Add strict2_parse to assign and capture tags

[aswamy]

Summary

Adds strict2_parse to the assign and capture tags so invalid variable names are rejected in strict2 mode.

Both tags previously used only regex (VariableSignature) to validate variable names across all parse modes. This allowed invalid identifiers like (a(b(c), [x.y], and a.b to be silently accepted.

assign:

• strict2_parse uses the regex to split on =, then validates the LHS with Parser#consume(:id) + consume(:end_of_string)
• RHS is delegated to Variable.new as before

capture:

• strict2_parse uses Parser#consume(:id) + consume(:end_of_string) to validate the variable name

Both tags now include ParserSwitching and dispatch through strict_parse_with_error_mode_fallback. Lax mode is unchanged.

Depends on: Shopify/liquid-rewriter-private#215 (rewriter changes)

Tophat

bundle install
bundle exec irb -r liquid

# Invalid names rejected in strict2
Liquid::Template.parse("{% assign (a(b(c) = 1234 %}", error_mode: :strict2)
# => Liquid::SyntaxError

Liquid::Template.parse("{% capture [x.y %}hello{% endcapture %}", error_mode: :strict2)
# => Liquid::SyntaxError

# Valid names still work
Liquid::Template.parse("{% assign my-var = 'hello' %}", error_mode: :strict2)
# => OK

# Lax mode unchanged
Liquid::Template.parse("{% assign (a(b(c) = 1234 %}", error_mode: :lax)
# => OK

🤖 Generated with Claude Code

[graygilmore]

This all seems reasonable!

[EvilGenius13]

I don't think you need the include here because Tag already has it.

[EvilGenius13]

Same here