452

[RAprogramm]

Closes #452

#[app_error(...)]-generated From conversions now attach the domain error as source instead of discarding it, and AppError forwards providers.

Codegen

• Struct with message: message computed from the value, then the value moves into the source slot; without message: bare error + source
• Enum: base error built per variant via match &value, single .with_source(value) after the match
• Generated impl requires Self: Error + Send + Sync + 'static (satisfied by the same derive; escape hatch below)
• New no_source flag restores the old drop-value behavior for non-Send/Sync domain types (all-or-nothing across enum variants, mixed use is a compile error)

Runtime

• impl Error for AppError gains cfg-gated provide: forwards the attached backtrace and delegates to the stored source — request_ref/request_value now reach #[provide] data through a converted AppError on toolchains with error_generic_member_access
• On stable, the source chain alone makes is/downcast_ref/downcast/chain/root_cause work through conversions

Tests & docs

7-test integration file (incl. chain traversal to root cause and a ProblemJson regression: source never serialized), provide-forwarding tests, updated trybuild pass cases + new no_source pass case with Rc fields, 10 new derive unit tests (expansion + parser). README conversion paragraph rewritten (was: 'the domain error is dropped'), derive docs, wiki pages in three languages updated. Full workspace suite, doctests (176), no_std build, clippy zero warnings (all targets), nightly fmt, readme_sync, benches — all green after rebase over #447/#445.

[codecov]

Codecov Report

❌ Patch coverage is 99.25373% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
masterror-derive/src/app_error_impl.rs	98.91%	1 Missing ⚠️

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