date-picker-data

Author: robertbastian

tutorials/date-picker-data.md

@@ -41,7 +41,7 @@ This will generate a `ccp.blob` file containing data for Chakma.
 To use blob data, we will need to add the `icu_provider_blob` crate to our project:
 
 ```console
-cargo add icu_provider_blob
+cargo add icu_provider_blob --features alloc
 ```
 
 We also need to enable the `serde` feature on the `icu` crate to enable deserialization support:
@@ -58,29 +58,23 @@ locale is Chakma:
 use icu::locale::locale;
 use icu_provider_blob::BlobDataProvider;
 
-// Just below the imports (fill in the path):
-const CCP_BLOB_PATH: &str = "<absolute path to ccp.blob>";
-
-let datetime_formatter = if locale == locale!("ccp") {
+// replace the date_formatter creation
+let date_formatter = if locale == locale!("ccp") {
     println!("Using buffer provider");
 
-    let blob = std::fs::read(CCP_BLOB_PATH)
+    let blob = std::fs::read("ccp.blob")
         .expect("blob should read successfully")
         .into();
 
     let provider =
         BlobDataProvider::try_new_from_blob(blob).expect("deserialization should succeed");
 
-    DateTimeFormatter::try_new_with_buffer_provider(
-        &provider,
-        &(&locale).into(),
-        Default::default(),
-    )
-    .expect("should have data for selected locale")
+    DateTimeFormatter::try_new_with_buffer_provider(&provider, locale.into(), YMD::medium())
+        .expect("should have data for selected locale")
 } else {
     // As before
-    DateTimeFormatter::try_new(&(&locale).into(), Default::default())
-        .expect("should have data for selected locale")
+    DateTimeFormatter::try_new(locale.into(), YMD::medium())
+        .expect("should have data for specified locale")
 };
 ```
 
@@ -106,22 +100,19 @@ function load_blob(url, callback) {
 
 if (localeStr == "ccp") {
     load_blob("https://storage.googleapis.com/static-493776/icu4x_2023-11-03/ccp.blob", (blob) => {
-        let dateTimeFormatter = ICU4XDateTimeFormatter.create_with_lengths(
-            ICU4XDataProvider.create_from_byte_slice(blob),
+        let dateTimeFormatter = DateTimeFormatter.createYmdtWithProvider(
+            DataProvider.createFromBlob(blob),
             locale,
-            ICU4XDateLength.Medium,
-            ICU4XTimeLength.Medium,
+            DateTimeLength.Long,
         );
-        document.getElementById("output").innerText = dateFormatter.format_iso_datetime(isoDateTime);
+        document.getElementById("output").innerText = dateTimeFormatter.formatIso(isoDate, time);
     })
 } else {
-    let dateTimeFormatter = ICU4XDateTimeFormatter.create_with_lengths(
-        ICU4XDataProvider.create_compiled(),
-        locale,
-        ICU4XDateLength.Medium,
-        ICU4XTimeLength.Medium,
+    let dateTimeFormatter = DateTimeFormatter.createYmdt(
+            locale,
+            DateTimeLength.Long,
     );
-    document.getElementById("output").innerText = dateFormatter.format_iso_datetime(isoDateTime);
+    document.getElementById("output").innerText = dateTimeFormatter.formatIso(isoDate, time);
 }
 ```
 
@@ -134,43 +125,36 @@ Note: the following steps are currently only possible in Rust. 🤷
 When we ran `icu4x-datagen`, we passed `--markers all`, which make it generate *all* data for the Chakma locale, even though we only need date formatting. We can make `icu4x-datagen` analyze our binary to figure out which markers are needed:
 
 ```console
-icu4x-datagen --markers-for-bin target/debug/tutorial --locales ccp --format blob --out ccp_smaller.blob
+cargo build --release
+icu4x-datagen --markers-for-bin target/release/tutorial --locales ccp --format blob --out ccp_smaller.blob
 ```
 
-Note: you usually want to build with the `--release` flag, and analyze that binary, but we don't have all day.
+Note: you usually want to build with the `--release` flag, and analyze that binary.
 
 This should generate a lot fewer markers!
 
 Let's look at the sizes:
 
 ```console
 wc -c *.blob
-# 656767 ccp.blob
-#  45471 ccp_smaller.blob
+# 5448603 ccp.blob
+#   13711 ccp_smaller.blob
 ```
 
 This is much better! Rerun your app with `ccp_smaller.blob` to make sure it still works!
 
 ## 5. Slimming the data pack ... again
 
-The last datagen invocation still produced a lot of markers, as you saw in its output. This is because we used the `DateFormatter` API, which can format dates for a lot of different calendars. However, if we are only using it with an Gregorian calendar date, so we don't need Coptic, Indian, etc. date formatting data.
+The last datagen invocation still produced a lot of markers, as you saw in its output. This is because we used the `DateTimeFormatter` API, which can format dates for a lot of different calendars (remember `en-u-ca-hebrew`). However, if we were only using it with a Gregorian calendar date, we wouldn't need Coptic, Indian, etc. date formatting data. Now, how do we communicate this to `--markers-for-bin`? Turns out, `icu::datetime` also exposes a `FixedCalendarDateTimeFormatter`, which is generic in a single calendar type. If you use this API instead, `--markers-for-bin` will only include the markers for that one calendar type.
 
-We've seen that `DateFormatter` pulls in a lot of data. It would be nice if we could tell it that we'll only ever use it with Gregorian dates. Turns out we can! `icu::datetime` also exposes a `TypedDateFormatter<C>`, which is generic in a single calendar type. If you use this API instead (instantiated as `TypedDateFormatter<Gregorian>`), `--markers-for-bin` will give you exactly the markers we manually selected in the last section. However, now you can be sure that you didn't make a mistake selecting the markers (which would be an awkward runtime error), and that you will never accidentally pass a non-Gregorian date into the formatter (which would an awkward runtime error with `DateFormatter`, but is a compile-time error with `TypeDateFormatter`).
+Replace the `DateTimeFormatter::try_new` calls with `FixedCalendarDateTimeFormatter::try_new`, and change the `format` invocation to convert the input to the Gregorian calendar:
 
 ```rust
-let date_formatter = TypedDateFormatter::<Gregorian>::try_new_with_length(
-    &(&locale).into(),
-    length::Date::Medium,
-)
-.expect("should have data for selected locale");
-
-println!(
-    "Date: {}",
-    // We need to convert to the explicit calendar via `.to_calendar()`. 
-    date_formatter.format(&iso_date.to_calendar(Gregorian)),
-);
+    println!("Date: {}", date_formatter.format(&iso_date.to_calendar(Gregorian)));
 ```
 
+The generic type of `FixedCalendarDateTimeFormatter` will be inferred from the input, which now has type `&Date<Gregorian>` now. Unlike `DateTimeFormatter`, `FixedCalendarDateTimeFormatter` never applies calendar conversions on its input, so it will be a `FixedCalendarDateTimeFormatter<Gregorian, ...>`.
+
 Now we can run datagen with `--markers-for-bin` again:
 
 ```console
@@ -181,20 +165,22 @@ icu4x-datagen --markers-for-bin target/release/tutorial --locales ccp --format b
 The output will be much shorter:
 
 ```console
-INFO  [icu_provider_export::export_impl] Generating marker datetime/gregory/datelengths@1
-INFO  [icu_provider_export::export_impl] Generating marker datetime/gregory/datesymbols@1
-INFO  [icu_provider_export::export_impl] Generating marker datetime/week_data@1
-INFO  [icu_provider_export::export_impl] Generating marker decimal/symbols@2
-INFO  [icu_provider_export::export_impl] Generating marker plurals/ordinal@1
+2025-05-14T14:26:52.306Z INFO  [icu_provider_export::export_impl] Generated marker DatetimeNamesMonthGregorianV1
+2025-05-14T14:26:52.308Z INFO  [icu_provider_export::export_impl] Generated marker DatetimeNamesYearGregorianV1
+2025-05-14T14:26:52.312Z INFO  [icu_provider_export::export_impl] Generated marker DatetimePatternsDateGregorianV1
+2025-05-14T14:26:52.324Z INFO  [icu_provider_export::export_impl] Generated marker DecimalDigitsV1
+2025-05-14T14:26:52.325Z INFO  [icu_provider_export::export_impl] Generated marker DecimalSymbolsV1
 ```
 
 And the blob will also be much smaller at the sizes:
 
 ```console
 wc -c *.blob
-# 656767 ccp.blob
-#  45471 ccp_smaller.blob
-#   4639 ccp_smallest.blob
+# 5448603 ccp.blob
+#   13711 ccp_smaller.blob
+#    4711 ccp_smallest.blob
 ```
 
 Rerun your app with `ccp_smallest.blob` to make sure it still works!
+
+Does the locale `en-u-ca-hebrew` still use the Hebrew calendar? Why is that?