# Release Notes

All notable changes to VortexCollisions.jl.

This package is pre-1.0, so *every* minor release is potentially breaking in the sense of
[SemVer](https://semver.org) for `0.x` versions. The sections below name what actually
changed, so that a compat-only bump can be told apart from a rename or a change in results.

This file was started on 2026-08-31 and deliberately holds no entries. Nothing has been
released yet — there are no tags, and `Project.toml` stands at `0.1.0` — so the development
history that predates this file is in `git log` alone, reaching back to 2017. It is named as a
gap rather than reconstructed, because a changelog assembled after the fact loses exactly the
reasoning that makes it worth keeping.

## [Unreleased] — targeting 0.1.0

### New Features

- **Continuous integration.** The repository had no `.github` directory at all; it now carries the
  same `CI.yml`, `CompatHelper.yml`, `Documenter.yml` and `TagBot.yml` as every other repository in
  the tree — the test suite over two Julia versions and three operating systems, a doctest job, and
  coverage reporting.
- **A documentation build.** `docs/` previously held one untracked PDF; it now has `make.jl`,
  `Project.toml` and a two-page manual, so `Documenter` has something to build and to deploy.
  That PDF — `effective_collision_operatos.pdf`, a personal note from April 2017 on a
  pseudospectral algorithm for the collision operators of Morrison, *Physica D* 1986 — **has now
  moved to `Projects/Metriplectic Relaxation/`**, whose subject it is. Nothing referenced it:
  neither `make.jl` nor any page under `docs/src` mentions it, so the documentation build is
  unaffected. It was tracked only by the commit that added this documentation build, and it is
  in `git log` from there.
- **The test suite follows the tree's test convention.** The test dependencies are in
  `test/Project.toml`, and `Project.toml` has no `[extras]` or `[targets]`. `runtests.jl` lists
  each test file as a `@safetestset` in the `core` group, so each file runs in its own module. The
  test files have the names of the `src/` files they test, and the shared functions are in
  `test/helpers/functions.jl`. `test/quality/aqua.jl` runs Aqua, and `[compat]` gains
  `Distributed = "1"`, `LinearAlgebra = "1"` and `SharedArrays = "1"` so that its compat-bounds
  check passes (issue #2). The kernel test defines its own `mfunc_one!` and `hfunc_ϕ!`
  with the `grid` argument that the operator passes, because it no longer sees the methods of the
  other test file. `runprofiler.jl` and `runtimings.jl` are timing scripts, not tests, and move from
  `test/` to `scripts/`. Nothing under `src/` changes.

### Bug Fixes

- **The documentation build named a branch that does not exist.** `docs/make.jl` set both
  `edit_link` and `devbranch` to `"master"`, while the default branch is `main` and the remote
  carries no `master` at all. So `deploydocs` never deployed the development documentation, and
  every "Edit on GitHub" link in the built manual pointed at a dead path. Both now say `"main"`.
- **Five methods failed on every call.** The two `fourier_quadrature` methods with a matrix of
  weight matrices called the misspelled `fourier_quarature` and threw an `UndefVarError`. The two
  `trapezoidal_quadrature` methods with a matrix of weight matrices typed their result with the
  unbound `CT` and threw an `UndefVarError`. `convolution_kernel_fourier!` built its weight arrays
  with `Array{Array{RT, 2}}(2, 2)`, a constructor without `undef` that Julia 1.0 removed, and threw a
  `MethodError`. All five now run. Tests check the quadratures against their scalar method, and
  the Fourier kernel against the trapezoidal kernel.

### Changed

- **Julia 1.12 is the floor** (`[compat] julia = "1.12"`, from 1.10). A breaking change under
  this package's pre-1.0 convention: a caller on Julia 1.10 or 1.11 can no longer install this
  version. The repository records no reason for the new floor, and no code or test workaround
  existed for the old one, so nothing in the package's code changes.
- **Coverage and cache in CI.** CI uploads coverage from the `Julia 1 - ubuntu-latest` job instead
  of `Julia min`, and a test job saves the Julia cache only when it succeeds.
- **Code quality and API refinement.** Loops in src/ now iterate `axes`/`eachindex` instead of
  `1:size`/`1:length` via fatou `index-from-length` checks; 13 findings where the index also
  reaches an array of another shape, or another axis, are suppressed with
  `# fatou-ignore index-from-length`. The unused `c` vector in the generator of `timestep!`
  (src/time_integration.jl) is deleted. A test for `update_field!` is added
  (test/time_integration.jl). The exported `apply_operator!(::Vector, ::Matrix, ::Vector)` now
  raises `DimensionMismatch` when `op` and `v` have different lengths; previously, a longer `v` was
  silently filled only in part, and a shorter `v` raised `BoundsError`.
- **The Fokker-Planck kernel test moves to `test/integration/`.** The test convention keeps a test
  file at the top level of `test/` only where it mirrors `src/<name>.jl`.
  `test/fokker_planck_operator_kernel.jl` mirrors no source file; it tests
  `src/fokker_planck_operator.jl` together with `src/grid.jl` and `src/fourier_transform.jl`, and
  `test/fokker_planck_operator.jl` already mirrors the operator, so it is now
  `test/integration/fokker_planck_operator_kernel.jl`. Only its include path of
  `helpers/functions.jl` and its path in `runtests.jl` change.
- **Aqua's floor in `test/Project.toml` is 0.8.14** (from `"0.8"`). The `Downgrade` job resolves
  `Project.toml` and `test/Project.toml` together at their lower bounds on Julia 1.12 and runs the
  tests there. Aqua 0.8.0 to 0.8.13 read `Core.TypeName.mt`, which Julia 1.12 no longer has, so
  the piracy check throws a `FieldError`; 0.8.14 is the first release that reads
  `Core.methodtable` instead. No other floor changes: the merged resolve reaches every lower bound
  of both files.

### Breaking Changes

- **The repository moved from `DDMGNI` to the `JuliaPlasma` organisation.** It is now
  `github.com/JuliaPlasma/VortexCollisions.jl`, and the documentation deploys to
  `JuliaPlasma.github.io/VortexCollisions.jl`. GitHub redirects the old path, so an existing
  clone and an `]add` of the old URL both keep working — but they resolve through a redirect
  rather than to the real location, so pinned URLs are worth updating. `README.md`, `docs/make.jl`
  and `docs/src/index.md` name the new path.
- **A `[compat]` section, where there was none.** `julia`, whose floor the first entry under
  Changed above sets to 1.12 and which the CI matrix resolves its lower entry from, plus bounds
  for the four non-stdlib dependencies: `AbstractFFTs = "1"`, `FFTW = "1.3.1"`, `HDF5 = "0.17"`,
  `ProgressMeter = "1"`, matching what the manifest resolves today. An unbounded dependency is free
  to break the package on its next breaking release. `FFTW` settles at 1.3.1 rather than `"1"`:
  `AbstractFFTs = "1"` and FFTW 1.0.0 to 1.3.0 require `AbstractFFTs` 0.5, so the two lower bounds
  cannot hold at once, and the `Downgrade` job named FFTW as unreachable at its old value.