codeconsole opened a new pull request, #16144:
URL: https://github.com/apache/grails-core/pull/16144
### Summary
A backslash immediately before a GSP expression now escapes it: `\${...}`
renders a literal `${...}` with the backslash removed, instead of the
expression being evaluated on the server.
GSP previously had no escape syntax at all — `\${x}` rendered a stray `\`
followed by the evaluated expression. The motivating case is JavaScript
template literals, whose interpolation placeholders share the `${}` syntax and
are today either evaluated against the page binding (an unbound name silently
renders as empty) or blow up the whole page render:
```html
<script>
const name = 'Grails';
console.log(`Hello \${name}`);
</script>
```
The browser now receives the template literal with its `${name}` placeholder
intact, to be interpolated by JavaScript.
### Implementation
Escaping is resolved entirely at parse time, in two small pieces:
- `GroovyPageScanner` no longer starts an expression token when the `${` is
immediately preceded by a backslash in template text — the sequence stays in
the surrounding HTML token.
- `GroovyPageParser.html()` rewrites `\${` to `${` when writing the HTML
token out.
Because this happens before code generation, behavior is identical in
development, production, and `compileStatic` modes, and escaped text is
invisible to static type checking — an escaped `${undeclaredName}` under `<%@
page compileStatic="true" %>` neither fails compilation nor evaluates (covered
by a new test in `GspCompileStaticSpec`).
### Semantics
- Only the backslash performing the escape is removed: `\\${x}` renders
`\${x}`.
- Each expression is escaped individually.
- Expressions in the attributes of GSP tags are scanned in a different lexer
state and cannot be escaped this way.
### Also in this PR
`grails-gsp-core` declared `junit-jupiter-api` but never the Jupiter engine,
so the JUnit Platform silently skipped every Jupiter-annotated test class in
the module — all of `GroovyPagesTemplateEngineTests` (23 tests) never ran.
Added the repo-standard `testRuntimeOnly
'org.junit.jupiter:junit-jupiter-engine'`; all resurrected tests pass. The
other engine-less modules with Jupiter tests (`grails-gsp/plugin`,
`grails-gsp/grails-taglib`) receive the engine transitively and were already
running them.
### Tests and docs
- `ScanTests`: escaped `${` stays in the HTML token; unescaped expressions
still tokenize; mixed escaped/unescaped side by side.
- `GroovyPagesTemplateEngineTests`: literal render, escaped next to
evaluated, JavaScript template literal end-to-end, double-backslash semantics.
- `GspCompileStaticSpec`: escaped expressions are invisible to static
compilation.
- Guide: escaping documented in the GSP Basics "Expressions" section with
the JavaScript template literal example.
Full `:grails-gsp-core:test` and `:grails-gsp:test` suites plus downstream
`:grails-taglib`, `:grails-sitemesh3`, `:grails-layout`, and `:grails-web-gsp`
all pass; `codeStyle` is clean on the touched modules.
https://claude.ai/code/session_01WtCxMe9pfmy7tiHCUr5THN
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