Add num_format filter (#1460)

* Add `num_format` filter for displaying formatted numbers

* Register the filter

* Update docs

* Make `locale` argument required

* Revert "Make `locale` argument required"

This reverts commit 9cdbf28591.

* Pull the default locale from the site config

* Add note about defaults to the docs

* Add missing borrow

Cargo.lock

@@ -57,6 +57,15 @@ version = "0.1.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "70033777eb8b5124a81a1889416543dddef2de240019b674c81285a2635a7e1e"
 
+[[package]]
+name = "arrayvec"
+version = "0.4.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cd9fd44efafa8690358b7408d253adf110036b88f55672a933f01d616ad9b1b9"
+dependencies = [
+ "nodrop",
+]
+
 [[package]]
 name = "arrayvec"
 version = "0.5.2"
@@ -1163,7 +1172,7 @@ version = "0.7.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6607c62aa161d23d17a9072cc5da0be67cdfc89d3afb1e8d9c842bebc2525ffe"
 dependencies = [
- "arrayvec",
+ "arrayvec 0.5.2",
  "bitflags",
  "cfg-if 1.0.0",
  "ryu",
@@ -1533,6 +1542,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "nodrop"
+version = "0.1.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "72ef4a56884ca558e5ddb05a1d1e7e1bfd9a68d9ed024c21704cc98872dae1bb"
+
 [[package]]
 name = "nom"
 version = "5.1.2"
@@ -1627,6 +1642,16 @@ dependencies = [
  "winapi 0.3.9",
 ]
 
+[[package]]
+name = "num-format"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bafe4179722c2894288ee77a9f044f02811c86af699344c498b0840c698a2465"
+dependencies = [
+ "arrayvec 0.4.12",
+ "itoa",
+]
+
 [[package]]
 name = "num-integer"
 version = "0.1.44"
@@ -2571,6 +2596,7 @@ dependencies = [
  "library",
  "mockito",
  "nom-bibtex",
+ "num-format",
  "rendering",
  "reqwest",
  "serde",

components/site/src/tpls.rs

@@ -12,6 +12,10 @@ pub fn register_early_global_fns(site: &mut Site) -> TeraResult<()> {
             site.permalinks.clone(),
         )?,
     );
+    site.tera.register_filter(
+        "num_format",
+        filters::NumFormatFilter::new(&site.config.default_language),
+    );
 
     site.tera.register_function(
         "get_url",

components/templates/Cargo.toml

@@ -16,6 +16,7 @@ serde_derive = "1"
 sha2 = "0.9"
 url = "2"
 nom-bibtex = "0.3"
+num-format = "0.4"
 
 errors = { path = "../errors" }
 utils = { path = "../utils" }

components/templates/src/filters.rs

@@ -6,7 +6,10 @@ use std::path::PathBuf;
 use base64::{decode, encode};
 use config::Config;
 use rendering::{render_content, RenderContext};
-use tera::{to_value, try_get_value, Filter as TeraFilter, Result as TeraResult, Tera, Value};
+use tera::{
+    to_value, try_get_value, Error as TeraError, Filter as TeraFilter, Result as TeraResult, Tera,
+    Value,
+};
 
 use crate::load_tera;
 
@@ -72,13 +75,43 @@ pub fn base64_decode<S: BuildHasher>(
     Ok(to_value(&String::from_utf8(decode(s.as_bytes()).unwrap()).unwrap()).unwrap())
 }
 
+#[derive(Debug)]
+pub struct NumFormatFilter {
+    default_language: String,
+}
+
+impl NumFormatFilter {
+    pub fn new<S: Into<String>>(default_language: S) -> Self {
+        Self { default_language: default_language.into() }
+    }
+}
+
+impl TeraFilter for NumFormatFilter {
+    fn filter(&self, value: &Value, args: &HashMap<String, Value>) -> TeraResult<Value> {
+        use num_format::{Locale, ToFormattedString};
+
+        let num = try_get_value!("num_format", "value", i64, value);
+        let locale = match args.get("locale") {
+            Some(locale) => try_get_value!("num_format", "locale", String, locale),
+            None => self.default_language.clone(),
+        };
+        let locale = Locale::from_name(&locale).map_err(|_| {
+            TeraError::msg(format!(
+                "Filter `num_format` was called with an invalid `locale` argument: `{}`.",
+                locale
+            ))
+        })?;
+        Ok(to_value(num.to_formatted_string(&locale)).unwrap())
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use std::{collections::HashMap, path::PathBuf};
 
     use tera::{to_value, Filter};
 
-    use super::{base64_decode, base64_encode, MarkdownFilter};
+    use super::{base64_decode, base64_encode, MarkdownFilter, NumFormatFilter};
     use config::Config;
 
     #[test]
@@ -201,4 +234,44 @@ mod tests {
             assert_eq!(result.unwrap(), to_value(expected).unwrap());
         }
     }
+
+    #[test]
+    fn num_format_filter() {
+        let tests = vec![
+            (100, "100"),
+            (1_000, "1,000"),
+            (10_000, "10,000"),
+            (100_000, "100,000"),
+            (1_000_000, "1,000,000"),
+        ];
+
+        for (input, expected) in tests {
+            let args = HashMap::new();
+            let result = NumFormatFilter::new("en").filter(&to_value(input).unwrap(), &args);
+            let result = dbg!(result);
+            assert!(result.is_ok());
+            assert_eq!(result.unwrap(), to_value(expected).unwrap());
+        }
+    }
+
+    #[test]
+    fn num_format_filter_with_locale() {
+        let tests = vec![
+            ("en", 1_000_000, "1,000,000"),
+            ("en-IN", 1_000_000, "10,00,000"),
+            // Note:
+            // U+202F is the "NARROW NO-BREAK SPACE" code point.
+            // When displayed to the screen, it looks like a space.
+            ("fr", 1_000_000, "1\u{202f}000\u{202f}000"),
+        ];
+
+        for (locale, input, expected) in tests {
+            let mut args = HashMap::new();
+            args.insert("locale".to_string(), to_value(locale).unwrap());
+            let result = NumFormatFilter::new("en").filter(&to_value(input).unwrap(), &args);
+            let result = dbg!(result);
+            assert!(result.is_ok());
+            assert_eq!(result.unwrap(), to_value(expected).unwrap());
+        }
+    }
 }

docs/content/documentation/templates/overview.md

@@ -81,6 +81,22 @@ Encode the variable to base64.
 ### base64_decode
 Decode the variable from base64.
 
+### num_format
+Format a number into its string representation.
+
+```jinja2
+{{ 1000000 | num_format }}
+<!-- 1,000,000 -->
+```
+
+By default this will format the number using the locale set by `config.default_language` in config.toml.
+
+To format a number for a specific locale, you can use the `locale` argument and pass the name of the desired locale:
+
+```jinja2
+{{ 1000000 | num_format(locale="en-IN") }}
+<!-- 10,00,000 -->
+```
 
 ## Built-in functions