This helper improves the message given when an expectation
fails in a source-mapping test.

PR Close #39717

…39717)

When the `preserveWhitespaces` is not true, the template parser will
process the parsed AST nodes to remove excess whitespace. Since the
generated `goog.getMsg()` statements rely upon the AST nodes after
this whitespace is removed, the i18n extraction must make a second pass.

Previously this resulted in innacurrate source-spans for the i18n text and
placeholder nodes that were extracted in the second pass.

This commit fixes this by reusing the source-spans from the first pass
when extracting the nodes in the second pass.

Fixes #39671

PR Close #39717

When parsing for i18n messages, interpolated strings are
split into `Text` and `Placeholder` pieces.  The method that
does this `_visitTextWithInterpolation()` was becoming too
complex. This commit refactors that method along with some
associated functions that it uses.

PR Close #39717

…39717)

When the `preserveWhitespaces` is not true, the template parser will
process the parsed AST nodes to remove excess whitespace. Since the
generated `goog.getMsg()` statements rely upon the AST nodes after
this whitespace is removed, the i18n extraction must make a second pass.

Previously this resulted in innacurrate source-spans for the i18n text and
placeholder nodes that were extracted in the second pass.

This commit fixes this by reusing the source-spans from the first pass
when extracting the nodes in the second pass.

Fixes #39671

PR Close #39717

When parsing for i18n messages, interpolated strings are
split into `Text` and `Placeholder` pieces.  The method that
does this `_visitTextWithInterpolation()` was becoming too
complex. This commit refactors that method along with some
associated functions that it uses.

PR Close #39717