Apply Hash conditions to scoped existence probes

[bunnykong]

Scoped Relation#exists? calls apply Hash conditions through the existing predicate builder, preserving the scope and SELECT 1 … LIMIT 1 probe.

scope = Widget.where(owner_id: 1)
scope.exists?(number: 7)
# With a matching row: false before, true after.

On main b28b17b68d1fc879c506765cdc18142518544494, the runtime treats the entire Hash as a primary-key value. Rails 8.1.4 instead applies Hash conditions to the existing relation. Recognized static chains already lower correctly; this change repairs calls that reach Relation#exists? at runtime.

Hash inputs use hash_conditions, and empty Hashes add no predicate. Relations take ownership of shared query lists before adding a temporary predicate. An ensure restores temporary predicates after successful or failed SQL execution, while retaining loaded records. Non-Hash inputs retain their existing SQL construction. The RBS signature adds the supported Hash and String forms.

The shared column_predicate validates each composed Hash key once with sql_ident, also covering the pre-existing where(hash) route. Ordinary and table.column keys retain their behavior; malformed keys raise ArgumentError before SQL composition because identifiers are bare, whereas Rails quotes them and raises ActiveRecord::StatementInvalid at execution. hash_where_identifiers_run_on_* and hash_exists_identifiers_run_on_* cover malformed top-level and nested keys on Ruby and native Spinel, proving zero queries, unchanged scopes and no out-of-scope matches. Value escaping stays unchanged.

The two existing Hash-condition regressions fail on main with hash probe misses its row and pass with the change, with zero analysis or emission errors. The assertions also pass against Rails 8.1.4. Coverage includes matching and missing rows, scope isolation, compound conditions, NULL, IN, empty arrays inside Hashes, string keys, empty Hashes, scalar IDs, zero limits, loaded records and cleanup after a database error.

Validation uses macOS arm64, CRuby 3.4.9 for Roundhouse’s suites on the pinned 3.4 line, CRuby 4.0.7 for emitted apps, Rails parity probes and native Spinel reference outputs, Rust 1.98.1 and Spinel e5e8f794c. The branch is based on main b28b17b6:

• Ruby/native regressions pass 6/6: the two existing Hash-condition tests and four identifier tests. All six fail on main at their behavior assertions. Native execution with emitted RBS sidecars passes 3/3.
• cargo test --locked --lib: 1,025 tests pass; 1 is ignored.
• Runtime typing passes 5/5 with the unchanged 299-site concrete-typing ceiling. Relation runtime passes 1/1; counted terminals pass 6/6.
• The framework Ruby source gate passes 1/1, the emitted framework suite passes 12/12, and lowered Ruby emission passes 109/109. Bind planning: 5 tests pass; 5 are ignored. These focused gates total 127 passing tests and 5 ignored tests, plus 12 emitted framework tests.
• The complete emit_and_run selection has 228 passing tests and 16 ignored tests on each of CRuby 3.4.9 and 4.0.7.
• The CI planner passes 53/53. git diff --check passes.

The complete default suite starts with a fresh Cargo target directory on CRuby 3.4.9: 4,253 tests pass, 172 are ignored and three fail. All three failures reproduce on main b28b17b6: automatic loading of the Rails Minitest plugin collides with the runtime Logger shim, ruby-vips is missing, and Bash 3.2 lacks mapfile for the Campfire workflow test. Disabling external Minitest plugins with MT_NO_PLUGINS=1 and installing ruby-vips makes the affected source and vips checks pass; the Bash prerequisite remains. The 12 framework checks pass with the scaffold’s frozen bundle dependencies installed.

Emission comparison with the default policy covers seven fixture inputs and all 15 targets: 105 combinations and 10,807 files. Exactly 42 files differ: the relation runtime, including the identifier guard, and its RBS copies in Ruby, JRuby and Spinel. The other 10,765 files and all diagnostics are identical. Generated application queries retain their previous shapes.

This change repairs dispatch for Hash conditions. Existing differences from Rails remain for explicit nil/false, top-level SQL arrays, model-level runtime exists?, mixed-NULL IN lists and integer serialization. A 116-call Rails oracle distinguishes these boundaries; the change makes no broader casting or finder-support claim.

#437 changes the RBS inference probe, and #438 changes primary-key find casting. Prepared-read changes #403 (merged), #404 and #405 share runtime files but change separate methods and bind planning. None implements this relation Hash fallback. #327 addresses LIKE value escaping, without the shared Hash identifier guard.

Part of the Conduit worklist: bunnykong#1

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Summary by CodeRabbit

• New Features
  • exists? accepts hash conditions to check for records matching attribute values. Conditions support scoped relations, compound predicates, arrays, NULL values, empty conditions, and string or symbol keys.
  • Integer and string values continue to check against the model’s primary key.
• Bug Fixes
  • Temporary conditions are cleared after a check, including when it fails, leaving the relation usable.
  • Malformed SQL identifiers are rejected before a query is executed, without changing the relation’s scope.

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📒 Files selected for processing (3)

• runtime/ruby/active_record/relation.rb
• runtime/ruby/active_record/relation.rbs
• tests/emit_and_run.rs

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📝 Walkthrough

Walkthrough

Relation#exists? accepts hash conditions and builds predicates with the shared predicate builder. Scalar values retain primary-key matching. The method removes its temporary predicate after the probe, including when the probe raises. The signature and regression tests cover the expanded argument forms and SQL identifier validation.

Changes

Relation existence conditions

Layer / File(s)	Summary
Build existence predicates runtime/ruby/active_record/relation.rb, runtime/ruby/active_record/relation.rbs	Relation#exists? uses the shared predicate builder for hash conditions and retains primary-key matching for scalar values. Its signature accepts integer, string, hash, and nil arguments. column_predicate validates column identifiers.
Verify existence conditions tests/emit_and_run.rs, tests/emit_and_run/integer_query_exists.rs	The registered tests cover hash-condition forms, relation state, scalar probes, and SQL identifier validation through where and exists?.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

Suggested reviewers: thomasklemm

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Merge Risk

Merge Risk: ⚪ Minimal · up to 06f95

Hash-based existence probes are supported while preserving relation scope, and malformed column identifiers are rejected before SQL executes. No actionable merge-blocking risk remains.

Security Architecture Review

Security architecture risk: 🔵 Low · up to 06f95

The expanded existence probe preserves existing query scopes, validates condition identifiers, and improves cleanup after query failures. No authorization bypass was demonstrated. Application-level input handling and concurrent use of shared relations remain unverified.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — A caller can now select valid non-primary-key predicates for a Boolean probe over the relation's existing query scope. This is a contract expansion, not an authorization mechanism. Effective tenant, asset, and data-store exposure depends on how applications construct the relation and supply conditions; those callers are not established by the supplied evidence.

Trust Boundaries and Controls

• observed — The new Hash route separates identifier validation from value handling. Scalar and array values use existing adapter escaping, nil becomes IS NULL, and Relation values use the existing subquery renderer. The inspected SQLite adapter delegates value escaping to Db and executes the composed query through prepared-statement operations; the PR does not replace these controls.

Resilience and Maintainability Implications

• inferred — Cleanup still relies on removing the WHERE-list tail, so isolation is established for serial execution and spawned branches, not arbitrary same-instance interleaving. This mechanism predates the PR's Hash support. The documented model is a fresh relation per linear chain, and the inspected adapter has no explicit Relation callback. Concurrent sharing or custom-adapter reentry remains unverified rather than a demonstrated PR-introduced security concern.

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🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 78.57% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 14 functions across 3 files. (1 skipped: …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely identifies the main change: applying Hash conditions to scoped existence probes.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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Full details: Docstring Coverage

Explanation

Docstring coverage is 78.57% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 14 functions across 3 files. (1 skipped: 1 unsupported.)

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Inline comments:
Review comments at @runtime/ruby/active_record/relation.rb:
- Line 1310: Update `column_predicate` to validate the composed identifier with
`sql_ident` before interpolating it into SQL, covering both top-level and nested
keys passed through `hash_conditions`. Preserve the existing qualification and
predicate behavior for valid identifiers.

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📥 Commits

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📒 Files selected for processing (4)

• runtime/ruby/active_record/relation.rb
• runtime/ruby/active_record/relation.rbs
• tests/emit_and_run.rs
• tests/emit_and_run/integer_query_exists.rs

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[bunnykong]

Updated by merging main, without rewriting the branch. The October 7 unit (2) failure (lowered_controller_bodies_carry_no_synthetic_spans) came from main at the time: it fails on main 8f1940f2 alone, and #573 has since fixed it. With main merged, that test, the Hash regressions and the full default suite pass locally.