Add simple logic to anki export field mappings, `if/else` #586

jzohrab · 2025-02-24T17:03:18Z

Sometimes during exports it would be useful to put one field or another in the anki note.

For example, I have two practically identical exports for German pluralization: one that puts the "parent" in the singular field, and another that puts the "term" in the singular field, because for some German words the sing and plural forms are the same.

Possible grammar options:

Like Anki: {#myfield}{ myfield }{/myfield} {^myfield}{ otherfield }{/myfield}

Like Jinja: {% if myfield %}{ myfield }{% else %}{ otherfield }{% endif %}

Like Python: { parents or term }

(No idea how difficult this is going to be, but the request makes sense).

The text was updated successfully, but these errors were encountered:

jzohrab · 2025-02-24T21:12:01Z

Some initial hacking:

from pyparsing import (
    Word, alphas, Suppress, Forward, Group, Optional, Keyword, CharsNotIn, OneOrMore, restOfLine, Regex
)

def evaluate_if_block(parsed, context):
    """Evaluate an if-else block based on a dictionary context."""
    # print(f"if block ...")
    # print(parsed)
    # print(context)
    condition = parsed[0] in context and bool(context[parsed[0]])
    # print(condition)
    ret = ""
    if condition:
        ret = parsed[1]  # Return "then" block
    elif len(parsed) > 2:  # If an "else" block exists, return it
        ret = parsed[2]

    # do substitution here ... eg. replace {term} with the actual value.
    return ret


def parse_template(template, context):
    """Parse and evaluate a template supporting `{% if %} ... {% else %} ... {% endif %}`."""
    print("-----------------------")
    print(template)

    identifier = Word(alphas + "_")  # Variable names (e.g., "term", "another")

    # **Fix:** Capture full text blocks until `{%`
    text_content = Regex(r'.*?(?={%)')

    # If-Else-Endif syntax
    if_stmt = Suppress("{% if") + identifier + Suppress("%}")
    else_stmt = Suppress("{% else %}")
    endif_stmt = Suppress("{% endif %}")

    if_expr = Group(
        if_stmt + text_content + Optional(else_stmt + text_content, default="") + endif_stmt
    )

    template_parser = OneOrMore(if_expr | identifier | text_content)

    parsed_result = template_parser.parse_string(template, parse_all=True)
    # print(parsed_result)

    # Evaluate parsed structure
    output = []
    for item in parsed_result:
        # print(f"evaluating item = {item}")
        if isinstance(item, str):
            # print("is string")
            output.append(context.get(item, item))
        else:
            # print("is array (if block)")
            output.append(evaluate_if_block(item, context))

    print(f"output = {output}")
    return output[0]

# Test Cases
template1 = "{% if term %}{term}{% else %}{parents}{% endif %}"
template2 = "{% if term %}{term}{% endif %}"  # No "else"

context1 = {"term": "world"}
context2 = {}  # "term" is missing

# test cases and what they _should_ print -- final substitutions not happening yet.
print(parse_template(template1, context1))  # "Hello, world!"
print(parse_template(template1, context2))  # "No term found."
print(parse_template(template2, context1))  # "Hello, world!"
print(parse_template(template2, context2))  # "" (empty string)

This prints out:

-----------------------
{% if term %}{term}{% else %}{parents}{% endif %}
output = ['{term}']
{term}
-----------------------
{% if term %}{term}{% else %}{parents}{% endif %}
output = ['{parents}']
{parents}
-----------------------
{% if term %}{term}{% endif %}
output = ['{term}']
{term}
-----------------------
{% if term %}{term}{% endif %}
output = ['']

This is still going to be tough to integrate into the field mapping code, b/c the various conditions would need to be evaluated, e.g. {% if tags:["val1", "val2"] %} stuff here {% endif %}, and need to check for bad outputs too.

jzohrab added this to Lute-v3 Feb 24, 2025

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Add simple logic to anki export field mappings, `if/else` #586

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Add simple logic to anki export field mappings, if/else #586

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Add simple logic to anki export field mappings, `if/else` #586

Add simple logic to anki export field mappings, `if/else` #586