Improve log validation error formatting with CLI styling

NEWS.md

@@ -1,5 +1,7 @@
 # vitals (development version)
 
+* Internal `expect_valid_log()` now styles Pydantic output for readability 
+  (#159 by howardbaik).
 
 * `$eval()` and `$log()` will now write log files to the same default 
   directory--the one specified when initializing the Task object. 

tests/testthat/helper-valid_log.R

@@ -67,14 +67,45 @@ expect_valid_log <- local({
       stdout = TRUE,
       stderr = TRUE
     )
+
     status <- attr(result, "status")
 
+    # "inst/test/inspect/logs/2025-03-24T10-39-36-05-00_simple-arithmetic_fQ9mYnqZFhtEuUenPpJgKL.json"
+    if (length(result) == 1) {
+      formatted_message <- cli::format_message(c(
+        "The generated log did not pass the pydantic model:",
+        glue::glue("{{.field {result[1]}}}")
+      ))
+      expect(
+        is.null(status) || status == 0,
+        formatted_message
+      )
+    }
+
+    # Make the result more readable by removing redundant elements
+    # and formatting indices with cli (#159)
+    result <- result[!grepl("For further information visit", result)]
+    result_length <- length(result)
+    field_positions <- seq(2, result_length, by = 2)
+
+    for (pos in field_positions) {
+      result[pos] <- glue::glue("{{.field {result[pos]}}}")
+    }
+
+    result_with_breaks <- result[1]
+    for (i in seq(2, length(result), by = 2)) {
+      result_with_breaks <- c(result_with_breaks, "", result[i:(i + 1)])
+    }
+
+    formatted_message <- cli::format_message(c(
+      "The generated log did not pass the pydantic model:",
+      "",
+      result_with_breaks
+    ))
+
     expect(
       is.null(status) || status == 0,
-      paste0(
-        c("The generated log did not pass the pydantic model: ", result),
-        collapse = "\n"
-      )
+      formatted_message
     )
   }
 })