Several related booleans represent richer state

Timing: Follow-up after trial/3 merges into main; defer implementation until then.

Review baseline: Local trial/3 at a094418baf6388e3eeca23821df481a7f0a8751c. This branch is not yet on the remote. Source locations below refer to that snapshot and should be rechecked after merge.

Problem

account_keys accepts separate object, array, added, and removed booleans. Valid combinations depend on caller knowledge, while the signature permits contradictory combinations. No incorrect current call was established; this is a maintainability and invariant-expression concern.

Evidence

crates/lib/src/data/mutation.rs:190-198: call assembled from several state flags.
crates/lib/src/data/mutation.rs:231-288: branching over four booleans and container-transition state.

Acceptance criteria

Express meaningful container shape and mutation outcome through enums or another representation that makes invalid combinations difficult to construct.
Preserve accounting, overflow/error precedence, atomic mutation guarantees, and dense/sparse conversion behavior.
Verify representative insert/remove/no-change and object/array transition cases.
Keep genuinely independent capability flags as booleans; do not mechanically replace every collection of flags.

Code examples and suggested direction

Possible private state model:

#[derive(Clone, Copy, Debug)]
enum ContainerBefore {
    Missing,
    Object,
    Array,
}

#[derive(Clone, Copy, Debug)]
enum MembershipChange {
    Unchanged,
    Added,
    Removed,
}

Then replace the boolean bundle with meaningful inputs:

fn account_keys(
    before: ContainerBefore,
    membership: MembershipChange,
    final_length: usize,
    step: &Step,
    change: &mut Change,
) -> Result<()> {
    // Port the existing accounting rules through an exhaustive match.
    // The body must be implemented from the current decision table.
}

The signature is a design sketch, not complete compilable replacement code. Scalar traversal must still fail before accounting.

Suggested investigation and fix notes

Deferred until trial/3 is merged into main. Recheck the merged source and tests first. The snippets are examples/proposals, not an approved patch or a change to frozen contracts.

Derive a decision table from Preparation::inspect before replacing flags: existing object/array/missing intermediate; membership added/removed/unchanged; final object/array; leaf versus ancestor; root versus nested container.
Confirm what Unchanged means: membership can be unchanged even when a payload is replaced. Preserve separate payload accounting.
Construct the enums where facts become known and pass them into account_keys. Avoid an enum-to-booleans-to-enum round trip or new validation that changes existing error precedence.
Port rules one transition at a time. In particular, dense object→array removes numeric-key bytes; array→sparse object adds retained numeric-key bytes; missing removal must not create containers.
Retain read-only planning followed by commit. Overflow/limit errors must leave both tree and cached totals unchanged.

Observable regression example:

use stackpress_lib::{Nest, Result};

fn sparse_transition() -> Result<()> {
    let mut data = Nest::new();
    data.set_path("items.0", "a")?;
    data.set_path("items.1", "b")?;
    assert!(data.path("items").unwrap().as_array().is_some());
    data.remove_path("items.0")?;
    assert!(data.path("items.0").is_none());
    assert_eq!(data.path_as::<String>("items.1")?, Some("b".into()));
    Ok(())
}

Add boundary/accounting cases to existing data_contracts; run cargo test -p stackpress-lib --test data_contracts --locked. Independent capability booleans elsewhere are outside this focused refactor.

Implementation workflow: After the merge, follow .agents/workflows/rust-programming.md: prove the affected behavior, complete the three test-verified review rounds, and record relevant formatting/lints/docs, feature/platform scope, and applicable development coverage. Preserve unrelated changes.

Fixed on trial/3 in 644795f (merged as 64a5b70, task 00010 lane 1; not yet on main, so leaving open).

Mutation accounting now uses private container-shape and membership-change enums instead of four related booleans; checked-arithmetic order, atomic mutation plans and dense/sparse behavior are unchanged (existing budget-oracle tests rerun throughout).

Coordinator-verified: fmt, Clippy -D warnings, Rustdoc -D warnings, cargo +1.96.0 check, 454 workspace tests, 856 doctests pass; lib production coverage 93.64%.

Fix owner review issues #11, #1, #2, #5 and lib parts of #4, #7 (task…

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Several related booleans represent richer state #5

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Several related booleans represent richer state #5

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cblanquera commented on Oct 26, 2026

Suggested investigation and fix notes

cblanquera commented on Oct 26, 2026

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