JSON reading

Cargo.lock

@@ -1061,6 +1061,7 @@ dependencies = [
  "rustybuzz",
  "same-file",
  "serde",
+ "serde_json",
  "siphasher",
  "subsetter",
  "svg2pdf",

Cargo.toml

@@ -41,6 +41,7 @@ syntect = { version = "5", default-features = false, features = ["default-syntax
 rex = { git = "https://github.com/laurmaedje/ReX" }
 lipsum = { git = "https://github.com/reknih/lipsum" }
 csv = "1"
+serde_json = "1"
 
 # PDF export
 miniz_oxide = "0.5"

src/library/mod.rs

@@ -97,6 +97,7 @@ pub fn new() -> Scope {
     std.def_fn("symbol", utility::symbol);
     std.def_fn("lorem", utility::lorem);
     std.def_fn("csv", utility::csv);
+    std.def_fn("json", utility::json);
 
     // Predefined colors.
     std.define("black", Color::BLACK);

src/library/utility/data.rs

@@ -41,3 +41,46 @@ fn format_csv_error(error: csv::Error) -> String {
         _ => "failed to parse csv file".into(),
     }
 }
+
+/// Read structured data from a JSON file.
+pub fn json(vm: &mut Vm, args: &mut Args) -> SourceResult<Value> {
+    let Spanned { v: path, span } =
+        args.expect::<Spanned<EcoString>>("path to json file")?;
+
+    let path = vm.locate(&path).at(span)?;
+    let data = vm.world.file(&path).at(span)?;
+    let value: serde_json::Value =
+        serde_json::from_slice(&data).map_err(format_json_error).at(span)?;
+
+    Ok(convert_json(value))
+}
+
+/// Convert a JSON value to a Typst value.
+fn convert_json(value: serde_json::Value) -> Value {
+    match value {
+        serde_json::Value::Null => Value::None,
+        serde_json::Value::Bool(v) => Value::Bool(v),
+        serde_json::Value::Number(v) => match v.as_i64() {
+            Some(int) => Value::Int(int),
+            None => Value::Float(v.as_f64().unwrap_or(f64::NAN)),
+        },
+        serde_json::Value::String(v) => Value::Str(v.into()),
+        serde_json::Value::Array(v) => {
+            Value::Array(v.into_iter().map(convert_json).collect())
+        }
+        serde_json::Value::Object(v) => Value::Dict(
+            v.into_iter()
+                .map(|(key, value)| (key.into(), convert_json(value)))
+                .collect(),
+        ),
+    }
+}
+
+/// Format the user-facing JSON error message.
+fn format_json_error(error: serde_json::Error) -> String {
+    assert!(error.is_syntax() || error.is_eof());
+    format!(
+        "failed to parse json file: syntax error in line {}",
+        error.line()
+    )
+}

tests/res/bad.json

@@ -0,0 +1,4 @@
+{
+  "valid": true,
+  "invalid": True
+}

tests/res/zoo.json

@@ -0,0 +1,20 @@
+[
+  {
+    "name": "Debby",
+    "species": "Rhinoceros",
+    "weight": 1900,
+    "length": 390
+  },
+  {
+    "name": "Fluffy",
+    "species": "Tiger",
+    "weight": 115,
+    "length": 310
+  },
+  {
+    "name": "Sleepy",
+    "species": "Dolphin",
+    "weight": 150,
+    "length": 180
+  }
+]

tests/typ/utility/data.typ

@@ -1,6 +1,9 @@
-// Test reading structured CSV data.
+// Test reading structured data.
+// Ref: false
 
 ---
+// Test reading CSV data.
+// Ref: true
 #set page(width: auto)
 #let data = csv("/res/zoo.csv")
 #let cells = data(0).map(strong) + data.slice(1).flatten()
@@ -13,3 +16,14 @@
 ---
 // Error: 6-20 failed to parse csv file: found 3 instead of 2 fields in line 3
 #csv("/res/bad.csv")
+
+---
+// Test reading JSON data.
+#let data = json("/res/zoo.json")
+#test(data.len(), 3)
+#test(data(0).name, "Debby")
+#test(data(2).weight, 150)
+
+---
+// Error: 7-22 failed to parse json file: syntax error in line 3
+#json("/res/bad.json")