* lisp/erc/erc-common.el (erc--input-split): Suppress warning for
obsolete variable `erc-send-this' in init form.
* lisp/erc/erc-goodies.el (erc--keep-place-indicator-setup): Use macro
`erc--restore-initialize-priors' to preserve last session's indicator
position, if any.
(erc-keep-place-indicator-mode, erc-keep-place-indicator-enable): Use
convenience function to show missing-dependency notice.
* lisp/erc/erc-sasl.el (erc-sasl-auth-source-password-as-host): Merge
redundant `when' forms for clarity.
(erc-sasl--init): Remove unused function.
(erc-sasl-mode, erc-sasl-enable): Use helper to restore
`erc-sasl--options', essentially inlining the body of the now defunct
`erc-sasl--init'.
* lisp/erc/erc.el (erc--restore-initialize-priors): New macro to help
local modules and mode hooks prefer existing state over initializing
anew.
(erc--warn-once-before-connect): Add helper function to display
an "error notice" just after module setup.
(erc-accidental-paste-threshold-seconds) Improve doc string.
* test/lisp/erc/erc-goodies-tests.el
(erc-controls-highlight--examples, erc-controls-highlight--inverse,
erc-controls-highlight--motd, erc-keep-place-indicator-mode): Remove
feature check.  For the latter, also start fake process and shadow
`erc-connect-pre-hook'.
* test/lisp/erc/erc-tests.el (erc--restore-initialize-priors): New
test.  Also see test/lisp/erc/erc-scenarios-base-local-modules.el for
a more realistic exercising of this functionality.  (Bug#60936)

* etc/ERC-NEWS: Mention revised role of `erc-pre-send-functions'
relative to line splitting.
* lisp/erc/erc-common.el (erc-input): Add new slot `refoldp' to allow
`erc-pre-send-functions' members to indicate that splitting should
occur a second time after all members have had their say.
(erc--input-split): Specify some defaults for overridden slots and
explicitly declare some types for good measure.
* lisp/erc/erc-goodies.el (erc-noncommands-mode,
erc-noncommands-enable, erc-noncommands-disable): Replace
`erc-pre-send-functions' with `erc--input-review-functions'.
* lisp/erc/erc-ring.el (erc-ring-enable, erc-ring-disable,
erc-ring-mode): Subscribe to `erc--input-review-functions' instead of
`erc-pre-send-functions' for `erc--add-to-input-ring'.
* lisp/erc/erc.el (erc-pre-send-functions): Note some nuances
regarding line splitting in doc string and note that a new slot is
available.
(erc--pre-send-split-functions, erc--input-review-functions): Rename
former to latter, while also obsoleting.  Remove large comment.  Add
new default member `erc--run-input-validation-checks'.
(erc-send-modify-hook): Replace the obsolete `erc-send-pre-hook' and
`erc-send-this' with `erc-pre-send-functions' in doc string.
(erc--check-prompt-input-for-excess-lines): Don't trim trailing
blanks.  Rework to also report overages in characters as well as
lines.
(erc--run-input-validation-hooks): New function to adapt an
`erc--input-split' object to `erc--check-prompt-input-functions'.
(erc-send-current-line): Run `erc--input-review-functions' in place of
the validation hooks they've subsumed.  Call `erc--send-input-lines'
instead of the now retired but not deprecated `erc-send-input'.
(erc--run-send-hooks, erc--send-input-lines): New functions that
together form an alternate version of `erc-send-input'.  They operate
on input linewise but make accommodations for older interfaces.
* test/lisp/erc/erc-tests.el (erc-ring-previous-command): Replace
`erc-pre-send-functions' with `erc--input-review-functions'.
(erc-tests--with-process-input-spy): Shadow
`erc--input-review-functions'.
(erc-check-prompt-input-for-excess-lines): Don't expect trailing
blanks to be trimmed.
(erc--run-send-hooks): New test.  (Bug#62947)

* lisp/erc/erc-common.el (erc--neuter-custom-variable-state): Remove
function.  ERC famously toggles global minor-mode vars during normal
operations, which adds noise to its customization buffers because
`customize-variable-state' always sees an activated module's mode
variable as having "CHANGED".  To suppress this annoyance, a
workaround was employed that used a dishonest `:get' function to
simply return the "saved value," when present.  While this improved
the Customize experience, it also misled users, which likely wasn't
justified.
(erc--make-show-me-widget): Add helper to avoid forward declarations.
(erc--prepare-custom-module-type): Don't deprive users of a working
minor-mode toggle.
(erc--find-feature): New function to guess the feature of a module's
containing library.
(define-erc-module): Remove `:get' keyword.  Specify `:require'
instead, whose value may be nil.  Users who currently have mode vars
in their `custom-file' won't be impacted by this addition because
those `custom-set-variables' entries will still lack a REQUEST list
and hence won't incur a startup penalty.  And new users intent on
using the toggle will hopefully do so with the knowledge they're
opting in to requiring ERC on startup, which is not the case if they
follow the recommended practice of using `erc-modules' instead.
(erc-with-server-buffer): Inline `erc-server-buffer'.
* test/lisp/erc/erc-tests.el (erc-process-input-line): Use helper.
(define-erc-module--global): Change expected expansion.  (Bug#60935)

* lisp/erc/erc-common.el: (erc-with-server-buffer): Modify slightly to
use `buffer-local-value' when possible.
* test/lisp/erc/erc-services-tests.el
(erc-services-tests--auth-source-plstore-standard-entries,
erc-services-tests--auth-source-plstore-standard-secrets): Remove
unused variables.
(erc-services-tests--auth-source-plstore-standard-announced): Add new
var to hold common plstore document.
(erc--auth-source-search--plstore-standard,
erc--auth-source-search--plstore-announced,
erc--auth-source-search--plstore-overrides): Use string literals for
text-document content.
(erc-services-tests--auth-source-json-standard-entries): Remove unused
variable.
(erc-services-tests--auth-source-json-standard-announced): Add new
variable.
(erc--auth-source-search--json-standard,
erc--auth-source-search--json-announced,
erc--auth-source-search--json-overrides): Use string literals for
text-document content.
(erc-services-tests--secrets-search-items): Add new helper function.
(erc--auth-source-search--secrets-standard,
erc--auth-source-search--secrets-announced,
erc--auth-source-search--secrets-overrides): Use helper to mock
`secrets-search-items' instead of misleading lambda.
* lisp/erc/erc-tests.el (erc-with-server-buffer): Add test.

* lisp/erc/erc-common.el (erc--fill-module-docstring): Add helper to
fill doc strings.
(erc--assemble-toggle, define-erc-module): Use helper to fill doc
string.
* test/lisp/erc/erc-tests.el (define-minor-mode--global,
define-minor-mode--local): Adjust expected output for generated doc
strings.  (Bug#60935.)

* lisp/erc/erc-common.el: (erc--inside-mode-toggle-p): Add global var
to inhibit mode toggles from being run by `erc-update-modules'.  It
must be non-nil inside custom-set functions for mode toggles created
by `define-erc-module'.
(erc--favor-changed-reverted-modules-state): Add new helper to show a
"SET" Custom state for `erc-modules' except when reverting to the
default value because \"STANDARD\" always takes precedence, as
explained somewhat in bug#12864.
(erc--assemble-toggle): Don't modify `erc-modules' when run from
custom-set function.
(erc--neuter-custom-variable-state): Add new function to serve as a
phony getter that deceives Customize into thinking the variable is
always set to its standard value.  The justification for this is that
toggling a module's minor mode in Customize has never worked and has
only sewn confusion in new users.  Without this hack, mode widgets
show a state of "CHANGED outside Customize", which alone is probably
preferable, except that they all end up toggled open, bringing them
unwanted attention and distracting the user.
(erc--tick-module-checkbox): Add helper to toggle the appropriate
checkbox in the `erc-modules' widget when a user interactively toggles
a minor-mode state variable.
(erc--prepare-custom-module-type): Create spec for minor-mode Custom
`:type', deferring various aspects until module-definition time.
(define-erc-module): Add `:get' and `:type' keywords to be passed to
`defcustom' definition for global modules.
* lisp/erc/erc.el (erc-modules): Inhibit `erc-update-modules' when run
from a minor-mode toggle's custom-set function.
* test/lisp/erc/erc-tests.el (define-erc-module--global,
define-erc-module--local): Update `erc-modules' mutations with
`erc--inside-mode-toggle-p' guard conditions.  (Bug#60935.)

* lisp/erc/erc-capab.el: Add property crutch to help ERC find module's
Custom group.
* lisp/erc/erc-common.el (erc--find-group): Add new function, a helper
for finding an existing ERC module's Custom group based on
`define-erc-module' params.  Prefer `group-documentation' as a
sentinel over symbol properties owned by Customize because they might
not be present if the group isn't yet associated with any custom
variables.
(define-erc-module): Set `:group' keyword value more accurately,
falling back to `erc' when no associated group has been defined.
* test/lisp/erc/erc-tests.el (erc--find-group, erc--find-group--real):
New tests.
(define-erc-module--global, define-erc-module--local): Expect the
`:group' keyword to be the unevaluated `erc--find-group'
form.  (Bug#60935.)

* lisp/erc/erc-common.el (erc--features-to-modules,
erc--modules-to-features, erc--module-name-migrations): Remove unused
internal functions.
(erc--normalize-module-symbol): Make aware of new migration scheme
based on symbol properties.
* lisp/erc/erc-page.el: Add autoload cookie for module migration.
* lisp/erc/erc-pcomplete.el: Add autoload cookies for module
migration.
* lisp/erc/erc-services.el: Add autoload cookie for module migration.
* lisp/erc/erc-sound.el: Add autoload cookie for module migration.
* lisp/erc/erc-stamp.el: Add autoload cookie for module migration.
* lisp/erc/erc.el (erc-modules): Reorder default value, sorted by
`string<' so that Customize does not consider the value to have been
edited.  Remove non-existent module `hecomplete' from lineup and swap
a couple more to maintain sorted order.  Change `:initialize' function
to tag all symbols for built-in modules with an `erc--module'
property.  In the `:set' function, ensure third-party modules appear
after the sorted and normalized built-ins, but in user-defined order.
Do this to prevent all modules, built-ins included, from ending up as
populated form fields for the "other" checkbox in the Customize
interface.
(erc--find-mode): Add helper function for `erc--update-modules'.
(erc--update-modules): Always resolve module names and only
conditionally attempt to require corresponding features.
* test/lisp/erc/erc-tests.el (erc-tests--modules): Add manifest for
asserting built-in modules and features.  This is easier to verify
visually than looking at the custom-type set for `erc-modules'.
(erc-modules--initialize): New test.
(erc-modules--internal-property): Add test.
(erc--normalize-module-symbol): New test.
(erc--find-mode): New test.
(erc--update-modules) Adapt to new paradigm and make more
comprehensive.  (Bug#60954.)

* lisp/erc/erc-backend.el (erc--hide-prompt): Change hook depth from 0
to 91 to allow the `move-to-prompt' module to do its thing.  This
feature was added by bug#54826 and first appeared in Emacs 29.
* lisp/erc/erc-common.el (erc-server-user): Remove erroneous comment.
The `buffers' field is a list of buffers.
* test/lisp/erc/erc-tests.el (erc-hide-prompt): Use `erc--target'
instead of `erc-default-recipients' because this is new code.

* lisp/erc/erc-common.el (define-erc-module): Add symbol property
`erc-module' to minor modes defined as part of a module.
* lisp/erc/erc.el (erc--merge-local-modes): Be more conservative when
persisting local minor-mode state across ERC sessions.  User and
third-party modes that were not defined via `define-erc-modules'
should be left alone.
(erc-open): Run major-mode hooks and enable minor modes after prompt
has been set up.  This ensures that module-setup code can access a
fully initialized `erc-input-marker'.
* test/lisp/erc/erc-tests.el (erc--merge-local-modes): Add mocks for
`erc-module' symbol property and a test case covering some foreign ERC
mode.
(define-erc-module--global, define-erc-module--local): Expect the
`erc-module' symbol property to be defined for mode symbols and
aliases.  (Bug#60784.)