Files
file-manager/AGENTS.md
T
SoftwareApp 0bbee25ab3 Test the interface as a user sees it, and let a debug build tell on itself
Fifteen rendering tests across four files are the first tests in this project that compose a screen,
and they cover the claims that used to be prose only: the app bar's star exists where there is a folder
to star and says Add or Remove according to the state, the selection bar offers Rename to several files
and Details only to one, the batch dialog spells out the names it will produce and refuses a collision
with the file named, the shared name dialog refuses a slash while it is typed, and a favourite that has
gone says "Folder not found" rather than showing a path that is not there. They run on the JVM through
Robolectric - the Compose test artifacts plus the test manifest - so they belong to the same verify.sh
gate as everything else instead of needing a device: 386 tests in total.

Writing them turned up one behaviour worth recording. The batch dialog continues the folder's series by
default, so a collision cannot be shown unless the start number is forced back to 1 - which is precisely
why the feature works in practice, and now also why two of these tests set the field explicitly.

The debug build now enables StrictMode (disk reads and writes, network, leaked closables; logged, not
fatal) and attaches LeakCanary. A file manager is the worst possible app for a blocking disk read on the
main thread, and a debug build is the last place where noticing it is still cheap. Logging rather than a
crash is deliberate: turning a slow screen into a crash on someone's phone is the worse trade. The flag
is read from the manifest, not from BuildConfig, which this build does not generate.

Performance has a number for the first time, and it immediately paid for itself. tools/measure-startup.sh
takes cold start with `am start -W` - median of several runs, one warm-up discarded because the first
launch after an install pays for dexopt - and docs/PERFORMANCE.md records 1814 ms over five runs, in the
debug build, which is the slow case by construction. StrictMode's first run then produced five violations
against that number: 492 ms resolving `app.cacheDir` inside the view-model factory, 397 ms reading free
space with StatFs for every volume inside refresh(), 477 ms of the platform loading its own typefaces,
and two 54 ms OEM font hooks. That is about 1.5 s of main-thread disk I/O in a 1.8 s start, of which
~0.9 s is ours and mechanical to move. Neither of ours is fixed here on purpose: the numbers and the two
fixes are recorded in PERFORMANCE.md, and they are the first items of the speed work.

What is not measured is stated in the same file rather than left to be assumed: folder open at 1 000 /
5 000 / 20 000 files, thumbnail paint while scrolling, and keystroke-to-result all need a `:benchmark`
module and a profileable build under the release package id, and this device waits for a confirmation
dialog on the first install of a new package id. The module is deliberately absent instead of
half-configured: build wiring nobody can run is worse than a recorded gap.

Gate green (map current, detekt, 386 tests, lint), and CHANGELOG, README, AGENTS.md, ROADMAP,
PERFORMANCE.md, EDGE_CASE_TESTING and the regenerated map carry it.
2026-10-17 09:23:11 +02:00

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Markdown

# Working in this repository
**Plain Files** is a file manager for Android: Kotlin and Jetpack Compose, one Gradle module
(`app`), `minSdk` 26, `targetSdk` 36, and **no `INTERNET` permission** — "nothing leaves the
device" is a shipping requirement of this app, not a slogan. It is sold once (no ads, no
subscription, no billing code), and the prose in `docs/` is treated as part of the product.
Two habits shape everything here. **The app is driven on a real device** for anything a user can
see, and what that proved is written down. **A test name is a sentence** about behaviour, so the
suite doubles as the specification.
## Read these two first, and only then the source
| file | why |
|---|---|
| `docs/CODE_MAP.md` | Generated index of the source tree: what each file holds, and every test name in the suite. Start here for "which file is this in?" |
| `docs/ROADMAP.md` | Which milestone is done, the key decisions, and the deliberate deferrals |
Do **not** read `CHANGELOG.md` front to back — it is long, and it is meant to be grepped by
feature name once you know what you are changing.
## Commands
```bash
./tools/verify.sh # the gate: map check, detekt, tests, lint
./tools/verify.sh --release # ...and an R8 release build (what CI runs nightly)
GRADLE_FLAGS=--offline ./tools/verify.sh # when the network is unavailable
./gradlew :app:assembleDebug # then: adb install -r app/build/outputs/apk/debug/app-debug.apk
./tools/measure-startup.sh 5 # cold start, median of five, on the installed device
./gradlew :app:detektBaseline # re-freezes the findings that exist now — think before running it
python3 tools/make-code-map.py # regenerate docs/CODE_MAP.md after touching source
```
CI (`.github/workflows/verify.yml`) runs the same script on every push and pull request, plus a nightly
`--release` build, because R8 is the one check nothing else performs and it has hidden a real defect
here before. `git config core.hooksPath .githooks` runs it before every push as well.
The detekt gap it leaves — the findings in `config/detekt/baseline.xml` — is a **ratchet**: new
findings fail the build, existing ones are parked until the file they live in is touched for another
reason. `tools/` holds the gate and the generators; `config/detekt/` holds the rules and that baseline.
## Where things live, and the one rule about direction
```
core/ pure Kotlin, no Android imports: paths, names, kinds, sorting, planning
data/ storage backends (all-files access, SAF), volumes, shares, SQLite search/trash/favourites
domain/ operations over a source: copy/move/delete/rename, archives, search, duplicates
service/ the foreground service that keeps a long operation alive
ui/ Compose: browser/, viewer/, usage/, trash/, duplicates/, theme/
text/ domain enum to string resource
```
The dependency direction is `ui → domain → data → core`, and `core/` importing `android.*` or
`androidx.*` is a test failure, not a matter of taste: it is what keeps the trickiest logic
testable without Robolectric. `docs/CODE_MAP.md` has the per-file detail.
## Non-negotiables
Each of these is enforced somewhere, so breaking one fails a test, lint, or a reviewer's first
comment. `app/src/test/java/…/ProjectInvariantsTest.kt` holds the source-level ones.
- **No new permission, and never `INTERNET`.** The manifest's permission set is asserted exactly;
adding one means deciding it, explaining it in the manifest comment and the README, and updating
that list deliberately.
- **Every user-visible string comes from `strings.xml`.** The debug build enables a pseudo-locale
(`values-en-XA`), so untranslated text is visible on screen as unaccented text.
- **A name is one path segment.** `core/FileNames.isUsableName` is the only implementation; never
inspect `/` yourself. `StoragePath.child("a/b")` resolves *into a subfolder*, so an unguarded
call renames or creates something the dialog never offered.
- **Nothing is overwritten silently.** Operations refuse rather than destroy; deletes go through
the trash (24-hour window) and offer undo; a batch that cannot succeed is refused as a whole
rather than performed until it hits the problem.
- **Comments explain why, not what.** The house style is a KDoc paragraph per file and type that
says what it is for and what was rejected — decisions and limits, not restatements of the code.
- **A test name is a sentence about behaviour** (`a batch rename is a single undo step`), because
the names are read as the spec. Logic gets behaviour tests, rules about the shape of the project
get source-level tests, and **what a user sees gets a Compose rendering test** — those run on the
JVM through Robolectric, so they are part of the same gate rather than needing a device.
- **The docs are part of the change.** `CHANGELOG.md` (Added/Changed/Fixed, in the house voice),
the `ROADMAP.md` milestone table, the README if a claim changed, and `docs/EDGE_CASE_TESTING.md`
for anything only a device could confirm.
## Traps that have cost real time here
- **MIUI blocks `adb install` twice over.** Developer options needs *Install via USB*, and each
install then waits for a confirmation dialog that times out on its own. A bare
`INSTALL_FAILED_USER_RESTRICTED` means the dialog was answered late, not that the APK is bad.
- **Never run `assembleDebug` and `adb install` in one parallel batch.** They race, the install
takes the previous APK, and the feature you just wrote appears to be missing.
- **R8 has hidden real bugs.** A class reached only by reflection, or named only from a resource,
is stripped from the release build while debug works perfectly — this happened with `coil-video`,
where video frames decoded in debug and quietly fell back to icons for real users. When debug and
release disagree, assume the shrinker removed something.
- **`adb input text` does not deliver a `/`.** Send `input keyevent 76` instead. The slash is worth
testing at all because the field *accepts* it and the dialog is what refuses it.
- **Long-press multi-select via `input swipe x y x y 900` works, but not every time** — it has also
landed as a plain tap. A flaky gesture is a reason to look at the screen, not to distrust the code.
- **The debug build is a separate package** (`…filemanager.debug`), so it installs beside a release
build and the two can be compared directly.
- **detekt 1.23 cannot run on JDK 25.** It parses the version string of the JVM it runs on and
throws `25.0.4.1` as the entire error message, which is why `:app:detekt` drives the CLI on a 21
launcher. A bare version number as a build failure is this, not the code — and a **JDK 21 has to be
installed** for the toolchain to find: Gradle does not download one here.
- **A detekt baseline has to exist before it can be read.** It starts as an empty document on
purpose; `--create-baseline` cannot conjure the path it was told to consult.
## Documentation map — read on demand
| file | what it is for |
|---|---|
| `README.md` | The tour: features, layout, build, and the honest **known limitations** |
| `CHANGELOG.md` | The reasoning behind each change. Grep it; do not read it end to end |
| `docs/ROADMAP.md` | Milestones with their evidence, the key decisions, the deferrals |
| `docs/EDGE_CASE_TESTING.md` | What was verified, on which device or AVD, and what was not |
| `docs/PERFORMANCE.md` | The numbers that exist, and the ones that deliberately do not yet |
| `docs/PLAY_RELEASE_CHECKLIST.md` | Release only — work it in order |
| `docs/COMPETITIVE_ANALYSIS.md`, `docs/MONETISATION.md`, `docs/STORE_LISTING.md` | Product context, pricing, and length-checked listing copy |
| `PRIVACY.md` | The policy text the store listing points at |
## Definition of done
1. `./tools/verify.sh` green — the map current, detekt, the unit tests and lint in one command.
2. `python3 tools/make-code-map.py` run, so that `--check` passes.
3. A `CHANGELOG.md` entry in the house voice: what changed, why, what was rejected, and what was
verified rather than assumed.
4. Anything a user can see driven on a device or emulator, with the result written into
`docs/EDGE_CASE_TESTING.md` — including what was deliberately left untested, and why.
5. A commit whose subject is a sentence about the change and whose body explains the reasoning.
The diff already says what changed; the message is there for why it is this way.