Add support for map type by yordis · Pull Request #12216 · bytecodealliance/wasmtime

yordis · 2025-12-23T21:42:43Z

Context

This is adding support for map based on WebAssembly/component-model#554

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github-actions · 2025-12-23T23:46:00Z

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github-actions · 2025-12-24T01:06:25Z

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alexcrichton · 2026-01-07T18:09:25Z

On a skim this looks like it's all in the right direction, thanks! As as a heads up the wasm-tools deps will be updated in #12254 which'll avoid the need for git deps. I'll take a closer look once this is further along in CI passing tests

github-actions · 2026-01-08T11:46:55Z

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.gitignore

alexcrichton

This is looking quite good to me, thanks for the thorough tests!

I haven't scrutinized the trampoline generation nor the lifting/lowering yet, but I can do that once the tests added here are passing (the #[ignore] ones at least).

If you can one thing I'd also recommend is modeling as many tests as possible as a *.wast test since that's generally the easiest to run and share (albeit difficult to write and debug)

crates/test-util/src/component.rs

crates/test-util/src/component_fuzz.rs

tests/misc_testsuite/component-model/types.wast

.gitignore

alexcrichton

Mostly some thoughts about deduplication/sharing of the gnarliest bits below --

crates/environ/src/fact/trampoline.rs

crates/wasmtime/src/runtime/component/func/typed.rs

crates/wasmtime/src/runtime/component/values.rs

tests/all/component_model/func.rs

yordis · 2026-02-27T06:04:56Z

@alexcrichton addressed the comments, about the sharing stuff, feedback welcome there, I am not sure if it is the best way or not; not sure what you had in mind

This commit introduces support for HashMap<K, V> in the component model, allowing maps to be represented as list<tuple<K, V>> in the canonical ABI. It includes implementations for the ComponentType, Lower, and Lift traits for HashMap, enabling type checking, lowering to flat representations, and lifting from memory. Additionally, the maximum depth for type generation in the fuzzing utility is updated to accommodate the new map type.

This commit removes the previous wasm features configuration and adds new functions for creating a map-configured engine. The `map_config` and `map_engine` functions are introduced to facilitate the use of the component model with maps in tests, ensuring that the engine is properly configured for map types in the component model.

…existing tests This commit introduces a new WAST test file specifically for testing various map types in the component model. Additionally, it removes the redundant map type definitions from the existing types.wast file to streamline the test suite.

…eturn with call

…n typed.rs

…ved iteration and memory management. Introduce new implementations for ComponentType, Lower, and Lift traits for std::collections::HashMap, enhancing support for map types in the component model.

The translate_map function had two categories of bugs preventing map adapter trampolines from working: 1. Wasm stack discipline: local_set_new_tmp emits LocalSet which pops from the stack, but was called when the stack was empty (to "pre-allocate" locals). Fixed by computing values first, then calling local_set_new_tmp to consume them—matching translate_list's pattern. Also removed an erroneous LocalTee that left an orphan value on the stack. Affected: src_byte_len, dst_byte_len, cur_src_ptr, cur_dst_ptr. 2. Pointer advancement: after value translation, the pointer still points at the value start. The code only advanced by trailing padding instead of value_size + trailing_padding, causing every loop iteration to re-read the same memory. Also fixes entry layout to use proper record alignment rules (entry align = max(key_align, value_align), value at aligned offset).

Val::Map already holds Vec<(Val, Val)> which derefs to &[(Val, Val)], matching lower_map's signature directly. The intermediate Vec allocation and deep clone of every key/value pair was redundant.

…er_map_to_memory helpers

- component_fuzz: use saturating_sub in generate_hashable_key to prevent underflow when fuel is 0 and Enum variant is chosen - typed: remove incorrect ? operators in lift_map for hashbrown::HashMap (with_capacity and insert don't return Result)

Compute map entry ABI and value offsets once during type building, and reuse that metadata in runtime map lift/lower paths instead of recalculating tuple layout at each call site.

Bundle map lift/lower layout and type metadata into a small MapAbi32 helper so map helper calls stay concise without changing behavior.

…rary_val The fuzzer's component_api oracle was generating map types but the engine didn't have the map feature enabled, and arbitrary_val had no arm for Type::Map. Enable component_model_map in the store helper (matching how component_model_async is forced on) and implement arbitrary value generation for map types.

In reading over bytecodealliance#12216 I found a few related but also somewhat orthogonal refactors that I wanted to implement, and thus this commit. Changes here are: * Handling pointer pairs for lists/maps/strings is now more uniform with a single set of functions doing the lift/lower to flat/memory. Less "FIXME 4311" spread throughout effectively. * Conditional defines and organization of the `HashMap`-related impls were tweaked, for example impls on `HashMap` are now unconditional as well as `TryHashMap`. Some internals were refactored to in theory reduce complexity, but this is also subjective. * Lifting a `map<K, V>` now consumes fuel, a recent change, to ensure that resource exhaustion in the host is limited.

yordis force-pushed the yordis/feat-map-support branch 3 times, most recently from 6b6f675 to cd2282b Compare December 23, 2025 21:53

yordis force-pushed the yordis/feat-map-support branch 5 times, most recently from db45a3a to 83dd7a7 Compare January 8, 2026 10:17

github-actions bot added the fuzzing Issues related to our fuzzing infrastructure label Jan 8, 2026

yordis force-pushed the yordis/feat-map-support branch from 83dd7a7 to b9ca740 Compare January 8, 2026 19:19

yordis commented Jan 16, 2026

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alexcrichton reviewed Jan 20, 2026

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crates/test-util/src/component.rs Outdated Show resolved Hide resolved

crates/test-util/src/component_fuzz.rs Outdated Show resolved Hide resolved

tests/misc_testsuite/component-model/types.wast Outdated Show resolved Hide resolved

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yordis force-pushed the yordis/feat-map-support branch from 301e19b to d291adf Compare February 6, 2026 06:26

yordis requested a review from alexcrichton February 10, 2026 20:12

yordis force-pushed the yordis/feat-map-support branch from ddac63a to b6376cb Compare February 16, 2026 23:06

yordis marked this pull request as ready for review February 16, 2026 23:07

yordis requested review from a team as code owners February 16, 2026 23:07

alexcrichton reviewed Feb 20, 2026

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yordis force-pushed the yordis/feat-map-support branch from b6376cb to e644b8b Compare February 27, 2026 01:21

yordis added 20 commits March 9, 2026 19:07

Update component fuzzing and dynamic tests to replace call_and_post_r…

a219108

…eturn with call

Format code

59f95f3

Refactor HashMap usage in typed.rs to use wasmtime_environ collections

33891f4

Fix HashMap initialization and insertion to handle potential errors i…

d02a7f8

…n typed.rs

Refactor HashMap handling in typed.rs to use lower_map_iter for impro…

a40bb64

…ved iteration and memory management. Introduce new implementations for ComponentType, Lower, and Lift traits for std::collections::HashMap, enhancing support for map types in the component model.

Refactor map entry layout calculations to use canonical ABI

db1f816

Remove unnecessary clone of map pairs during lowering

504c7eb

Val::Map already holds Vec<(Val, Val)> which derefs to &[(Val, Val)], matching lower_map's signature directly. The intermediate Vec allocation and deep clone of every key/value pair was redundant.

Deduplicate map lift logic between HashMap implementations

1097cda

Deduplicate list and map sequence translation scaffolding

cd97d70

Fix cargo fmt formatting issues

d48daf5

Deduplicate map typecheck logic

24c75e0

Deduplicate map lowering with linear_lower_map_to_flat and linear_low…

9f860ff

…er_map_to_memory helpers

Clean up lift_try_map: use drop, move TryHashMap import to module scope

1d6ca26

Store map tuple layout in TypeMap

12ed288

Compute map entry ABI and value offsets once during type building, and reuse that metadata in runtime map lift/lower paths instead of recalculating tuple layout at each call site.

Refactor map ABI argument passing

b94eac8

Bundle map lift/lower layout and type metadata into a small MapAbi32 helper so map helper calls stay concise without changing behavior.

yordis force-pushed the yordis/feat-map-support branch 2 times, most recently from 1802a87 to 2898eee Compare March 9, 2026 23:15

yordis force-pushed the yordis/feat-map-support branch from 2898eee to 36008b6 Compare March 9, 2026 23:18

alexcrichton enabled auto-merge March 9, 2026 23:23

alexcrichton added this pull request to the merge queue Mar 9, 2026

Merged via the queue into bytecodealliance:main with commit 1b59b57 Mar 9, 2026
49 checks passed

alexcrichton mentioned this pull request Mar 10, 2026

Lift/lower refactors inspired by map<K, V> #12753

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Add support for map type#12216

Add support for map type#12216
alexcrichton merged 26 commits intobytecodealliance:mainfrom
yordis:yordis/feat-map-support

yordis commented Dec 23, 2025 •

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yordis commented Dec 23, 2025 •

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