From bc535f7b7169d9e0ef26faca108518f4005cc76c Mon Sep 17 00:00:00 2001
From: Martin Haug <mhaug@live.de>
Date: Thu, 29 Dec 2022 11:49:01 +0100
Subject: [PATCH] `read` function

---
 library/src/compute/data.rs |  39 +++++++++++++++++++++++++++++++++++-
 library/src/lib.rs          |   1 +
 tests/res/hello.txt         |   1 +
 tests/res/invalid-utf8.txt  | Bin 0 -> 70 bytes
 tests/typ/compute/data.typ  |  15 +++++++++++++-
 5 files changed, 54 insertions(+), 2 deletions(-)
 create mode 100644 tests/res/hello.txt
 create mode 100644 tests/res/invalid-utf8.txt

diff --git a/library/src/compute/data.rs b/library/src/compute/data.rs
index a018c09a6..a519e8e6e 100644
--- a/library/src/compute/data.rs
+++ b/library/src/compute/data.rs
@@ -4,6 +4,40 @@ use typst::diag::{format_xml_like_error, FileError};
 
 use crate::prelude::*;
 
+/// # Read file
+/// Read plain text from a file.
+///
+/// The file will be read and returned as a string.
+///
+/// ## Example
+/// ```
+/// #let text = read("data.html")
+///
+/// An HTML file could look like this:
+/// #raw(text, lang: "html")
+/// ```
+///
+/// ## Parameters
+/// - path: EcoString (positional, required)
+///   Path to a file.
+///
+/// - returns: EcoString
+///
+/// ## Category
+/// data-loading
+#[func]
+pub fn read(vm: &Vm, args: &mut Args) -> SourceResult<Value> {
+    let Spanned { v: path, span } = args.expect::<Spanned<EcoString>>("path to file")?;
+
+    let path = vm.locate(&path).at(span)?;
+    let data = vm.world().file(&path).at(span)?;
+
+    let text = String::from_utf8(data.to_vec())
+        .map_err(|_| "file is not valid utf-8")
+        .at(span)?;
+    Ok(Value::Str(text.into()))
+}
+
 /// # CSV
 /// Read structured data from a CSV file.
 ///
@@ -184,7 +218,10 @@ fn convert_json(value: serde_json::Value) -> Value {
 /// 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())
+    format!(
+        "failed to parse json file: syntax error in line {}",
+        error.line()
+    )
 }
 
 /// # XML
diff --git a/library/src/lib.rs b/library/src/lib.rs
index a4c6fc30e..e345bbeef 100644
--- a/library/src/lib.rs
+++ b/library/src/lib.rs
@@ -124,6 +124,7 @@ fn scope() -> Scope {
     std.def_func::<compute::EvenFunc>("even");
     std.def_func::<compute::OddFunc>("odd");
     std.def_func::<compute::ModFunc>("mod");
+    std.def_func::<compute::ReadFunc>("read");
     std.def_func::<compute::CsvFunc>("csv");
     std.def_func::<compute::JsonFunc>("json");
     std.def_func::<compute::XmlFunc>("xml");
diff --git a/tests/res/hello.txt b/tests/res/hello.txt
new file mode 100644
index 000000000..5dd01c177
--- /dev/null
+++ b/tests/res/hello.txt
@@ -0,0 +1 @@
+Hello, world!
\ No newline at end of file
diff --git a/tests/res/invalid-utf8.txt b/tests/res/invalid-utf8.txt
new file mode 100644
index 0000000000000000000000000000000000000000..71308112150558cf42a7b12ef117f1a9c1eb7684
GIT binary patch
literal 70
TcmezOpF!#WUj_wAFoO~RJoqF6

literal 0
HcmV?d00001

diff --git a/tests/typ/compute/data.typ b/tests/typ/compute/data.typ
index c1def7d55..5a0f76c6b 100644
--- a/tests/typ/compute/data.typ
+++ b/tests/typ/compute/data.typ
@@ -1,6 +1,19 @@
-// Test reading structured data.
+// Test reading structured data and files.
 // Ref: false
 
+---
+// Test reading plain text files
+#let data = read("../../res/hello.txt")
+#test(data, "Hello, world!")
+
+---
+// Error: 18-41 file not found (searched at res/missing.txt)
+#let data = read("../../res/missing.txt")
+
+---
+// Error: 18-46 file is not valid utf-8
+#let data = read("../../res/invalid-utf8.txt")
+
 ---
 // Test reading CSV data.
 // Ref: true