feat(config): group task cache fields under cache

[wan9chi]

Motivation

env, untrackedEnv, input, and output only apply when caching is enabled, but that isn't obvious when they sit at the top level of a task next to unrelated fields such as command, cwd, and dependsOn. For example, env reads like it sets or passes environment variables for every run, not like a cache setting. Grouping these fields under cache makes the relationship explicit:

// before
{ "command": "tsc", "cache": true, "env": ["NODE_ENV"], "input": ["src/**"] }
// after
{ "command": "tsc", "cache": { "env": ["NODE_ENV"], "input": ["src/**"] } }

It also gives future cache settings a place to go. For example, the upcoming remote cache option can be added as cache: { remote: ... } instead of cache: true, remoteCache: ....

Summary

Task config	Result
cache omitted, cache: true, cache: {}	Caching enabled with default settings (all three are the same)
cache: { env, untrackedEnv, input, output }	Caching enabled with these settings
cache: false	Caching disabled
Top-level env / untrackedEnv / input / output	Error when the task graph loads, with migration instructions

• cache accepts true, false, or an object. cache: {} enables caching with all default settings, and cache: true or an omitted cache means the same thing.
• This is a breaking change: env, untrackedEnv, input, and output are no longer accepted at the top level of a task.
• A migrated config resolves to the same cache config as the old top-level form, so migrating doesn't invalidate existing cache entries.

Migration

We'll add migration logic in vite-plus that moves top-level env, untrackedEnv, input, and output into cache, and the vite-plus changelog will ask users to migrate.

Configs that still use the top-level fields fail with one error that lists every affected task and points to vp migrate and the config docs:

error: Failed to load task graph
* Cache settings `env`, `input`, `output` must be set under `cache` in tasks app#build, app#test, e.g. `cache: { env: [...] }`. Run `vp migrate` to update your config automatically. See https://viteplus.dev/config/run for details.

[github-actions]

fspy benchmark

linux

dynamic/launch             change  -0.52%  [-13.29% .. +19.12%]  overhead  +268.98%
dynamic/access             change  -2.59%  [-18.90% ..  +2.54%]  overhead   +14.02%
dynamic/access-relative    change  +0.00%  [ -4.15% ..  +2.45%]  overhead   +67.40%
dynamic/access-contended   change  +0.21%  [ -4.84% ..  +7.77%]  overhead   +43.75%
static/launch              change  -0.08%  [ -9.97% .. +14.45%]  overhead  +712.10%
static/access              change  +0.59%  [ -0.79% ..  +3.29%]  overhead +1451.47%
static/access-relative     change  +0.03%  [ -2.04% ..  +1.24%]  overhead +1955.09%
static/access-contended    change  +0.60%  [ -1.62% ..  +7.42%]  overhead +1330.59%

macos

dynamic/launch             change  -0.64%  [ -4.15% ..  +3.48%]  overhead  +224.72%
dynamic/access             change  -0.69%  [ -2.41% ..  +1.72%]  overhead    +2.90%
dynamic/access-relative    change  +0.11%  [ -4.02% ..  +4.41%]  overhead  +266.46%
dynamic/access-contended   change  +4.72%  [ -9.85% .. +38.37%]  overhead    +6.39%

windows

dynamic/launch             change  +0.49%  [ -3.78% ..  +3.33%]  overhead   +26.50%
dynamic/access             change  +0.18%  [ -2.14% ..  +6.29%]  overhead    +1.11%
dynamic/access-relative    change  -0.17%  [ -8.55% ..  +2.14%]  overhead    +1.26%
dynamic/access-contended   change  +0.35%  [ -8.18% .. +11.19%]  overhead    +2.82%

[fengmk2]

LGTM