fix(markdown-template): preserve parent scope in conditional and optional blocks

[mttrbrts]

Ports the fix from #647 by @yashhzd to the TypeScript TypeVisitor.ts introduced in #677. #647 can't merge now because it edits the removed src/TypeVisitor.js and lib/TypeVisitor.js. The commit credits @yashhzd as co-author.

Fixes accordproject/template-playground#2 (Cannot use variables inside an #if block)

Problem

TypeVisitor set the scope of an {{#if}} body, and of a primitive {{#optional}} body, to the guarded field itself. A field has no properties, so any named variable inside the block failed type-checking:

{{#if age}}You are {{age}}{{/if}}           -> Unknown property: age
{{#if age}}Hi {{name}}{{/if}}               -> Unknown property: name
{{#optional age}}Hi {{name}}{{/optional}}   -> Unknown property: name

The {{else}} branches (whenFalse and whenNone) were visited with model: null, so every variable in them failed as well.

Changes

All changes are in packages/markdown-template/src/TypeVisitor.ts.

• ConditionalDefinition: both branches keep the parent model.
• OptionalDefinition:
  • A primitive optional keeps the parent model in both branches.
  • A complex optional still scopes whenSome to the nested class.
• {{this}}: a new thisProperty parameter carries the guarded field. {{this}} inside {{#if age}} or {{#optional age}} therefore still resolves to Integer, as it does today.

One difference from #647: #647 dropped the {{this}} handling for #if, and this PR keeps it.

Tests

New Jest cases in src/TemplateMarkTransformer.test.ts cover:

• named and sibling variables in #if, #optional and their {{else}} branches
• unknown variables being rejected in each of those positions
• element types of variables inside #if
• {{this}} in #if and in a primitive #optional
• a complex #optional still scoping to the nested class

Results:

• With the TypeVisitor.ts change reverted, 8 of the new tests fail.
• markdown-template passes: 26 tests.
• markdown-transform passes: 31 tests.
• tsc --noEmit is clean.
• ESLint reports no errors; its warnings were already there.

🤖 Generated with Claude Code

[coveralls]

Coverage Report for CI Build 38133185014

Coverage increased (+3.9%) to 82.866%

Details

• Coverage increased (+3.9%) from the base build.
• Patch coverage: 3 of 3 lines across 1 file are fully covered (100%).
• No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

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