Add source and test files.

source/lib.rs

@@ -0,0 +1,71 @@
+/*!
+# toml-frontmatter
+
+> **TOML frontmatter parser.**
+
+See the [`parse`] documentation for an example.
+
+## License
+
+Distributed under the [Apache License 2.0](https://spdx.org/licenses/Apache-2.0.html) and [MIT](https://spdx.org/licenses/MIT.html) licenses, see [LICENSE-Apache](https://git.bauke.xyz/Holllo/toml-frontmatter/src/branch/main/LICENSE-Apache) and [LICENSE-MIT](https://git.bauke.xyz/Holllo/toml-frontmatter/src/branch/main/LICENSE-MIT) for more information.
+*/
+
+#![forbid(unsafe_code)]
+#![warn(missing_docs, clippy::missing_docs_in_private_items)]
+
+use {
+  anyhow::{anyhow, Result},
+  serde::Deserialize,
+};
+
+/**
+Parse a struct that implements [`serde::Deserialize`] from frontmatter and
+return the remaining contents of the string.
+
+## Errors
+
+This function will return an [`Err`] when:
+
+- the data doesn't have a frontmatter section,
+- the frontmatter isnt' at the beginning of the data.
+
+## Example
+
+```rust
+#[derive(serde::Deserialize)]
+struct Frontmatter {
+  date: String,
+}
+
+let sample = r#"
+---toml
+date = "2023-01-01"
+---
+
+Some **Markdown**. Or something else!
+"#.trim();
+
+let (frontmatter, markdown) = toml_frontmatter::parse::<Frontmatter>(sample).unwrap();
+```
+*/
+pub fn parse<'a, D: Deserialize<'a>>(data: &'a str) -> Result<(D, &'a str)> {
+  let start_marker = "---toml\n";
+  let end_marker = "\n---\n";
+
+  let (start, end) = match (data.find(start_marker), data.find(end_marker)) {
+    (Some(start), Some(end)) => (start, end),
+    _ => return Err(anyhow!("Missing frontmatter")),
+  };
+
+  if start != 0 {
+    return Err(anyhow!("Frontmatter not at beginning of data"));
+  }
+
+  let start = start + start_marker.len();
+  let frontmatter = &data[start..end];
+
+  let end = end + end_marker.len();
+  let extra = &data[end..];
+
+  Ok((toml::from_str::<D>(frontmatter)?, extra.trim_start()))
+}

tests/errors.rs

@@ -0,0 +1,20 @@
+#[test]
+#[should_panic(expected = "Missing frontmatter")]
+fn test_missing_frontmatter() {
+  toml_frontmatter::parse::<()>("# Heading").unwrap();
+}
+
+#[test]
+#[should_panic(expected = "Frontmatter not at beginning of data")]
+fn test_frontmatter_not_at_start() {
+  let sample = r#"
+# Heading
+
+---toml
+date = "2023-01-01"
+---
+
+Text."#;
+
+  toml_frontmatter::parse::<()>(sample).unwrap();
+}

tests/parsing.rs

@@ -0,0 +1,29 @@
+use {
+  anyhow::Result,
+  insta::{assert_snapshot, assert_toml_snapshot},
+  serde::{Deserialize, Serialize},
+};
+
+#[derive(Debug, Deserialize, Serialize)]
+struct Frontmatter {
+  date: String,
+}
+
+#[test]
+fn test_parsing() -> Result<()> {
+  let sample = r#"
+---toml
+date = "2023-01-01"
+---
+
+# Some Markdown
+
+With text!"#;
+
+  let (toml, markdown) = toml_frontmatter::parse::<Frontmatter>(sample.trim())?;
+
+  assert_toml_snapshot!("toml", toml);
+  assert_snapshot!("markdown", markdown);
+
+  Ok(())
+}

tests/snapshots/parsing__markdown.snap

@@ -0,0 +1,7 @@
+---
+source: tests/parsing.rs
+expression: markdown
+---
+# Some Markdown
+
+With text!

tests/snapshots/parsing__toml.snap

@@ -0,0 +1,5 @@
+---
+source: tests/parsing.rs
+expression: toml
+---
+date = '2023-01-01'