71 lines
7.5 KiB
Markdown
71 lines
7.5 KiB
Markdown
# Learnings — tofu-core
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Conventions, patterns, and successful approaches discovered during work on this plan.
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_Auto-scaffolded by /start-work. Append new entries below - never overwrite._
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---
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## Task 2: Config Loading (src/tofu/config.d)
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### toml package API (v1.0.0, Kripth/toml)
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- Import: `import toml;` → provides `TOMLDocument`, `TOMLValue`, `parseTOML`, `TOMLException`, `TOMLParserException`
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- `TOMLDocument` has `alias table this` — acts like `TOMLValue[string]` AA
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- Access sections: `doc["core"]` returns `TOMLValue` with `type == TOML_TYPE.TABLE`
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- Access string values: `doc["core"]["key"].str` (throws if type mismatch)
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- Check existence: `"key" in doc` returns `TOMLValue*` (null if absent)
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- `parseTOML()` is `@system` — must wrap in `@trusted` block when calling from `@safe` code
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- Keys without `.str` / `.integer` access will throw `TOMLException`
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### D language gotchas
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- **Nested function declarations**: D does NOT allow `void foo() { ... }` inside a function body. Use lambdas: `auto foo = () { ... }; foo();` or anonymous `() @trusted { ... }();`
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- **`version` is a keyword**: Cannot use `string version;` as field name — use `string version_;` or initialize with `= ""`
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- **`parseTOML` is `@system`**: The toml package's parse function isn't marked `@safe` — must wrap in `@trusted` lambda
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- **`std.file.readText` is `@system`**: Same — wrap in `@trusted`
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- **`std.process.environment.get()`**: Returns empty string when env var is unset; `"VAR" in environment` checks existence but `environment.get("VAR", "default")` is cleaner
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- **`stderr.writefln` is `@safe`** in recent DMD (2.106+) — usable directly in `@safe` code
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- **AA `in` operator**: Returns pointer (`V*`) or `null` — must check for null before dereferencing
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### Pattern: env-overrideable config loading
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- Priority: env vars > TOML file > hardcoded defaults
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- TOML read happens BEFORE env override — so TOML values serve as base, env vars overwrite
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- Missing config file → no error, just skip to defaults
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- Malformed TOML → `TOMLParserException` caught, warning to stderr, fall back to defaults
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- Testability: `load()` accepts optional `envOverrides` map and explicit `configFile` path to avoid real env/filesystem
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### Config design decisions
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- `TOFU_CONFIG` env var overrides default config file path (`~/.config/tofu/config.toml`)
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- `~` in default paths expanded with `std.path.expandTilde`
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- All path fields default to empty string when "find on PATH" — no hardcoded binary paths
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- `defaultJobs` typed as `int` (not `size_t`/`ulong`) since it's a user-facing count
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### buildOptions warningsAsErrors deprecation
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- DUB warns about `warningsAsErrors` in `buildOptions` — recommends `buildRequirements` instead
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- Not blocking, informational only
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## Task 3 — `tofu.log` (colored, NO_COLOR-aware logging)
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- **dmd 2.112 gotcha**: the `std.stdio` globals `stdout`/`stderr` are `@system` to *access* — `makeGlobal` uses `__gshared File result`, which fails `@safe` inference. An `@safe` function cannot call `stdout.writeln(...)` directly. Fix: route every write through a tiny `@trusted` helper (`writeStdout(string)`/`writeStderr(string)`), keep the public log functions `@safe`. Compiler hint: *"using `__gshared` instead of `shared` makes it fail to infer `@safe`"*.
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- **`std.process.environment` (dmd 2.112)**: it is an `abstract final class` of *static* methods — `environment.get(name)` is `@safe` and returns `null` when the var is unset (so "NO_COLOR set" == `get !is null`, even for an empty string). `environment["K"] = v` and `environment.remove(name)` are `@trusted`. NOT deprecated in 2.112.
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- **Testable color decision**: make `colorEnabled()` re-read the environment on every call instead of caching in `static this()`. Enables NO_COLOR/TERM tests without restarting the process. Costs one `getenv` per log line — negligible.
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- **Env save/restore in unittests**: a `private struct ColorEnv` (in `version(unittest)`) that snapshots NO_COLOR+TERM in its ctor and restores them in `~this()` (destructor) — `auto env = ColorEnv("1", "xterm")` scopes the restore. `null` value = remove the var. Double-destruction from a copied temporary is harmless (restore is idempotent).
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- **Capturing stdout/stderr in unittests**: swap the global `stdout`/`stderr` File to a `File(name, "w+")`, write, `flush()`, swap back, then `rewind()` + `readln()`. Restore the global before the temp File's destructor runs.
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- **zeta log format details**: `warn ` paints the *whole prefix* yellow (`paint("yellow", "warn ") ~ msg`), but `error` paints *only the word* then `" " ~ msg` (`paint("red","error") ~ " " ~ msg`). Assertion must expect `\x1b[31merror\x1b[0m failed deploy` — the reset code sits between "error" and the message.
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- **`version` is a D keyword** — cannot be used as a struct field / identifier (trap for the parallel `types.d` work).
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- **`std.stdio.writeln` flushes per call** — already satisfies "no buffering"; no explicit `flush()` needed in production paths.
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- **Verifying a single module without the full build**: `dmd -main -unittest -i src/tofu/log.d` runs just that module's unittests when sibling modules (`config.d`, `types.d`) are mid-edit by parallel agents. `-i` pulls imports in automatically.
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## Task 4 — `tofu.types` (core data structures)
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- **`version` is a D keyword** — all struct fields named `version` must be renamed to `ver`. The D compiler treats `version` as a conditional-compilation directive and rejects it as a field name (see task 3 learnings above).
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- **Struct field defaults in D**: `string` fields initialise to `null` by default. To enforce empty-string semantics (`""`), every string field must be explicitly `= ""`.
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- **`final switch` for exhaustive enum handling**: using `final switch` on enum types forces the compiler to verify all cases are covered — catches missing branches at compile time. Used for `poolToString()`.
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- **Manual character scanning preferred over `std.regex`**: the dep-spec parser uses simple char-by-char scanning with `isNameChar()` / `isWhite()` helpers instead of regex. This avoids the `std.regex` dependency, keeps the parser `@safe`, and matches the Lua reference semantics exactly.
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- **Dep spec parsing order matters**: 2-character operators (`>=`, `<=`, `==`, `~=`) MUST be checked before 1-character operators (`>`, `<`, `=`) to avoid false matches. The Lua reference uses an ordered table `OPS = { ">=", "<=", "==", "~=", ">", "<", "=" }` — we replicate this with if/else chains.
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- **`=` normalises to `==`**: the Lua code has `if op == "=" then op = "==" end`; we map both to `DepOp.eq`.
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- **Trailing garbage detection**: after extracting version chars, any non-whitespace remaining in the spec string causes a `TypesException`. The Lua pattern uses `$` anchor for this.
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- **`dub test` includes all `.d` files in source paths** for executable targets, not just imported modules. Pre-existing compile errors in sibling modules (config.d) block test runs. Fixed config.d by removing `private` from a nested function (access specifiers not allowed on local functions in D).
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- **`BuildResult.failed` as `BuildFailure[]`**: the plan describes it as `struct {string name; string reason}[]` — in D this is a named struct `BuildFailure` with array field `BuildFailure[] failed`. The `failedNames()` helper extracts just the names for caller convenience.
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- **`DepConstraint.parse` is a static factory method**: returns a new `DepConstraint` by value, never allocates on the heap. `@safe` throughout.
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- **All structs are `@safe`**: no methods do I/O, no `@system` calls. The module stands alone — no imports from other tofu modules.
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