improve speed of generator

[Picazsoo]

For me these changes sped up sample regen via ./bin/generate-samples.sh from 3m9s to 1m59s

I have another branch where I prevent unnecessary recompilation of regex patterns and am down to 1m54s.
This is on Ryzen 9950x3D with 64GB ram. I guess the improvement will be more noticeable on slower machines.

Update: Down to 1m45s.

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---

Summary by cubic

Speed up code generation by caching template contents and resolved paths, adding per‑executor engine/template caches, and tightening duplicate/file checks. This reduces CPU and disk I/O with no output changes.

• Performance

  • Cache template contents in TemplateManager; cache resolved template paths (including misses) in GeneratorTemplateContentLocator; precompile file‑separator pattern for classpath paths; add early file‑length check before byte comparison.
  • Add per‑executor caches in HandlebarsEngineAdapter (engines and compiled templates) and MustacheEngineAdapter (compiled templates) using ConcurrentHashMap; no cache clearing or cross‑executor sharing.
  • Use a lowercased shadow set for O(1) case‑insensitive duplicate path detection in DefaultGenerator.
  • In DefaultCodegen: precompile trailing‑digits pattern; cache Unicode remove‑char regexes; speed up case‑insensitive unique name generation.

• Refactors

  • Consistent logging placeholders (including throwable), final fields, simpler boolean/null checks, and small null‑safety tweaks. No behavior changes.

^{Written for commit 9941a95. Summary will update on new commits.}

[cubic-dev-ai]

2 issues found across 5 files

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="modules/openapi-generator/src/main/java/org/openapitools/codegen/templating/MustacheEngineAdapter.java">

<violation number="1" location="modules/openapi-generator/src/main/java/org/openapitools/codegen/templating/MustacheEngineAdapter.java:73">
P2: Template cache key omits executor, so cached mustache templates can be reused with stale template sources/partials from a previous executor.</violation>
</file>

<file name="modules/openapi-generator/src/main/java/org/openapitools/codegen/templating/HandlebarsEngineAdapter.java">

<violation number="1" location="modules/openapi-generator/src/main/java/org/openapitools/codegen/templating/HandlebarsEngineAdapter.java:118">
P2: `IOException` from Handlebars compilation is converted into `RuntimeException`, changing the method’s checked-exception behavior and breaking expected caller error handling.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[cubic-dev-ai]

1 issue found across 3 files (changes from recent commits).

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="modules/openapi-generator/src/main/java/org/openapitools/codegen/templating/MustacheEngineAdapter.java">

<violation number="1" location="modules/openapi-generator/src/main/java/org/openapitools/codegen/templating/MustacheEngineAdapter.java:82">
P2: Executor-bound template cache invalidation is non-atomic, allowing cross-executor template contamination under concurrent calls.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[cubic-dev-ai]

No issues found across 6 files

[wing328]

thanks for the PR

cc @OpenAPITools/generator-core-team

[Picazsoo]

Yeah - this one should definitely wait for the next release (not the imminent one) to be on the safe side.