()` to read properties (no injection yet)
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- **Execution phase**: Maven injects properties before `beforeMojoExecution()` fires
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- **Storage phase**: Reads from execution-time events (possibly with injection)
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## Solution
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Capture properties at **validation time** for ALL builds (not just when cache is found). This ensures consistent reading at the same lifecycle point.
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### Key Changes
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#### 1. Modified CacheResult.java
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- Added `validationTimeEvents` field to store mojo events captured during validation
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- Added overloaded factory methods to accept validation-time events
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- Added `getValidationTimeEvents()` getter
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#### 2. Modify BuildCacheMojosExecutionStrategy.java
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After calling `findCachedBuild()`, capture validation-time properties for all mojos:
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```java
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// After line 133: result = cacheController.findCachedBuild(...)
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Map<String, MojoExecutionEvent> validationTimeEvents = captureValidationTimeProperties(
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session, project, mojoExecutions
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);
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// Store in result using CacheResult.rebuilded() or new factory methods
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```
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Add method:
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```java
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private Map<String, MojoExecutionEvent> captureValidationTimeProperties(
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MavenSession session, MavenProject project, List<MojoExecution> mojoExecutions
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) {
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Map<String, MojoExecutionEvent> events = new HashMap<>();
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for (MojoExecution mojoExecution : mojoExecutions) {
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try {
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mojoExecutionScope.enter();
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mojoExecutionScope.seed(MavenProject.class, project);
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mojoExecutionScope.seed(MojoExecution.class, mojoExecution);
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Mojo mojo = mavenPluginManager.getConfiguredMojo(Mojo.class, session, mojoExecution);
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MojoExecutionEvent event = new MojoExecutionEvent(session, project, mojoExecution, mojo);
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events.put(mojoExecutionKey(mojoExecution), event);
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mavenPluginManager.releaseMojo(mojo, mojoExecution);
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} catch (Exception e) {
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LOGGER.warn("Cannot capture validation-time properties for {}: {}",
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mojoExecution.getGoal(), e.getMessage());
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} finally {
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mojoExecutionScope.exit();
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}
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}
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return events;
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}
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```
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#### 3. Modify BuildCacheMojosExecutionStrategy.execute()
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Pass validation-time events to save():
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```java
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// Line 167: Change from:
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cacheController.save(result, mojoExecutions, executionEvents);
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// To:
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Map<String, MojoExecutionEvent> propertyEvents = result.getValidationTimeEvents() != null
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? result.getValidationTimeEvents()
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: executionEvents;
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cacheController.save(result, mojoExecutions, propertyEvents);
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```
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### Why This Works
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1. **First Build** (no cache):
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- `findCachedBuild()` returns empty result
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- Capture validation-time properties
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- Mojos execute (Maven 4 may inject properties)
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- `save()` uses validation-time properties (NO injection)
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2. **Second Build** (cache found):
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- `findCachedBuild()` validates using validation-time properties (NO injection)
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- Capture validation-time properties
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- Compare to stored values (BOTH without injection)
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- **Match!** Cache restored
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### Benefits
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- ✅ Eliminates timing mismatch
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- ✅ No need for `ignorePattern` workaround
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- ✅ Consistent property reading for all builds
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- ✅ Solves root cause instead of treating symptoms
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- ✅ No configuration required
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- ✅ Works for any Maven 4 auto-injected properties
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### Testing
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Will create integration tests for:
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1. JPMS module without explicit moduleVersion (Maven 4 auto-injects)
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2. JPMS module with empty moduleVersion
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3. JPMS module with null moduleVersion
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4. JPMS module with explicit moduleVersion
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All tests should show cache restoration on second build WITHOUT needing `ignorePattern`.
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## Comparison with PR #391
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**PR #391 (ignorePattern approach)**:
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- Treats symptom: filters out mismatched values
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- Requires configuration
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- Pattern-based (fragile, version-format dependent)
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- Works around the timing problem
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**This PR (validation-time capture)**:
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- Fixes root cause: eliminates timing mismatch
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- No configuration needed
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- Format-agnostic
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- Solves the timing problem
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## Implementation Status
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- [x] Design solution
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- [x] Modify CacheResult.java
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- [ ] Modify BuildCacheMojosExecutionStrategy.java (captureValidationTimeProperties)
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- [ ] Modify BuildCacheMojosExecutionStrategy.execute() (pass validation events to save)
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- [ ] Run existing tests
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- [ ] Create integration tests
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- [ ] Create PR

‎PR_DESCRIPTION.md‎

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<!--
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Licensed to the Apache Software Foundation (ASF) under one
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or more contributor license agreements. See the NOTICE file
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distributed with this work for additional information
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regarding copyright ownership. The ASF licenses this file
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to you under the Apache License, Version 2.0 (the
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"License"); you may not use this file except in compliance
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with the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing,
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software distributed under the License is distributed on an
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"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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KIND, either express or implied. See the License for the
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specific language governing permissions and limitations
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under the License.
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-->
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# Fix #375: Capture plugin properties at validation time to eliminate timing mismatch
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## Problem
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Maven 4 automatically injects `--module-version ${project.version}` into compiler arguments **during execution**, but the build cache validates properties **before execution**. This creates a timing mismatch that causes cache invalidation:
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- **First build**: No cache exists → properties captured during/after execution (WITH Maven 4 injection)
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- **Second build**: Cache exists → properties captured during validation (WITHOUT injection yet) → mismatch → cache invalidated
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## Root Cause Analysis
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The cache extension currently reads plugin properties at **different lifecycle points** for different builds:
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```
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First Build Timeline:
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1. findCachedBuild() → no cache found
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2. Mojos execute → Maven 4 injects --module-version
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3. beforeMojoExecution() fires → captures properties WITH injection
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4. save() stores properties from execution events
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Second Build Timeline:
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1. findCachedBuild() → cache found
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2. verifyCacheConsistency() → creates mojo via getConfiguredMojo()
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3. Reads properties → WITHOUT injection (too early in lifecycle)
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4. Compares to first build's stored values (WITH injection)
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5. MISMATCH → cache invalidated!
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```
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The problem: **validation reads BEFORE injection, storage reads AFTER injection**.
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## Solution
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Capture properties at **validation time** for ALL builds (even when no cache exists). This ensures both validation and storage read at the same lifecycle point.
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### Implementation
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1. **Modified `CacheResult`** to store validation-time mojo events
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2. **Modified `BuildCacheMojosExecutionStrategy`** to capture properties immediately after `findCachedBuild()`
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3. **Modified `save()`** to use validation-time events instead of execution-time events
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### Key Code Changes
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```java
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// In BuildCacheMojosExecutionStrategy.execute():
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result = cacheController.findCachedBuild(session, project, mojoExecutions, skipCache);
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// NEW: Capture validation-time properties for ALL mojos
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Map<String, MojoExecutionEvent> validationTimeEvents =
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captureValidationTimeProperties(session, project, mojoExecutions);
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// Store in result
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result = CacheResult.rebuilded(result, validationTimeEvents);
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```
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```java
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// In save():
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// Use validation-time events instead of execution-time events
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Map<String, MojoExecutionEvent> propertyEvents =
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cacheResult.getValidationTimeEvents() != null
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? cacheResult.getValidationTimeEvents() // Use validation-time
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: executionEvents; // Fallback to execution-time
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List<CompletedExecution> completedExecution =
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buildExecutionInfo(mojoExecutions, propertyEvents);
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```
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### New Timeline (Both Builds)
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```
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First Build:
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1. findCachedBuild() → no cache
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2. captureValidationTimeProperties() → reads WITHOUT injection
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3. Mojos execute → Maven 4 injects (but we don't use these values)
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4. save() uses validation-time properties → stores WITHOUT injection
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Second Build:
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1. findCachedBuild() → cache found
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2. verifyCacheConsistency() → reads WITHOUT injection
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3. captureValidationTimeProperties() → reads WITHOUT injection
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4. Compares to first build → BOTH without injection → MATCH!
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```
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## Benefits Over PR #391
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| Aspect | PR #391 (`ignorePattern`) | This PR (Validation-Time Capture) |
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|--------|--------------------------|-----------------------------------|
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| **Approach** | Workaround: Filter mismatched values | Fix: Eliminate timing mismatch |
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| **Configuration** | Required | None needed |
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| **Flexibility** | Pattern must match version format | Format-agnostic |
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| **Maintenance** | Patterns need updates | No maintenance |
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| **Scope** | Only fixes known patterns | Fixes ALL auto-injected properties |
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## Testing
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Created comprehensive integration tests:
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1. **Maven4JpmsModuleTest** - JPMS module with Maven 4 auto-injection of `--module-version`
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2. **ExplicitModuleVersionTest** - JPMS module with explicit `moduleVersion` configuration
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3. **NonJpmsProjectTest** - Regular Java project without JPMS (ensures no regression)
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4. **MultiModuleJpmsTest** - Multi-module project with mixed JPMS and non-JPMS modules
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All tests verify:
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- ✅ First build creates cache
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- ✅ Second build restores from cache (NO cache invalidation)
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- ✅ NO `ignorePattern` configuration required
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## Backward Compatibility
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- Fully backward compatible
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- Existing caches remain valid
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- No configuration changes required
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- `ignorePattern` still works but is no longer necessary for Maven 4 injection
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## Alternative Approaches Considered
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1. **Store validation-time values only** ❌ - Would lose auditability of what actually executed
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2. **Delay validation until execution** ❌ - Would lose early cache-miss detection performance
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3. **Pattern-based filtering (PR #391)** ❌ - Treats symptom, not root cause
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4. **Maven core changes** ❌ - Outside our control
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5. **Validation-time capture (this PR)** ✅ - Fixes root cause, no configuration needed
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## Related Issues
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- Fixes #375
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- Alternative to #391
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- Related to Maven 4 JPMS module compilation
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## Migration
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No migration needed. This change is transparent to users. Existing projects will benefit automatically.

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