fix: support else if conditional attributes

[akfaew]

Summary

Adds first-class parser and AST support for else if branches in conditional attributes.

Previously, conditional attributes only modeled if and final else branches, so formatting an attribute-level conditional with else if could serialize poorly as a split else plus nested if. This updates conditional attributes to mirror normal templ if handling more closely.

Changes

• Add ConditionalElseIfAttribute and ConditionalAttribute.ElseIfs.
• Parse zero or more } else if ... { ... } conditional attribute branches before an optional final else.
• Update conditional attribute formatting to emit } else if ... { on one line.
• Update copy, visitor traversal, and generator handling for conditional attribute else if branches.
• Add tests for:
  • formatter round-trip with else if
  • multiple else if branches
  • AST shape
  • generator output
  • visitor-based attribute formatting

Testing

go test ./parser/v2 -run 'TestElementFormatting|TestConditionalAttributeElseIfsParseAsBranches'
go test ./generator -run TestWriteConditionalAttributeElseIf
go test ./internal/format -run TestAttributes
go test ./parser/v2 ./parser/v2/visitor ./generator ./cmd/templ/fmtcmd ./internal/format
git diff --check

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Adds support for else if branches in conditional attributes across parsing, AST representation, formatting, visiting, and code generation.

Changes:

• Extend ConditionalAttribute AST to include ElseIfs branches and implement deep-copy support.
• Update parser/visitor/generator to traverse and emit else if blocks.
• Add tests covering parsing, formatting, and generator output for conditional attribute else if branches.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
parser/v2/visitor/visitor.go	Ensures else if branches are visited so downstream processing sees all attributes.
parser/v2/types.go	Extends the AST with ElseIfs and updates serialization/copy helpers.
parser/v2/elementparser_test.go	Adds formatting + parsing tests validating else if branch handling.
parser/v2/conditionalattributeparser.go	Implements parsing of else if branches for conditional attributes.
internal/format/attributes_test.go	Updates formatting tests to include an ElseIfs branch.
generator/generator_test.go	Adds a generator regression test ensuring else if is emitted.
generator/generator.go	Updates generation and attribute analysis to include else if branches.