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This pull request updates `add_expression_block` in the `Herb::Engine` to delegate to `add_expression` instead of dispatching directly to block result methods. This makes `Herb::Engine` a true drop-in replacement for `Erubi::Engine` when subclassed. Previously, subclasses that overrode `add_expression` (like ActionView's Erubi handler does) would not have their override apply to block expressions, because `add_expression_block` bypassed `add_expression` entirely. This meant subclasses also had to override `add_expression_block` and `add_expression_block_end` to handle blocks correctly. This pattern led to bugs like unmatched closing parentheses. Now, `add_expression_block` sets an `expression_block?` flag and delegates to `add_expression`. The default `add_expression` checks this flag to route to the appropriate block result methods, preserving the correct `<< (code do ... end)` output for standalone usage. A new `@_expression_block_open_paren` flag tracks whether the opening method added a parenthesis, so `add_expression_block_end` knows whether to close with `)` or just emit `end` as regular code. When no methods are overridden, the default `add_expression` routes block expressions to the existing `add_expression_block_result` methods, preserving Herb's smart block handling with proper parenthesization. When a subclass overrides only `add_expression`, the same pattern ActionView uses with Erubi, block expressions now flow through that override automatically. The `expression_block?` predicate lets the subclass distinguish blocks from regular expressions without relying on a `BLOCK_EXPR` regex, since the parser already knows. When a subclass overrides `add_expression_block` directly, that override takes precedence and the delegation never happens. Related marcoroth/reactionview#83 Related marcoroth/reactionview#84
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https://github.com/marcoroth/herb/releases/tag/v0.9.0
https://github.com/marcoroth/herb/releases/tag/v0.9.1
https://herb-tools.dev/blog/whats-new-in-herb-v0-9