Add md-footnote

crates/lib/md-dev/Cargo.toml

@@ -0,0 +1,15 @@
+# Clone of
+# https://github.com/markdown-it-rust/markdown-it-plugins.rs
+
+[package]
+name = "md-dev"
+version = "0.2.0"
+publish = false
+rust-version = { workspace = true }
+edition = { workspace = true }
+
+[lints]
+workspace = true
+
+[dependencies]
+prettydiff = { workspace = true }

crates/lib/md-dev/src/lib.rs

@@ -0,0 +1,109 @@
+//! development utilities
+//!
+//! This contains shared code for reading test fixtures,
+//! testing for differences, and regenerating expected output.
+
+use prettydiff::diff_lines;
+use std::path::PathBuf;
+
+pub struct FixtureFile {
+	pub file: PathBuf,
+	pub title: String,
+	pub input: String,
+	pub expected: String,
+}
+
+/// Read a fixture file into a FixtureFile struct
+pub fn read_fixture_file(file: PathBuf) -> FixtureFile {
+	#[expect(clippy::unwrap_used)]
+	let text = std::fs::read_to_string(&file).unwrap();
+
+	let mut lines = text.lines();
+	let mut title = String::new();
+	let mut input = String::new();
+	let mut expected = String::new();
+	loop {
+		match lines.next() {
+			None => panic!("no '....' line found to signal start of input"),
+			Some(line) if line.starts_with("....") => break,
+			Some(line) => {
+				title.push_str(line);
+				title.push('\n');
+			}
+		}
+	}
+	loop {
+		match lines.next() {
+			None => panic!("no '....' line found to signal start of expected output"),
+			Some(line) if line.starts_with("....") => break,
+			Some(line) => {
+				input.push_str(line);
+				input.push('\n');
+			}
+		}
+	}
+	loop {
+		match lines.next() {
+			None => break,
+			Some(line) => {
+				expected.push_str(line);
+				expected.push('\n');
+			}
+		}
+	}
+	// strip preceding empty line in input
+	while input.starts_with('\n') {
+		input = input[1..].to_string();
+	}
+	// strip trailing empty lines from input
+	while input.ends_with('\n') {
+		input.pop();
+	}
+	// strip preceding empty line in expected
+	while expected.starts_with('\n') {
+		expected = expected[1..].to_string();
+	}
+
+	FixtureFile {
+		file,
+		title,
+		input,
+		expected,
+	}
+}
+
+/// Assert that the actual output matches the expected output,
+/// and panic with a diff if it does not.
+pub fn assert_no_diff(f: FixtureFile, actual: &str) {
+	if actual.trim_end() != f.expected.trim_end() {
+		let diff = diff_lines(&f.expected, actual);
+
+		// if environmental variable FORCE_REGEN is set, overwrite the expected output
+		if std::env::var("FORCE_REGEN").is_ok() {
+			let written = std::fs::write(
+				f.file,
+				format!(
+					"{}\n......\n\n{}\n\n......\n\n{}\n",
+					f.title.trim_end(),
+					f.input,
+					actual.trim_end()
+				),
+			)
+			.is_ok();
+			if written {
+				panic!(
+					"\n{}\nDiff:\n{}\n\nRegenerated expected output",
+					f.title, diff
+				);
+			}
+			panic!(
+				"\n{}\nDiff:\n{}\n\nFailed to regenerate expected output",
+				f.title, diff
+			)
+		}
+		panic!(
+			"\n{}\nDiff:\n{}\nSet FORCE_REGEN=true to update fixture",
+			f.title, diff
+		);
+	}
+}