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[js-api] Allow a missing importObject for builtin imports - #2264
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Fixes WebAssembly#2102. read the imports threw TypeError whenever module_imports was non-empty and importObject was missing. A module whose imports are all satisfied by an enabled builtin, or by the imported string constants module, does not read importObject. Throw only if importObject is missing and some import is not supplied by those sources. Do that before allocating builtin instances.
Ms2ger
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Oct 5, 2026
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| 1. If |builtinOrStringImports|[|moduleName|] [=map/exists=], | ||
| 1. Let |o| be |builtinOrStringImports|[|moduleName|]. | ||
| 1. If |o| [=is not an Object=] or if [=?=] [$HasProperty$](|o|, |componentName|) is false, | ||
| 1. Set |o| to [=?=] [$Get$](|importObject|, |moduleName|). | ||
| 1. Else, | ||
| 1. Let |o| be [=?=] [$Get$](|importObject|, |moduleName|). |
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A quick read does not convince me that we'll never call Get with a missing argument. This needs at least a note to explain the invariant that prevents that.
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If importObject is missing, the opening check throws unless every import is an enabled builtin or an imported string constant. Those are own properties of builtinOrStringImports, so these Gets are not reached. Noted that after the algorithm, and asserted it before each call.
Get requires an Object. importObject can be missing when every import is an enabled builtin or an imported string constant, but those names are own properties of builtinOrStringImports, so the fallback Gets are not reached. Assert that before each fallback Get, and note it with the other notes on this algorithm.
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Fixes #2102.
read the importsthrew aTypeErrorwhenevermodule_importswas non-empty andimportObjectwas missing. That includes a module whose imports are allwasm:js-stringbuiltins, or all imported string constants. Those imports are supplied by the host. Chrome instantiates them with no import object.The check now runs only when
importObjectis missing, and it throws only if some import is not supplied by an enabled builtin or by the imported string constants module. It runs before builtin instances are allocated.A user import, an unknown name under
wasm:js-string, and a builtin mixed with a user import still throwTypeError. OmittingimportObjectand passingundefinedare the same.