add context to card rendering, and rework related hooks

- the context exists for the lifecycle of one card's render,
and caches calls to things like .card() to avoid add-ons needing to
do their own cache management.
- add-ons can optionally add extra data to the context if they need
it across multiple filters
- removed card_will_render. the legacy hook is still available for
now
- card_did_render is now called only once, with both front and back
text

pylib/anki/collection.py

@@ -31,7 +31,7 @@ from anki.rsbackend import RustBackend
 from anki.sched import Scheduler as V1Scheduler
 from anki.schedv2 import Scheduler as V2Scheduler
 from anki.tags import TagManager
-from anki.template import render_card
+from anki.template import TemplateRenderContext, render_card
 from anki.types import NoteType, QAData, Template
 from anki.utils import (
     devMode,
@@ -635,7 +635,6 @@ where c.nid = n.id and c.id in %s group by nid"""
     def _renderQA(
         self, data: QAData, qfmt: Optional[str] = None, afmt: Optional[str] = None
     ) -> Dict[str, Union[str, int]]:
-        "Returns hash of id, question, answer."
         # extract info from data
         split_fields = splitFields(data[6])
         card_ord = data[4]
@@ -665,35 +664,39 @@ where c.nid = n.id and c.id in %s group by nid"""
         fields["CardFlag"] = self._flagNameFromCardFlags(flag)
         fields["c%d" % (card_ord + 1)] = "1"
 
-        # legacy
+        # legacy hook
         fields = runFilter("mungeFields", fields, model, data, self)
 
-        # allow add-ons to modify the available fields & templates
+        ctx = TemplateRenderContext(self, data, fields)
-        (qfmt, afmt) = hooks.card_will_render((qfmt, afmt), fields, model, data)
 
-        # render fields
+        # render fields. if any custom filters are encountered,
+        # the field_filter hook will be called.
         try:
-            qatext = render_card(self, qfmt, afmt, fields, card_ord)
+            qtext, atext = render_card(self, qfmt, afmt, ctx)
         except anki.rsbackend.BackendException as e:
             errmsg = _("Card template has a problem:") + f"<br>{e}"
-            qatext = (errmsg, errmsg)
+            qtext = errmsg
+            atext = errmsg
 
-        ret: Dict[str, Any] = dict(q=qatext[0], a=qatext[1], id=card_id)
+        # avoid showing the user a confusing blank card if they've
+        # forgotten to add a cloze deletion
+        if model["type"] == MODEL_CLOZE:
+            if not self.models._availClozeOrds(model, data[6], False):
+                qtext = (
+                    qtext
+                    + "<p>"
+                    + _("Please edit this note and add some cloze deletions. (%s)")
+                    % ("<a href=%s#cloze>%s</a>" % (HELP_SITE, _("help")))
+                )
 
         # allow add-ons to modify the generated result
-        for type in "q", "a":
+        (qtext, atext) = hooks.card_did_render((qtext, atext), ctx)
-            ret[type] = hooks.card_did_render(
-                ret[type], type, fields, model, data, self
-            )
 
-            # empty cloze?
+        # legacy hook
-            if type == "q" and model["type"] == MODEL_CLOZE:
+        qtext = runFilter("mungeQA", qtext, "q", fields, model, data, self)
-                if not self.models._availClozeOrds(model, data[6], False):
+        atext = runFilter("mungeQA", atext, "a", fields, model, data, self)
-                    ret["q"] += "<p>" + _(
-                        "Please edit this note and add some cloze deletions. (%s)"
-                    ) % ("<a href=%s#cloze>%s</a>" % (HELP_SITE, _("help")))
 
-        return ret
+        return dict(q=qtext, a=atext, id=card_id)
 
     def _qaData(self, where="") -> Any:
         "Return [cid, nid, mid, did, ord, tags, flds, cardFlags] db query"

pylib/anki/hooks.py

@@ -18,7 +18,7 @@ import decorator
 
 import anki
 from anki.cards import Card
-from anki.types import QAData
+from anki.template import TemplateRenderContext
 
 # New hook/filter handling
 ##############################################################################
@@ -58,71 +58,31 @@ class _CardDidRenderFilter:
     """Can modify the resulting text after rendering completes."""
 
     _hooks: List[
-        Callable[
+        Callable[[Tuple[str, str], TemplateRenderContext], Tuple[str, str]]
-            [
-                str,
-                str,
-                Dict[str, str],
-                Dict[str, Any],
-                QAData,
-                "anki.storage._Collection",
-            ],
-            str,
-        ]
     ] = []
 
     def append(
-        self,
+        self, cb: Callable[[Tuple[str, str], TemplateRenderContext], Tuple[str, str]]
-        cb: Callable[
-            [
-                str,
-                str,
-                Dict[str, str],
-                Dict[str, Any],
-                QAData,
-                "anki.storage._Collection",
-            ],
-            str,
-        ],
     ) -> None:
-        """(text: str, side: str, fields: Dict[str, str], notetype: Dict[str, Any], data: QAData, col: anki.storage._Collection)"""
+        """(text: Tuple[str, str], ctx: TemplateRenderContext)"""
         self._hooks.append(cb)
 
     def remove(
-        self,
+        self, cb: Callable[[Tuple[str, str], TemplateRenderContext], Tuple[str, str]]
-        cb: Callable[
-            [
-                str,
-                str,
-                Dict[str, str],
-                Dict[str, Any],
-                QAData,
-                "anki.storage._Collection",
-            ],
-            str,
-        ],
     ) -> None:
         if cb in self._hooks:
             self._hooks.remove(cb)
 
     def __call__(
-        self,
+        self, text: Tuple[str, str], ctx: TemplateRenderContext
-        text: str,
+    ) -> Tuple[str, str]:
-        side: str,
-        fields: Dict[str, str],
-        notetype: Dict[str, Any],
-        data: QAData,
-        col: anki.storage._Collection,
-    ) -> str:
         for filter in self._hooks:
             try:
-                text = filter(text, side, fields, notetype, data, col)
+                text = filter(text, ctx)
             except:
                 # if the hook fails, remove it
                 self._hooks.remove(filter)
                 raise
-        # legacy support
-        runFilter("mungeQA", text, side, fields, notetype, data, col)
         return text
 
 
@@ -153,53 +113,6 @@ class _CardOdueWasInvalidHook:
 card_odue_was_invalid = _CardOdueWasInvalidHook()
 
 
-class _CardWillRenderFilter:
-    """Can modify the available fields and question/answer templates prior to rendering."""
-
-    _hooks: List[
-        Callable[
-            [Tuple[str, str], Dict[str, str], Dict[str, Any], QAData], Tuple[str, str]
-        ]
-    ] = []
-
-    def append(
-        self,
-        cb: Callable[
-            [Tuple[str, str], Dict[str, str], Dict[str, Any], QAData], Tuple[str, str]
-        ],
-    ) -> None:
-        """(templates: Tuple[str, str], fields: Dict[str, str], notetype: Dict[str, Any], data: QAData)"""
-        self._hooks.append(cb)
-
-    def remove(
-        self,
-        cb: Callable[
-            [Tuple[str, str], Dict[str, str], Dict[str, Any], QAData], Tuple[str, str]
-        ],
-    ) -> None:
-        if cb in self._hooks:
-            self._hooks.remove(cb)
-
-    def __call__(
-        self,
-        templates: Tuple[str, str],
-        fields: Dict[str, str],
-        notetype: Dict[str, Any],
-        data: QAData,
-    ) -> Tuple[str, str]:
-        for filter in self._hooks:
-            try:
-                templates = filter(templates, fields, notetype, data)
-            except:
-                # if the hook fails, remove it
-                self._hooks.remove(filter)
-                raise
-        return templates
-
-
-card_will_render = _CardWillRenderFilter()
-
-
 class _DeckAddedHook:
     _hooks: List[Callable[[Dict[str, Any]], None]] = []
 
@@ -253,22 +166,31 @@ exporters_list_created = _ExportersListCreatedHook()
 
 
 class _FieldFilterFilter:
-    _hooks: List[Callable[[str, str, str, Dict[str, str]], str]] = []
+    """Allows you to define custom {{filters:..}}
         
-    def append(self, cb: Callable[[str, str, str, Dict[str, str]], str]) -> None:
+        Your add-on can check filter_name to decide whether it should modify
-        """(field_text: str, field_name: str, filter_name: str, fields: Dict[str, str])"""
+        field_text or not before returning it."""
+
+    _hooks: List[Callable[[str, str, str, TemplateRenderContext], str]] = []
+
+    def append(self, cb: Callable[[str, str, str, TemplateRenderContext], str]) -> None:
+        """(field_text: str, field_name: str, filter_name: str, ctx: TemplateRenderContext)"""
         self._hooks.append(cb)
 
-    def remove(self, cb: Callable[[str, str, str, Dict[str, str]], str]) -> None:
+    def remove(self, cb: Callable[[str, str, str, TemplateRenderContext], str]) -> None:
         if cb in self._hooks:
             self._hooks.remove(cb)
 
     def __call__(
-        self, field_text: str, field_name: str, filter_name: str, fields: Dict[str, str]
+        self,
+        field_text: str,
+        field_name: str,
+        filter_name: str,
+        ctx: TemplateRenderContext,
     ) -> str:
         for filter in self._hooks:
             try:
-                field_text = filter(field_text, field_name, filter_name, fields)
+                field_text = filter(field_text, field_name, filter_name, ctx)
             except:
                 # if the hook fails, remove it
                 self._hooks.remove(filter)

pylib/anki/latex.py

@@ -7,12 +7,13 @@ import html
 import os
 import re
 import shutil
-from typing import Any, Dict, Optional
+from typing import Any, Optional, Tuple
 
 import anki
 from anki import hooks
 from anki.lang import _
-from anki.types import NoteType, QAData
+from anki.template import TemplateRenderContext
+from anki.types import NoteType
 from anki.utils import call, checksum, isMac, namedtmp, stripHTML, tmpdir
 
 pngCommands = [
@@ -47,15 +48,18 @@ def stripLatex(text) -> Any:
     return text
 
 
-# media code and some add-ons depend on the current name
+def on_card_did_render(
-def mungeQA(
+    text: Tuple[str, str], ctx: TemplateRenderContext
-    html: str,
+) -> Tuple[str, str]:
-    type: str,
+    qtext, atext = text
-    fields: Dict[str, str],
+
-    model: NoteType,
+    qtext = render_latex(qtext, ctx.note_type(), ctx.col())
-    data: QAData,
+    atext = render_latex(atext, ctx.note_type(), ctx.col())
-    col: anki.storage._Collection,
+
-) -> str:
+    return (qtext, atext)
+
+
+def render_latex(html: str, model: NoteType, col: anki.storage._Collection,) -> str:
     "Convert TEXT with embedded latex tags to image links."
     for match in regexps["standard"].finditer(html):
         html = html.replace(match.group(), _imgLink(col, match.group(1), model))
@@ -184,4 +188,4 @@ def _errMsg(type: str, texpath: str) -> Any:
 
 
 # setup q/a filter - type ignored due to import cycle
-hooks.card_did_render.append(mungeQA)  # type: ignore
+hooks.card_did_render.append(on_card_did_render)  # type: ignore

pylib/anki/media.py

@@ -17,7 +17,7 @@ from typing import Any, Callable, List, Optional, Tuple, Union
 from anki.consts import *
 from anki.db import DB, DBError
 from anki.lang import _
-from anki.latex import mungeQA
+from anki.latex import render_latex
 from anki.template import expand_clozes
 from anki.utils import checksum, isMac, isWin
 
@@ -222,7 +222,7 @@ create table meta (dirMod int, lastUsn int); insert into meta values (0, 0);
             strings = [string]
         for string in strings:
             # handle latex
-            string = mungeQA(string, None, None, model, None, self.col)
+            string = render_latex(string, model, self.col)
             # extract filenames
             for reg in self.regexps:
                 for match in re.finditer(reg, string):

pylib/anki/template.py

@@ -15,7 +15,7 @@ the filter is skipped.
 Add-ons can register a filter with the following code:
 
 from anki import hooks
-hooks.field_replacement.append(myfunc)
+hooks.field_filter.append(myfunc)
 
 This will call myfunc, passing the field text in as the first argument.
 Your function should decide if it wants to modify the text by checking
@@ -29,35 +29,98 @@ template_legacy.py file, using the legacy addHook() system.
 from __future__ import annotations
 
 import re
-from typing import Dict, List, Optional, Tuple
+from typing import Any, Dict, List, Optional, Tuple
 
 import anki
 from anki import hooks
-from anki.hooks import runFilter
 from anki.rsbackend import TemplateReplacementList
 from anki.sound import stripSounds
+from anki.types import NoteType, QAData
+
+
+class TemplateRenderContext:
+    """Holds information for the duration of one card render.
+
+    This may fetch information lazily in the future, so please avoid
+    using the _private fields directly."""
+
+    def __init__(
+        self, col: anki.storage._Collection, qadata: QAData, fields: Dict[str, str]
+    ) -> None:
+        self._col = col
+        self._qadata = qadata
+        self._fields = fields
+
+        self._note_type: Optional[NoteType] = None
+        self._card: Optional[anki.cards.Card] = None
+        self._note: Optional[anki.notes.Note] = None
+
+        # if you need to store extra state to share amongst rendering
+        # hooks, you can insert it into this dictionary
+        self.extra_state: Dict[str, Any] = {}
+
+    def col(self) -> anki.storage._Collection:
+        return self._col
+
+    def fields(self) -> Dict[str, str]:
+        return self._fields
+
+    def card_id(self) -> int:
+        return self._qadata[0]
+
+    def note_id(self) -> int:
+        return self._qadata[1]
+
+    def deck_id(self) -> int:
+        return self._qadata[3]
+
+    def card_ord(self) -> int:
+        return self._qadata[4]
+
+    def card(self) -> Optional[anki.cards.Card]:
+        """Returns the card being rendered. Will return None in the add screen.
+
+        Be careful not to call .q() or .a() on the card, or you'll create an
+        infinite loop."""
+        if not self._card:
+            try:
+                self._card = self.col().getCard(self.card_id())
+            except:
+                return None
+
+        return self._card
+
+    def note(self) -> anki.notes.Note:
+        if not self._note:
+            self._note = self.col().getNote(self.note_id())
+
+        return self._note
+
+    def note_type(self) -> NoteType:
+        if not self._note_type:
+            self._note_type = self.col().models.get(self._qadata[2])
+
+        return self._note_type
 
 
 def render_card(
-    col: anki.storage._Collection,
+    col: anki.storage._Collection, qfmt: str, afmt: str, ctx: TemplateRenderContext
-    qfmt: str,
-    afmt: str,
-    fields: Dict[str, str],
-    card_ord: int,
 ) -> Tuple[str, str]:
     """Renders the provided templates, returning rendered q & a text.
 
     Will raise if the template is invalid."""
-    (qnodes, anodes) = col.backend.render_card(qfmt, afmt, fields, card_ord)
+    (qnodes, anodes) = col.backend.render_card(qfmt, afmt, ctx.fields(), ctx.card_ord())
 
-    qtext = apply_custom_filters(qnodes, fields, front_side=None)
+    qtext = apply_custom_filters(qnodes, ctx, front_side=None)
-    atext = apply_custom_filters(anodes, fields, front_side=qtext)
+    atext = apply_custom_filters(anodes, ctx, front_side=qtext)
 
     return qtext, atext
 
 
 def apply_custom_filters(
-    rendered: TemplateReplacementList, fields: Dict[str, str], front_side: Optional[str]
+    rendered: TemplateReplacementList,
+    ctx: TemplateRenderContext,
+    front_side: Optional[str],
 ) -> str:
     "Complete rendering by applying any pending custom filters."
     # template already fully rendered?
@@ -76,11 +139,16 @@ def apply_custom_filters(
             field_text = node.current_text
             for filter_name in node.filters:
                 field_text = hooks.field_filter(
-                    field_text, node.field_name, filter_name, fields
+                    field_text, node.field_name, filter_name, ctx
                 )
-                # legacy hook - the second and fifth argument are no longer used
+                # legacy hook - the second and fifth argument are no longer used.
-                field_text = runFilter(
+                field_text = anki.hooks.runFilter(
-                    "fmod_" + filter_name, field_text, "", fields, node.field_name, ""
+                    "fmod_" + filter_name,
+                    field_text,
+                    "",
+                    ctx.fields(),
+                    node.field_name,
+                    "",
                 )
 
             res += field_text

pylib/tools/genhooks.py

@@ -55,42 +55,25 @@ hooks = [
     Hook(
         name="tag_added", args=["tag: str"], legacy_hook="newTag", legacy_no_args=True,
     ),
-    Hook(
-        name="card_will_render",
-        args=[
-            "templates: Tuple[str, str]",
-            "fields: Dict[str, str]",
-            "notetype: Dict[str, Any]",
-            "data: QAData",
-        ],
-        return_type="Tuple[str, str]",
-        doc="Can modify the available fields and question/answer templates prior to rendering.",
-    ),
-    Hook(
-        name="card_did_render",
-        args=[
-            "text: str",
-            "side: str",
-            "fields: Dict[str, str]",
-            "notetype: Dict[str, Any]",
-            "data: QAData",
-            # the hook in latex.py needs access to the collection and
-            # can't rely on the GUI's mw.col
-            "col: anki.storage._Collection",
-        ],
-        return_type="str",
-        legacy_hook="mungeQA",
-        doc="Can modify the resulting text after rendering completes.",
-    ),
     Hook(
         name="field_filter",
         args=[
             "field_text: str",
             "field_name: str",
             "filter_name: str",
-            "fields: Dict[str, str]",
+            "ctx: TemplateRenderContext",
         ],
         return_type="str",
+        doc="""Allows you to define custom {{filters:..}}
+        
+        Your add-on can check filter_name to decide whether it should modify
+        field_text or not before returning it.""",
+    ),
+    Hook(
+        name="card_did_render",
+        args=["text: Tuple[str, str]", "ctx: TemplateRenderContext",],
+        return_type="Tuple[str, str]",
+        doc="Can modify the resulting text after rendering completes.",
     ),
 ]