Stop mangling tagged templates and backquoted strings #7841
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Pull Request Overview
This PR fixes the compilation of tagged templates and backquoted strings in ReScript to preserve their original formatting in the generated JavaScript output. Previously, these were being mangled with unnecessary escape sequences.
- Adds support for
DBackQuotesdelimiter type to preserve template literal syntax - Updates the string constant representation to track delimiter information instead of just unicode flag
- Modifies the compiler pipeline to properly handle backquoted strings and tagged templates
Reviewed Changes
Copilot reviewed 46 out of 46 changed files in this pull request and generated 2 comments.
Show a summary per file
| File | Description |
|---|---|
| tests/tests/src/*.mjs | Test output files showing proper backquote preservation in generated JS |
| compiler/frontend/external_arg_spec.ml* | Adds DBackQuotes delimiter type |
| compiler/frontend/ast_utf8_string_interp.ml | Updates string interpolation handling for template literals |
| compiler/frontend/lam_constant.ml* | Changes Const_string to use delim field instead of unicode boolean |
| compiler/core/*.ml | Updates constant handling throughout compiler pipeline |
| compiler/core/js_dump.ml | Adds backquote output support in JS generation |
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| let is_template = | ||
| Ext_list.exists e.pexp_attributes (fun ({txt}, _) -> | ||
| match txt with | ||
| | "res.template" | "res.taggedTemplate" -> true | ||
| | _ -> false) |
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The template detection logic is duplicated in the transform_exp function but not in transform_pat. This inconsistency could lead to different behavior between expressions and patterns. Consider extracting this logic into a helper function or ensuring consistent template detection across both functions.
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this is because you can't have string interpolation in pattern matching.
| let is_unicode_string opt = Ext_string.equal opt Delim.escaped_j_delimiter | ||
| let is_unicode_string opt = | ||
| Ext_string.equal opt Delim.escaped_j_delimiter | ||
| || Ext_string.equal opt Delim.escaped_back_quote_delimiter | ||
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| let is_unescaped s = Ext_string.equal s Delim.unescaped_js_delimiter |
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The is_unescaped function only checks for the unescaped_js_delimiter but doesn't account for the new backquote delimiter. This could lead to inconsistent behavior when processing unescaped strings with different delimiters.
| let is_unescaped s = Ext_string.equal s Delim.unescaped_js_delimiter | |
| let is_unescaped s = | |
| Ext_string.equal s Delim.unescaped_js_delimiter | |
| || Ext_string.equal s Delim.escaped_back_quote_delimiter |
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Fixes #7777, #7196.
With this PR
generates
It used to generate
Backquoted strings are now compiled as backquoted strings in JS, but they are still concatenated with
+when there are interpolations, this could be improved in a subsequent PR (for v12.1?).