[BUGFIX] Invoke argument-less helpers in attribute position in strict mode

[NullVoxPopuli]

Fixes #21040

Supersedes #21508

• see here for history and context

Blocked on:

• Strict mode: helpers inside attribute concats are not auto-invoked #21040 (comment)
• added Needs RFC label, for lack of a better label -- though I argue this one particular feature does not need an RFC

Context:

• https://github.com/emberjs/rfcs/blob/508ac9b95bf2a4b397bf72b8e51d981c14c42535/text/0496-handlebars-strict-mode.md#3-no-implicit-invocation-of-argument-less-helpers
  • The RFC only stated what to do in argument-position, which is correct, and we don't want to change

[github-actions]

📊 Size report

Tarball size — 1.2 MB → 1.2 MB

dist/dev   0.06%↑

File	Before (Size / Brotli)	After (Size / Brotli)
./packages/shared-chunks/index-{hash}.js	62.6 kB / 12.5 kB	2%↑63.8 kB / 2%↑12.8 kB
Total (Includes all files)	2.1 MB / 498 kB	0.06%↑2.1 MB / 0.06%↑498.3 kB

---

dist/prod   0.06%↑

File	Before (Size / Brotli)	After (Size / Brotli)
./packages/shared-chunks/index-{hash}.js	59.8 kB / 12.1 kB	2%↑61 kB / 2%↑12.4 kB
Total (Includes all files)	1.9 MB / 455.4 kB	0.06%↑1.9 MB / 0.06%↑455.7 kB

---

smoke-tests/v2-app-template/dist   0.05%↑

File	Before (Size / Brotli)	After (Size / Brotli)
./assets/api-{hash}.js	287.9 kB / 77.5 kB	0.06%↑288.1 kB / 0.06%↑77.5 kB
Total (Includes all files)	351.2 kB / 97.8 kB	0.05%↑351.4 kB / 0.03%↑97.8 kB

---

smoke-tests/v2-app-hello-world-template/dist   0.1%↑

File	Before (Size / Brotli)	After (Size / Brotli)
./assets/main-{hash}.js	132.2 kB / 36.9 kB	0.1%↑132.4 kB / 0.1%↑36.9 kB
Total (Includes all files)	132.6 kB / 37 kB	0.1%↑132.7 kB / 0.2%↑37.1 kB

_{🤖 This report was automatically generated by wyvox/pkg-size}

[Copilot]

Pull request overview

This PR fixes a strict-mode inconsistency where argument-less helpers (and plain functions with helper managers) used in attribute value / attribute interpolation were not implicitly invoked, causing stringification (e.g. Function.prototype.toString) instead of producing the helper’s return value.

Changes:

• Introduces DynamicAttrValue() to compile strict-mode attribute-position expressions, invoking bare lexical helpers/functions (and rejecting components) while preserving value semantics otherwise.
• Routes dynamic element attributes, component invocation attributes (...attributes passthrough), and Concat parts through DynamicAttrValue() instead of the generic expr() path.
• Adds a new strict-mode integration test suite covering helper/function invocation in attribute position (including interpolation, trusting attrs, updates, and error cases).

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
packages/@glimmer/opcode-compiler/lib/syntax/statements.ts	Uses DynamicAttrValue() for dynamic attribute compilation paths (plain + trusting, element + component attrs).
packages/@glimmer/opcode-compiler/lib/syntax/expressions.ts	Compiles Concat parts via DynamicAttrValue() to ensure attribute interpolations invoke bare lexical helpers/functions correctly.
packages/@glimmer/opcode-compiler/lib/opcode-builder/helpers/vm.ts	Adds DynamicAttrValue() helper implementing compile-time OptionalComponentOrHelper resolution for bare lexical symbols in attribute-position.
packages/@glimmer-workspace/integration-tests/test/strict-mode-test.ts	Adds strict mode: attribute position test suite validating the intended behavior and guarding regressions.

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[NullVoxPopuli]

That's a summary, not a review. Silly copilot

[kategengler]

Making it a draft since it needs an RFC