GROOVY-12223: Introduce hidden class support

[daniellansun]

https://issues.apache.org/jira/browse/GROOVY-12223

[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.50.

Benchmark suite	Current: 58063be	Previous: 544c016	Ratio
org.apache.groovy.bench.AryBench.java ( {"n":"1000"} )	0.11873074707054951 ms/op	0.059375013802723364 ms/op	2.00

This comment was automatically generated by workflow using github-action-benchmark.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 77.34807% with 41 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.0142%. Comparing base (b67fc73) to head (58063be).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...codehaus/groovy/runtime/ProxyGeneratorAdapter.java	78.4810%	5 Missing and 12 partials ⚠️
...haus/groovy/runtime/metaclass/ReflectorLoader.java	55.5556%	9 Missing and 3 partials ⚠️
...ava/org/apache/groovy/util/HiddenClassDefiner.java	87.0370%	4 Missing and 3 partials ⚠️
...roovy/reflection/ClassLoaderForClassArtifacts.java	76.1905%	1 Missing and 4 partials ⚠️

Additional details and impacted files

@@                Coverage Diff                 @@
##               master      #2755        +/-   ##
==================================================
+ Coverage     69.9742%   70.0142%   +0.0399%     
- Complexity      35502      35575        +73     
==================================================
  Files            1557       1558         +1     
  Lines          131667     131799       +132     
  Branches        24166      24200        +34     
==================================================
+ Hits            92133      92278       +145     
+ Misses          31193      31164        -29     
- Partials         8341       8357        +16     

Files with missing lines	Coverage Δ
...roovy/reflection/ClassLoaderForClassArtifacts.java	79.3103% <76.1905%> (+4.3103%)	⬆️
...ava/org/apache/groovy/util/HiddenClassDefiner.java	87.0370% <87.0370%> (ø)
...haus/groovy/runtime/metaclass/ReflectorLoader.java	60.4167% <55.5556%> (+60.4167%)	⬆️
...codehaus/groovy/runtime/ProxyGeneratorAdapter.java	88.3459% <78.4810%> (-1.5029%)	⬇️

... and 8 files with indirect coverage changes

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[github-actions]

JMH summary — classic (commit 2a8d895)

Speedup vs trailing 90-day baseline on gh-pages. Higher = faster.
1.00 = in line with history. Per-benchmark ratio, geomean within group.
Time-per-op units inverted so direction is consistent. The calibrated
column divides out this runner's speed vs the baseline hardware, as
measured by Groovy-independent pure-Java ruler benchmarks.

Group	Speedup	Calibrated	n
bench	0.993 ×	0.987 ×	99
core	0.995 ×	0.888 ×	83
grails	0.865 ×	0.829 ×	80

_{Runner calibration (this run vs baseline hardware): bench 1.00× (26 rulers) · core-ag 1.12× (3 rulers) · core-hz 1.12× (3 rulers) · grails-ad 1.12× (3 rulers) · grails-ez 0.99× (3 rulers)}

_{Baseline: dev/bench/jmh/<part>/classic/data.js on gh-pages, trailing 90 days. Daily dashboard · Per-suite raw data}

[github-actions]

JMH summary — indy (commit 2a8d895)

Speedup vs trailing 90-day baseline on gh-pages. Higher = faster.
1.00 = in line with history. Per-benchmark ratio, geomean within group.
Time-per-op units inverted so direction is consistent. The calibrated
column divides out this runner's speed vs the baseline hardware, as
measured by Groovy-independent pure-Java ruler benchmarks.

Group	Speedup	Calibrated	n
bench	0.971 ×	0.990 ×	99
core	3.061 ×	3.107 ×	83
grails	4.350 ×	4.220 ×	80

_{Runner calibration (this run vs baseline hardware): bench 0.98× (26 rulers) · core-ag 0.99× (3 rulers) · core-hz 0.98× (3 rulers) · grails-ad 1.13× (3 rulers) · grails-ez 0.96× (3 rulers)}

_{Baseline: dev/bench/jmh/<part>/indy/data.js on gh-pages, trailing 90 days. Daily dashboard · Per-suite raw data}

[blackdrag]

• HiddenClassDefiner contains method used only in tests
• ProxyGeneratorAdapter and ReflectorLoader seems to duplicate work already done in HiddenClassDefiner, while still using HiddenClassDefiner

But the big point for me is MethodHandles.lookup(). It has the javadoc:

Returns a lookup object with full capabilities to emulate all supported bytecode behaviors of the caller. These capabilities include full privilege access to the caller. Factory methods on the lookup object can create direct method handles for any member that the caller has access to via bytecodes, including protected and private fields and methods. This lookup object is created by the original lookup class and has the ORIGINAL bit set. This lookup object is a capability which may be delegated to trusted agents. Do not store it in place where untrusted code can access it.

This method is caller sensitive, which means that it may return different values to different callers. In cases where MethodHandles.lookup is called from a context where there is no caller frame on the stack (e.g. when called directly from a JNI attached thread), IllegalCallerException is thrown. To obtain a lookup object in such a context, use an auxiliary class that will implicitly be identified as the caller, or use publicLookup() to obtain a low-privileged lookup instead.

So if I create a Lookup for HiddenClassDefinerTest in HiddenClassDefinerTest I will get full access. But if I create that in the same class for java.lang.String, I will not get full access. In practice this usually means that unless the class creates the lookup (for example during invokedynamic) it is useless for many things. So if you need private module access, then MethodHandles.lookup() is most likely not the way to go.
Which means I don`t think that the intend of HiddenClassDefiner.privateLookupIn and usuability go hand in hand here.

[sonarqubecloud]

Quality Gate passed

Issues
6 New issues
0 Accepted issues

Measures
0 Security Hotspots
88.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[testlens-app]

✅ All tests passed ✅

🏷️ Commit: 58063be
▶️ Tests: 108769 executed
⚪️ Checks: 31/31 completed

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