Separate context code into smaller files; remove some dead code

[penelopeysm]

This PR purely shuffles code around, there are no real code changes.

[github-actions]

Benchmark Report for Commit dd3a13c

Computer Information

Julia Version 1.11.7
Commit f2b3dbda30a (2025-09-08 12:10 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 4 × AMD EPYC 7763 64-Core Processor
  WORD_SIZE: 64
  LLVM: libLLVM-16.0.6 (ORCJIT, znver3)
Threads: 1 default, 0 interactive, 1 GC (on 4 virtual cores)

Benchmark Results

┌───────────────────────┬───────┬─────────────┬───────────────────┬────────┬────────────────┬─────────────────┐
│                 Model │   Dim │  AD Backend │           VarInfo │ Linked │ t(eval)/t(ref) │ t(grad)/t(eval) │
├───────────────────────┼───────┼─────────────┼───────────────────┼────────┼────────────────┼─────────────────┤
│ Simple assume observe │     1 │ forwarddiff │             typed │  false │            9.1 │             1.5 │
│           Smorgasbord │   201 │ forwarddiff │             typed │  false │          649.9 │            43.6 │
│           Smorgasbord │   201 │ forwarddiff │ simple_namedtuple │   true │          424.3 │            53.0 │
│           Smorgasbord │   201 │ forwarddiff │           untyped │   true │         1153.5 │            30.8 │
│           Smorgasbord │   201 │ forwarddiff │       simple_dict │   true │         6561.6 │            29.2 │
│           Smorgasbord │   201 │ reversediff │             typed │   true │         1052.6 │            40.3 │
│           Smorgasbord │   201 │    mooncake │             typed │   true │         1001.8 │             4.6 │
│    Loop univariate 1k │  1000 │    mooncake │             typed │   true │         5871.4 │             4.3 │
│       Multivariate 1k │  1000 │    mooncake │             typed │   true │         1015.2 │             8.8 │
│   Loop univariate 10k │ 10000 │    mooncake │             typed │   true │        66007.6 │             3.9 │
│      Multivariate 10k │ 10000 │    mooncake │             typed │   true │         8469.8 │            10.1 │
│               Dynamic │    10 │    mooncake │             typed │   true │          140.0 │            11.6 │
│              Submodel │     1 │    mooncake │             typed │   true │           12.5 │             5.1 │
│                   LDA │    12 │ reversediff │             typed │   true │         1027.2 │             2.1 │
└───────────────────────┴───────┴─────────────┴───────────────────┴────────┴────────────────┴─────────────────┘

[penelopeysm]

This was no longer used anywhere

[penelopeysm]

TLDR:

contexts.jl used to contain all the parent contexts, those have been moved to their own files.

• Now contexts.jl includes only the interface methods for AbstractContext. In a sense it's more like abstract_context.jl.
• It's still not fully documented exactly what the interface for AbstractContext is. I'd like to make that a separate PR though because I actually think NodeTrait can be removed which would simplify matters there.

context_implementations.jl used to contain stray methods for DefaultContext, PrefixContext, and submodels. Those have been sent to their respective files.

transforming.jl basically existed to define DynamicTransformationContext so I moved it into contexts/ too. That file also defined some methods for linking AbstractVarInfo so those were moved to abstract_varinfo.jl too since they form part of the interface methods for it.

[codecov]

Codecov Report

❌ Patch coverage is 77.77778% with 52 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (breaking@5a98037). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
src/contexts/conditionfix.jl	70.44%	47 Missing ⚠️
src/contexts/prefix.jl	91.17%	3 Missing ⚠️
src/submodel.jl	50.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             breaking    #1050   +/-   ##
===========================================
  Coverage            ?   82.20%           
===========================================
  Files               ?       41           
  Lines               ?     3810           
  Branches            ?        0           
===========================================
  Hits                ?     3132           
  Misses              ?      678           
  Partials            ?        0           

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[github-actions]

DynamicPPL.jl documentation for PR #1050 is available at:
https://TuringLang.github.io/DynamicPPL.jl/previews/PR1050/

[mhauru]

All good from me