gnodet opened a new issue, #13499:
URL: https://github.com/apache/maven/issues/13499
## Context
As part of assessing Tycho's readiness to migrate to the Maven 4 API, we
identified
areas where the v4 API/SPI surface is insufficient for deep build
extensions. Tycho is
a useful stress-test case because it touches nearly every Maven extension
point:
lifecycle participation, dependency resolution, reactor graph, plugin realm
management,
and classloading.
This issue tracks gaps not already fully covered by #13460 sub-issues.
## Gaps
### 1. Lifecycle Participation SPI — implicitly in scope for #13464, not
explicit
Tycho's `TychoMavenLifecycleParticipant` uses `afterProjectsRead()` to
resolve the P2
target platform and inject dependencies into every `MavenProject` before any
mojo
executes. `TychoProjectExecutionListener` uses
`beforeProjectLifecycleExecution()` for
lazy per-project resolution with execution plan inspection.
The v4 `Listener`/`Event` mechanism is too generic — it lacks structured
callbacks with
mutable project access. No equivalent of `AbstractMavenLifecycleParticipant`
or
`ProjectExecutionListener` exists in `org.apache.maven.api.spi`.
**Needed:** A lifecycle participation SPI with:
- `afterProjectsRead` equivalent (with mutable project access)
- Per-project before/after execution callbacks (with execution plan access)
- Session end callback
This overlaps with #13464 (lifecycle engine) and #13462 (session inversion),
but the
*public SPI contract* isn't explicitly scoped in either.
### 2. Workspace Reader SPI — partially addressed by #13094
PR #13094 introduces `org.apache.maven.api.spi.WorkspaceReader` with
`findArtifact()`
and `findVersions()`. This covers the base `WorkspaceReader` contract.
However, Tycho's `TychoWorkspaceReader` implements `MavenWorkspaceReader`
which adds
**`findModel(Artifact)`** — used to generate synthetic POMs for P2 artifacts
that have
no Maven pom.xml. This method is not in the PR #13094 SPI.
**Needed:** Consider adding `findModel()` (or equivalent) to the v4
`WorkspaceReader`
SPI for extensions that resolve non-Maven artifacts requiring synthetic model
generation.
### 3. Scoped SPI Discovery — partially covered by #13465 + #13223
Tycho's `DefaultPluginRealmHelper` uses
`BuildPluginManager.getPluginRealm()`,
`MavenPluginManager.getPluginDescriptor()`, and
`PlexusContainer.lookupList()` to
discover SPI extensions contributed by plugin dependencies. It switches
thread context
classloaders to plugin ClassRealms for scoped lookups.
**Needed:**
- Plugin descriptor/dependency introspection API
- Scoped service lookup (find services contributed by a specific plugin's
classloader)
- Intersects with #13223 Layer 1 (per-realm import descriptor) and laeubi's
comment
about plugins declaring SPI artifacts
### 4. ClassRealm Abstraction — partially covered by #13223
`PlexusFrameworkConnectServiceFactory` manages an embedded Equinox framework
keyed by
`ClassRealm`, using `realm.getParentRealm()`, `realm.getImportRealms()`,
`realm.loadResourcesFromSelf()`, and cross-realm reflection for framework
sharing.
**Needed:** A stable classloader abstraction (or extension-classloader SPI)
providing:
- Classpath resource enumeration for a plugin/extension
- Identity semantics for classloader-scoped caching
- Cross-boundary service sharing without reflection
#13223 Layer 1 would solve the `tycho-maven-plugin`-as-extension-shim
problem, but
the embedded OSGi framework management needs stable classloader primitives.
## Already tracked
- **Reactor graph SPI** — #13463 explicitly acknowledges a new v4 API design
is needed.
Tycho's `TychoGraphBuilder` would benefit from a contributor/decorator
model (add
edges to the graph) rather than requiring full graph builder replacement.
- **LegacySupport** — should be obsoleted by proper session scoping in
#13462.
## Cross-references
| Gap | Related |
|-----|---------|
| Lifecycle participation SPI | #13464, #13462 |
| Workspace reader SPI | #13094, #13460 |
| Scoped SPI discovery | #13465, #13223 |
| ClassRealm abstraction | #13223, #13465 |
| Reactor graph SPI | #13463 (tracked) |
| LegacySupport | #13462 (tracked) |
<!-- AI-Agent-Disclosure -->
> 🤖 Drafted with Claude Code (Claude Opus 4.6, interactive mode). Reviewed
and confirmed by @gnodet before submission.
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