[lvgl] Allow text substitution for NaN (#11712)

esphome/components/lvgl/helpers.py

@@ -3,6 +3,8 @@ import re
 from esphome import config_validation as cv
 from esphome.const import CONF_ARGS, CONF_FORMAT
 
+CONF_IF_NAN = "if_nan"
+
 lv_uses = {
     "USER_DATA",
     "LOG",
@@ -21,23 +23,48 @@ lv_fonts_used = set()
 esphome_fonts_used = set()
 lvgl_components_required = set()
 
-
-def validate_printf(value):
-    cfmt = r"""
+# noqa
+f_regex = re.compile(
+    r"""
     (                                  # start of capture group 1
     %                                  # literal "%"
-    (?:[-+0 #]{0,5})                   # optional flags
+    [-+0 #]{0,5}                   # optional flags
+    (?:\d+|\*)?                        # width
+    (?:\.(?:\d+|\*))?                  # precision
+    (?:h|l|ll|w|I|I32|I64)?            # size
+    f                                  # type
+    )
+    """,
+    flags=re.VERBOSE,
+)
+# noqa
+c_regex = re.compile(
+    r"""
+    (                                  # start of capture group 1
+    %                                  # literal "%"
+    [-+0 #]{0,5}                   # optional flags
     (?:\d+|\*)?                        # width
     (?:\.(?:\d+|\*))?                  # precision
     (?:h|l|ll|w|I|I32|I64)?            # size
     [cCdiouxXeEfgGaAnpsSZ]             # type
     )
-    """  # noqa
-    matches = re.findall(cfmt, value[CONF_FORMAT], flags=re.VERBOSE)
+    """,
+    flags=re.VERBOSE,
+)
+
+
+def validate_printf(value):
+    format_string = value[CONF_FORMAT]
+    matches = c_regex.findall(format_string)
     if len(matches) != len(value[CONF_ARGS]):
         raise cv.Invalid(
             f"Found {len(matches)} printf-patterns ({', '.join(matches)}), but {len(value[CONF_ARGS])} args were given!"
         )
+
+    if value.get(CONF_IF_NAN) and len(f_regex.findall(format_string)) != 1:
+        raise cv.Invalid(
+            "Use of 'if_nan' requires a single valid printf-pattern of type %f"
+        )
     return value
 
 

esphome/components/lvgl/lv_validation.py

@@ -33,7 +33,13 @@ from .defines import (
     call_lambda,
     literal,
 )
-from .helpers import add_lv_use, esphome_fonts_used, lv_fonts_used, requires_component
+from .helpers import (
+    CONF_IF_NAN,
+    add_lv_use,
+    esphome_fonts_used,
+    lv_fonts_used,
+    requires_component,
+)
 from .types import lv_font_t, lv_gradient_t
 
 opacity_consts = LvConstant("LV_OPA_", "TRANSP", "COVER")
@@ -412,7 +418,13 @@ class TextValidator(LValidator):
                 str_args = [str(x) for x in value[CONF_ARGS]]
                 arg_expr = cg.RawExpression(",".join(str_args))
                 format_str = cpp_string_escape(format_str)
-                return literal(f"str_sprintf({format_str}, {arg_expr}).c_str()")
+                sprintf_str = f"str_sprintf({format_str}, {arg_expr}).c_str()"
+                if nanval := value.get(CONF_IF_NAN):
+                    nanval = cpp_string_escape(nanval)
+                    return literal(
+                        f"(std::isfinite({arg_expr}) ? {sprintf_str} : {nanval})"
+                    )
+                return literal(sprintf_str)
             if time_format := value.get(CONF_TIME_FORMAT):
                 source = value[CONF_TIME]
                 if isinstance(source, Lambda):

esphome/components/lvgl/schemas.py

@@ -20,7 +20,7 @@ from esphome.core.config import StartupTrigger
 
 from . import defines as df, lv_validation as lvalid
 from .defines import CONF_TIME_FORMAT, LV_GRAD_DIR
-from .helpers import requires_component, validate_printf
+from .helpers import CONF_IF_NAN, requires_component, validate_printf
 from .layout import (
     FLEX_OBJ_SCHEMA,
     GRID_CELL_SCHEMA,
@@ -54,6 +54,7 @@ PRINTF_TEXT_SCHEMA = cv.All(
         {
             cv.Required(CONF_FORMAT): cv.string,
             cv.Optional(CONF_ARGS, default=list): cv.ensure_list(cv.lambda_),
+            cv.Optional(CONF_IF_NAN): cv.string,
         },
     ),
     validate_printf,

tests/components/lvgl/lvgl-package.yaml

@@ -726,6 +726,12 @@ lvgl:
                 - logger.log:
                     format: "Spinbox value is %f"
                     args: [x]
+                - lvgl.label.update:
+                    id: hello_label
+                    text:
+                      format: "value is %.1f now"
+                      args: [x]
+                      if_nan: "Value unknown"
         - button:
             styles: spin_button
             id: spin_down