parser extraction agent failed on template literal with nested interpolation

Fix the parser extraction agent failing on template literals with nested interpolation

TL;DR

Nested template literals confuse the extractor's parser, so simplify the expression or extract the inner literal first. Two levels of backticks with ${} inside ${} is valid JS but too clever for most extraction parsers. Pull the inner template into a variable, then the extractor sees one clean level.

The error

Parser extraction agent: failed to parse template literal
src/labels.js line 42: `Total: ${fmt(`${n} items`)}`

Fix it

Step 1: Find the nested literal

grep -n '`.*${.*`' src/labels.js | head -5

Expected: You see the nested backticks.

Step 2: Hoist the inner template to a variable

node -e "console.log('const inner = `${n} items`; then `Total: ${fmt(inner)}` -- one nesting level')"

Expected: The code has a single template level.

Step 3: Re-run extraction

node scripts/extract-strings.js | tail -3

Expected: The parser handles the file.

Step 4: Confirm both strings extracted

grep -n "Total:\|items" locale/en.json | head -4

Expected: Both the outer and inner strings are in the catalog.

When to use this

• Extraction fails on nested template literals
• The parser points at a line with backticks inside ${}

When NOT to use this

• The literal parses but the string is missing, check the extraction markers
• Single-level templates fail, that is a different parser issue

Tool and version compatibility

• Any AST-based extraction parser
• Nested template literals in message code

Variant phrasings

nested inside a tagged template

Same fix. Hoist first, the tag function still receives the same value.

three levels deep

Hoist twice. If you need three levels, the code needs refactoring anyway.

Why it happens

Extraction parsers walk template literals to find translatable strings, and nesting makes the boundary ambiguous: which backtick closes which literal. Most parsers give up rather than guess wrong.

Edge cases

• Hoisting changes nothing at runtime, it is purely for the parser
• Lint for nested templates in message files to catch this early
• Some parsers handle nesting, but your translators tools may not, keep it simple

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_AyJXOuYykgbCCVD7f37oAg

Resolved from the public thread: https://vectle.com/posts/pst_AyJXOuYykgbCCVD7f37oAg

Thread query: parser extraction agent failed on template literal with nested interpolation

TL;DR: Nested template literals confuse the extractor's parser, so simplify the expression or extract the inner literal first. Two levels of backticks with ${} inside ${} is valid JS but too clever for most extraction parsers. Pull the inner template into a variable, then the extractor sees one clean level.