* lisp/erc/erc-button.el (erc-button--nick): Add `face-cache' slot.
(erc-button-add-nickname-buttons): Pass `erc-button--nick' object, if
created', as the boolean NICK-P parameter when calling
`erc-button-add-button'.  Keeping the latter function ignorant of
`erc-button--nick' is of course preferable, but some coordination is
now required to convey and use the "face cache".  We can introduce an
abstraction, like a local variable, if this becomes an issue.
(erc-button-add-button): Use `erc--merge-prop' instead of
`erc-button-add-face' to apply button faces.  Hold off on deprecating
the latter because it provides unique functionality for nesting faces.
Also, consult NICK-P if it's an `erc-button--nick' object for the
various overriding faces it knows about.
* lisp/erc/erc-nicks.el (erc-nicks-track-faces): New option.
(erc-nicks--get-face): Make generated face `:inherit' from
`erc-nicks-backing-face'.
(erc-nicks--highlight): Just return the generated face instead of
combining it with `erc-nicks-backing-face'.
(erc-nicks--highlight-button): Set the `face-cache' slot of the
`erc-button--nick' object when `track' is loaded and initialized.
(erc-nicks-mode, erc-nicks-enable, erc-nicks-disable): Add and remove
`track' integration.
(erc-nicks--reject-uninterned-faces): New function to remove faces
created by `nicks' from buttonized speakers and mentions.  Conform
to `erc-track--face-reject-function' interface.
(erc-nicks--ourps, erc-nicks--check-normals): New function and helper
for `erc-track--alt-normals-function' interface.
(erc-nicks--setup-track-integration): New function.
(erc-nicks--remember-face-for-track): New function to cache
nick faces owned by this module.
* lisp/erc/erc.el (erc--merge-prop): Add new optional parameter
`cache-fn', and when non-nil, call it, assigning the returned value to
that of the merged property.
* test/lisp/erc/erc-nicks-tests.el (erc-nicks-list-faces): Skip
the "Inherit: " button.  (Bug#67767)

* lisp/erc/erc-track.el (erc-track--shortened-names): New variable to
stash both the latest inputs and most recent result of
`erc-track-shorten-function'.
(erc-track--shortened-names-current-hash,
erc-track--shortened-names-set, erc-track--shortened-names-get): New
pair of generalized-variable functions and helper variable for
accessing and mutating `erc-track--shorten-prefixes'.
(erc-modified-channels-display): Avoid redundant calls to
`erc-track-shorten-function'.  Mainly for use during batch processing.
* test/lisp/erc/erc-track-tests.el (erc-track--shortened-names): New
test.  (Bug#67767)

* etc/ERC-NEWS: Add entry for new behavior involving the option
`erc-track-faces-normal-list'.
* lisp/erc/erc-button.el (erc-button-nick-default-face): New face to
serve as default for `erc-button-nickname-face'.
(erc-button-nickname-face): Change default value to
`erc-button-nick-default-face'.
* lisp/erc/erc-track.el (erc-track--massage-nick-button-faces): New
function to serve as Custom :set function for priority and "normal"
face-list options.
(erc-track-faces-normal-list): Fix Custom :type by loading
`erc-button' during validation so Customize chooses the correct UI
instead of a generic form field with "(mismatch)" printed alongside
the "STATE" button.
(erc-track-faces-priority-list, erc-track-faces-normal-list): Remove
values for "buttonized" `match' module faces that, if retained, would
need updating to feature `erc-button-nick-default-face' instead of
`erc-nick-default-face'.  However, as noted in the NEWS entry, this
ordering of button face atop match face is not possible.  Use :set
function to massage saved user values.
(erc-track-ignore-normal-contenders-p): New compatibility switch to
access pre-5.6 behavior, in which faces in
`erc-track-faces-normal-list' were only considered for promotion to
the mode line if the current face occupying that pole position wasn't
present.
(erc-track-mode, erc-track-enable, erc-track-disable): Add comments
regarding perceived futility of hooking on `erc-server-001-functions'
and likely unneeded hook removal.  Run common buffer-local setup and
teardown.
(erc-track--normal-faces): New local variable, a snapshot of
`erc-track-faces-normal-list'.
(erc-track--setup): New function to stash
`erc-track-faces-normal-list' on init.
(erc-track-select-mode-line-face): Offer alternate explanation of
certain particulars in doc string.
(erc-track--alt-normals-function): New function-valued variable to
allow other modules to intervene in deciding whether to pursue and
promote a "normal" contending face.
(erc-track--select-mode-line-face): New function similar to its public
namesake except that it considers other viable candidates among the
"normal" alternatives.
(erc-track-modified-channels): Only run face selection portion when
faces are actually found.  Use `erc-track--select-mode-line-face'
instead of `erc-track-select-mode-line-face'.
* test/lisp/erc/erc-track-tests.el
(erc-track-select-mode-line-face): New test.
(erc-track-tests--select-mode-line-face): New fixture function.
(erc-track--select-mode-line-face): New test.  (Bug#67767)

* etc/ERC-NEWS: Mention change even though the API remains
undisturbed.
* lisp/erc/erc-common.el (erc-channel-user): "Encode" status prefix
slots `voice', `halfop', `op', `admin', and `owner' as single `status'
slot.  Add backward-compatible constructor.  Although the old layout
was overly sparse, since the vast majority of users have no membership
status at all, the point here is not to trade time for space but
rather to improve human readability of ERC buffer substrings
containing text props that reference `erc-channel-user' objects.
* lisp/erc/erc.el (erc--define-channel-user-status-compat-getter):
Helper macro for declaring compat-oriented "getters" for status-prefix
slots of `erc-channel-user'.
(erc-channel-user-voice, erc-channel-user-halfop, erc-channel-user-op,
erc-channel-user-admin, erc-channel-user-owner): Add compat getters.
These are not new functions.  They were previously defined by the
`erc-channel-user' `cl-defstruct' in erc-common.el.
(erc--update-cusr-status-if-changed): New helper macro to make
`erc-update-current-channel-member' more readable.
(erc-update-current-channel-member): Collapse some overly verbose
"unrolled" forms using helper macro and more compact expressions.
* test/lisp/erc/erc-tests.el (erc-channel-user): New test.

* doc/misc/erc.texi: Replace option `erc-format-nick-function' with
`erc-show-speaker-membership-status'.
* etc/ERC-NEWS: Mention shift to template-based speaker formatting.
Also mention in-buffer STATUSMSG support and various name changes and
new formatting-related options.
* lisp/erc/erc-backend.el (erc-format-privmessage): Remove forward
declaration.
(erc--determine-speaker-message-format-args): Add forward declaration.
(erc--statusmsg-target): New utility function for detecting whether
the current target is status-prefixed.
(erc-current-message-catalog): Move here from lisp/erc/erc.el.
(erc--message-speaker-catalog): New variable.
(erc--speaker-status-prefix-wanted-p): New variable specifically for
the function `erc-format-@nick' to signal it wants status-prefixes
prepended to the displayed nick.
(erc-server-PRIVMSG): Initialize `let'-bound value of
`erc--msg-prop-overrides' to a dummy `erc--tmp' property with a null
value that `erc-display-message' will "strip" before calling its
hooks.  Move away from the rather blunt symbol `msg' as a useful value
for `erc--msg'.  Instead, allow `erc-display-message' to assign the
most appropriate value based on context.  Also, bind the variable
`erc-current-message-catalog' to whatever the buffer's
`erc--message-speaker-catalog' happens to be.  Future internal modules
can set this to alternative catalogs as needed.  Additionally, detect
STATUSMSG prefixes on targets and inform the formatting logic of the
verdict.  Lastly, and most importantly, use the function
`erc--determine-speaker-message-format-args' instead of
`erc-format-privmessage' for message formatting.  Pass along the
returned "catalog key" and spec parameters to `erc-display-message'.
However, for NOTICEs, continue to render the string, as before, for
the two "echo notice" hooks.
* lisp/erc/erc-common.el (erc--ctcp-response): New "subsclass" of
`erc-response' for smuggling extra information to CTCP query handlers
in a mostly backwards-compatible way.  The same approach could be
taken with the "echo notice" hooks mentioned above.
* lisp/erc/erc-dcc.el (erc-dcc-chat-filter): Add `erc--spkr' and
`erc--speaker' properties even though these chat buffers are not
`erc-mode' buffers.
* lisp/erc/erc-fill.el (erc-fill--wrap-last-msg,
erc-fill--wrap-max-lull): Add doc strings.
(erc-fill--wrap-continued-message-p): Rework to look for `erc--spkr'-
`erc--msg' combinations as indicators of speaker continuity.
(erc-fill--wrap-rejigger-region): Remove reference to the no longer
relevant `erc-stamp-type'.  Instead, use the `erc--msg' property
combined with the `erc-timestamp' field to detect date stamps because
all are currently left-sided.
* lisp/erc/erc-stamp.el (erc-stamp--propertize-left-date-stamp): Don't
add superfluous `erc-stamp-type' property.
* lisp/erc/erc.el (erc--msg-props): Revise purpose and meaning of
`erc--msg' by removing possible value `msg', which was previously
meant to indicate that a message had a "speaker".  Instead, rely on
the separate `erc--spkr' property to convey this information, with
`erc--msg' now expressing a "type" or "role".
(erc--use-language-catalog-for-ctcp-action-p): New variable, a
compatibility switch to help transition from the `ACTION' entry of the
language catalog to the `ctcp-action' family of entries in the new
`-speaker' catalog.
(erc--ensure-spkr-prop): Update to include any passed-in environmental
overrides.
(erc--send-action-display): Restore pre-5.6 behavior when
compatibility flag enabled.  Otherwise, use new `-speaker' catalog for
formatting inserted message.
(erc--send-message-external): Overhaul to behave more faithfully in
mimicking a line submitted at the prompt of the current target buffer.
(erc--own-property-names): Remove `erc-stamp-type'.
(erc-ensure-target-buffer-on-privmsg): Add new choice variant for old
default behavior and change meaning of default to mean "except for
STATUSMSGs".  This option is newly revived for ERC 5.6.
(erc--message-speaker-statusmsg, erc--message-speaker-statusmsg-input,
erc--message-speaker-input, erc--message-speaker-input-chan-privmsg,
erc--message-speaker-input-chan-notice,
erc--message-speaker-input-query-privmsg,
erc--message-speaker-input-query-notice,
erc--message-speaker-chan-privmsg, erc--message-speaker-query-privmsg,
erc--message-speaker-chan-notice, erc--message-speaker-query-notice,
erc--message-speaker-ctcp-action,
erc--message-speaker-ctcp-action-input,
erc--message-speaker-ctcp-action-statusmsg,
erc--message-speaker-ctcp-action-statusmsg-input): New variables for
new `speaker' format-template catalog.
(erc--speakerize-nick): New helper function.
(erc--determine-speaker-message-format-args): New function to find the
appropriate format key from various contextual parameters.  Could
become the default of a function-valued variable for internal use.
(erc-show-speaker-membership-status): New option.
(erc-format-nick-function, erc-speaker-from-channel-member-function):
Declare former as an obsolete alias for the latter, and redefine
purpose slightly.
(erc-format-nick-function, erc-determine-speaker-from-user): Rename
former to latter and obsolete the old name.
(erc-format-nick, erc-determine-speaker-from-user): Rename former to
latter and obsolete old name.
(erc-format-@nick): Deprecate and adapt for use with new
template-based formatting paradigm.
(erc-format-my-nick): Move `erc-speaker' text prop toward head of
list, meaning it will end up beneath `font-lock-face' in the final
output.
(erc--format-speaker-input-message): New function to replace
`erc-format-my-nick' in-tree.
(erc-process-ctcp-query): Don't bind `erc--msg' to `msg'.  Instead,
rely on `erc-display-message' to set it to the current template key.
(erc-ctcp-query-ACTION): Prefer using formatting template, but attempt
to simulate pre-5.6 behavior when compatibility flag enabled.
(erc-display-msg): Use `erc--format-speaker-input-message' instead of
`erc-format-my-nick'.  Ignore `erc--msg-prop-overrides' with null
values.
(erc-current-message-catalog): Move to erc-backend.el.
* test/lisp/erc/erc-scenarios-base-statusmsg.el: New file.
* test/lisp/erc/erc-scenarios-stamp.el
(erc-scenarios-stamp--left/display-margin-mode): Expect format catalog
key instead of unhelpful `msg' as value of `erc--msg' prop.
* test/lisp/erc/erc-tests.el (erc-message): Render format template in
mock function and expect string in assertions.
(erc-tests--format-privmessage): New function, a helper for the
following test.
(erc-format-privmessage, erc--determine-speaker-message-format-args):
Rename former to latter and suppress deprecation warning.
(erc--determine-speaker-message-format-args/queries,
erc--determine-speaker-message-format-args/queries-as-channel): New
tests.
(erc-tests--format-my-nick): New helper function for the following
test.
(erc--format-speaker-input-message): New test.
* test/lisp/erc/resources/base/display-message/statusmsg.eld: New
file.  (Bug#67677)
; * test/lisp/erc/resources/fill/snapshots/merge-wrap-01.eld: Update.
; * test/lisp/erc/resources/fill/snapshots/merge-wrap-indicator-post-01.eld:
; Update.
; * test/lisp/erc/resources/fill/snapshots/merge-wrap-indicator-pre-01.eld:
; Update.

* etc/ERC-NEWS: Mention combined face ordering for "/me" messages.
* lisp/erc/erc-backend.el (erc-server-PRIVMSG): Bind
`erc--msg-prop-overrides' for the extent of this function's execution,
which means a large amount of code will see this variable as being
non-nil.  However, no calls to `erc-display-message' or
`erc-display-msg' should occur other than the one handling the final
insertion.  Code needing to influence the current message's "msg
props" can push new pairs onto this value, which will override any
existing collisions.
* lisp/erc/erc-fill.el (erc-fill): Switch to `erc--spkr' as sentinel
property.
(erc-fill--wrap-continued-message-p): Look for `erc--spkr' property
instead of `erc-speaker'.
* lisp/erc/erc.el (erc--msg-props): Mention `erc--spkr' in doc.
(erc--send-action-perform-ctcp): Add `erc--spkr' property.  Fix bug in
which `erc-my-nick-face' appeared below `erc-input-face' in the
speaker portion.
(erc--ensure-spkr-prop): New helper function to propagate speaker
metadata.
(erc--ranked-properties): Add `erc--spkr', `erc--ctcp', and
`erc--ephemeral'.
(erc-display-message): Use default hash table size when initializing.
Remove unnecessary assignment of `msg' to `erc--msg' for PRIVMSG and
NOTICE commands.  Bind `string' below `erc--msg-props' so that
implementers of the function form of the `erc-format-message'
templating interface can read and write the current context's "msg
props".
(erc--own-property-names): Add all `erc--msg-props' props by
subsumation.
(erc--get-speaker-bounds): Use `erc--spkr' instead of `erc--msg' as a
sentinel to detect a chat message guaranteed to have an `erc--speaker'
text-property interval.
(erc-format-privmessage, erc-format-my-nick, erc-ctcp-query-ACTION):
Add `erc--spkr' to `erc--msg-prop-overrides' when available.
* test/lisp/erc/erc-fill-tests.el: (erc-fill-tests--insert-privmsg):
Bind `erc--msg-prop-overrides'.
(erc-fill-tests--compare): Require environment variable value to match
current test name exactly when saving snapshots.  Add `erc--msg-props'
individually to white list.
* test/lisp/erc/erc-tests.el (erc--order-text-properties-from-hash):
Include `erc--spkr'.  (Bug#60936)  (Bug#67677)
; * test/lisp/erc/resources/fill/snapshots/merge-01-start.eld: Update.
; * test/lisp/erc/resources/fill/snapshots/merge-02-right.eld: Update.
; * test/lisp/erc/resources/fill/snapshots/merge-wrap-01.eld: Update.
; * test/lisp/erc/resources/fill/snapshots/merge-wrap-indicator-post-01.eld:
; Update.
; * test/lisp/erc/resources/fill/snapshots/merge-wrap-indicator-pre-01.eld:
; Update.
; * test/lisp/erc/resources/fill/snapshots/monospace-01-start.eld: Update.
; * test/lisp/erc/resources/fill/snapshots/monospace-02-right.eld: Update.
; * test/lisp/erc/resources/fill/snapshots/monospace-03-left.eld: Update.
; * test/lisp/erc/resources/fill/snapshots/monospace-04-reset.eld: Update.
; * test/lisp/erc/resources/fill/snapshots/spacing-01-mono.eld: Update.
; * test/lisp/erc/resources/fill/snapshots/stamps-left-01.eld: Update.

* lisp/erc/erc.el (erc--check-prompt-input-for-running-process):
Resolve dissonance between content of ancient `user-error' message and
condition that triggered it by favoring the former because it's
supported by the underlying mechanism, which revolves around the
`process-not-needed' symbol property.
* test/lisp/erc/erc-tests.el (erc--check-prompt-input-functions):
Revise expected output for error assertion.  (Bug#66073, originally
from bug#54536, and included for discussion in bug#67677)

* lisp/erc/erc-backend.el (erc-server-396, erc-server-396-functions):
Define response handler for 396 numeric.  For now, always display the
message in the active buffer rather than bother with something like
`erc-once-with-server-event' to try and suss out when this is a
response to something client-initiated, like a /VHOST.  Do this
despite most users probably wanting the message to appear in the
server buffer alone when the response is server-initiated.  The
`labeled-response' extension will hopefully make dealing with such
matters less of a crapshoot.
* lisp/erc/erc.el (erc--parse-user-regexp-pedantic): Tweak slightly to
allow null groups and favor host.
(erc--parse-user-regexp-legacy, erc--parse-user-regexp): Remove the
first variable but preserve its value as that of the second.
(erc--parse-nuh): New function.  The behavior is nuanced and complex
and so not easily described in a doc string.
(erc-message-english-396): Define format template for 396 response.
* test/lisp/erc/erc-scenarios-misc-commands.el
(erc-scenarios-misc-commands--VHOST): New test.
* test/lisp/erc/erc-tests.el (erc-parse-user): Move "pedantic" section
to new test.
(erc--parse-nuh): New test.
* test/lisp/erc/resources/commands/vhost.eld: New test data file.
(Bug#67677)

* etc/ERC-NEWS: Fix entry regarding `erc-input-refoldp'.
* lisp/erc/erc-common.el (erc-input): Remove `refoldp' slot, which was
to be new in 5.6, in order to reduce churn in the extremely unlikely
event that third-party code uses the read-syntax of these objects or
ones subclassed from it for some other purpose, outside of
`erc-pre-send-functions'.
(erc--input-split) Add `refoldp' slot here instead.
* lisp/erc/erc.el (erc-pre-send-functions): Amend doc string to stress
that `refoldp' is not a real slot.
(erc--input-ensure-hook-context, erc-input-refoldp): New function, an
impostor accessor for the nonexistent `refoldp' slot of `erc-input',
and a helper function for asserting a valid context at runtime.
(erc--run-send-hooks): Don't copy over `refoldp' from the
`erc--input-lines' object to the working `erc-insert' object.  Check
the insertion context's `erc--input-split' object instead of the
hook's `erc-insert' object when deciding whether to resplit.
* test/lisp/erc/erc-tests.el: Adjust test environment to satisfy
assertion.  (Bug#62947)