Adaptive price base

src/fava/application.py

@@ -230,6 +230,7 @@ def _setup_template_config(fava_app: Flask, *, incognito: bool) -> None:
     fava_app.add_template_filter(template_filters.flag_to_type)
     fava_app.add_template_filter(template_filters.format_currency)
     fava_app.add_template_filter(template_filters.meta_items)
+    fava_app.add_template_filter(template_filters.price_base)
     fava_app.add_template_filter(
         template_filters.replace_numbers
         if incognito

src/fava/template_filters.py

@@ -51,6 +51,12 @@ def format_currency(value: Decimal, currency: str | None = None) -> str:
     return g.ledger.format_decimal(value or ZERO, currency)
 
 
+def price_base(value: Decimal) -> Decimal:
+    """Return a scaled base amount for displaying a price."""
+    exponent = max(0, round(-value.log10())) if value > ZERO else 0
+    return Decimal(10) ** exponent
+
+
 FLAGS_TO_TYPES = {"*": "cleared", "!": "pending"}
 
 

src/fava/templates/_journal_table.html

@@ -1,4 +1,4 @@
-{% from 'macros/_commodity_macros.html' import render_num, render_amount %}
+{% from 'macros/_commodity_macros.html' import render_num, render_amount, render_price %}
 
 {% set short_type = {
    'balance': 'Bal',
@@ -133,7 +133,7 @@
                 <span class='num'>{{ posting.cost.number|incognito }} {{ posting.cost.currency }}
                     {{- ', {}'.format(posting.cost.date) if posting.cost.date else '' }}
                     {{- ', "{}"'.format(posting.cost.label) if posting.cost.label else '' }}</span>
-                {{ render_amount(ledger, posting.price) }}
+                {{ render_price(ledger, posting.units.currency, posting.price) }}
             </p>
             {{ _render_metadata(posting.meta|meta_items) }}
         </li>

src/fava/templates/macros/_commodity_macros.html

@@ -11,3 +11,14 @@
 {% macro render_num(ledger, currency, number) -%}
 <span title='{{ ledger.commodities.name(currency) }}'>{{ number|format_currency(currency)|incognito }} {{ currency }}</span>
 {%- endmacro %}
+
+{% macro render_price(ledger, base_currency, price) %}
+{% if price is none or price.number is none -%}
+  <span class='num'></span>
+{%- else -%}
+  {% set base = price.number|price_base %}
+  <span class='num' title='{{ ledger.commodities.name(price.currency) }}'>
+    {{- base|format_currency(base_currency)|incognito }} {{ base_currency }} = {{ (base * price.number)|format_currency(price.currency)|incognito }} {{ price.currency -}}
+  </span>
+{%- endif %}
+{% endmacro %}

tests/test_template_filters.py

@@ -6,6 +6,7 @@
 from fava.template_filters import basename
 from fava.template_filters import format_currency
 from fava.template_filters import passthrough_numbers
+from fava.template_filters import price_base
 from fava.template_filters import replace_numbers
 
 if TYPE_CHECKING:  # pragma: no cover
@@ -29,6 +30,15 @@ def test_format_currency(app: Flask) -> None:
         assert format_currency(Decimal("2.12")) == "2.12"
 
 
+def test_price_base() -> None:
+    assert price_base(Decimal(2)) == Decimal(1)
+    assert price_base(Decimal("0.5")) == Decimal(1)
+    assert price_base(Decimal("0.2")) == Decimal(10)
+    assert price_base(Decimal("0.02")) == Decimal(100)
+    assert price_base(Decimal("0.000123")) == Decimal(10000)
+    assert price_base(Decimal()) == Decimal(1)
+
+
 def test_basename() -> None:
     """Get the basename of a file path."""
     assert basename(__file__) == "test_template_filters.py"

tests/test_templates.py

@@ -27,6 +27,23 @@ def test_render_amount(app: Flask, example_ledger: FavaLedger) -> None:
         assert macro(example_ledger, create.amount("10 TEST")) == res
 
 
+def test_render_price(app: Flask, example_ledger: FavaLedger) -> None:
+    with app.test_request_context("/long-example/"):
+        app.preprocess_request()
+        macro = get_template_attribute(
+            "macros/_commodity_macros.html",
+            "render_price",
+        )
+        res = "<span class='num'></span>"
+        assert macro(example_ledger, "USD", None) == res
+        res = "  <span class='num' title='TEST'>100.00 USD = 2.00 TEST</span>"
+        assert macro(example_ledger, "USD", create.amount("0.02 TEST")) == res
+        res = (
+            "  <span class='num' title='US Dollar'>1.00 TEST = 2.00 USD</span>"
+        )
+        assert macro(example_ledger, "TEST", create.amount("2 USD")) == res
+
+
 def test_account_name(app: Flask, example_ledger: FavaLedger) -> None:
     with app.test_request_context("/long-example/"):
         app.preprocess_request()