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Suraj Yadav
d3469056cb
The control flow migration determines whether an `*ngIf` uses a `then`
and/or `else` clause by regex matching the raw microsyntax string for
the literal keywords `then`/`else`. The regexes only checked that the
keyword was preceded by a non-word character, but not that it was
followed by one.
As a result, a template reference name that merely starts with `then`
(e.g. `else thenBlock`) or `else` was misidentified as the `then`/`else`
keyword itself. This caused the migration to take the wrong code path
(e.g. then+else instead of else-only), which in turn made
`getTemplateName()` compute a `slice(start, end)` with `start > end`,
producing an empty template name. That empty placeholder was never
resolved and was silently emitted as an invalid
`<ng-template [ngTemplateOutlet]=""></ng-template>`, dropping the
original template content without any warning.
Add a negative lookahead `(?![\w\d])` to both regexes so `then`/`else`
are only matched as whole keywords, not as a prefix of a longer
template reference name.
Fixes #69914
(cherry picked from commit 5ad8231397)