Disable Rails field_with_errors wrapper engine-wide via field_error_proc #339

Context

PR #337 added prefix/suffix support to text_field, wrapping inputs in usa-input-group with adjacent prefix/suffix divs. The implementation includes a scoped workaround: when a prefixed/suffixed input is in an error state, Rails' default field_with_errors wrapper is stripped via regex. Without the strip, the wrapper sits between .usa-input-prefix and <input> and breaks the .usa-input-prefix + input CSS adjacency selector that supplies the input's padding-left.

The fix addresses the immediate bug but only for prefix/suffix. Rails injects a <div class="field_with_errors"> wrapper that Strata never wants, and the same bug will reproduce with any future USWDS feature that uses adjacent-sibling selectors (character counters, date pickers, combo boxes).

Proposal

Set Rails' field_error_proc to a pass-through at the engine level, then remove the scoped strip from text_field.

ActionView::Base.field_error_proc = ->(html_tag, _instance) { html_tag }

Why this is safe

Strata already renders its own error markup for every form helper:

• usa-input--error on the input element
• usa-form-group--error on the surrounding form group
• usa-error-message span with the validation message

Rails' field_with_errors wrapper adds nothing on top of that. It's redundant for any consumer of Strata's form builders.

Why this matters now

USWDS uses adjacent-sibling and child selectors in several components:

• .usa-input-prefix + input (this PR)
• .usa-input-suffix + .usa-character-count__message (character counters)
• .usa-date-picker__wrapper > input (date pickers)

Each will hit the same wrapper-breaks-adjacency bug as it gets added. Fixing the wrapper at the engine level preempts the whole class.

Precedent

navapbc/archive-md-famli did this in config/application.rb:112.

Scope of the follow-up PR

• Add the field_error_proc override in Strata's engine boot config
• Remove the scoped strip from Strata::FormBuilder#text_field
• Keep the "blank prefix/suffix as absent" spec (independent of field_error_proc)
• Adjust or drop the "keeps the input as the immediate sibling of the prefix in error states" spec; the adjacency will hold by default once the wrapper is gone, making that spec a tautology

Open question

Whether to fold an ADR into the follow-up PR. Blast radius (changes rendered HTML for every Strata consumer in error states) and rationale (Strata's error markup makes Rails' redundant) both suggest yes.