Implement changelog update functionality. (#646)

2 notes:
* This PR correctly writes back to Cargo.toml file however the original
format is not preserved. Any easy way to do that?
* Not yet handling updates to crates that depend on originated change.
That is next.

crates/cli-tools/src/changelog.rs

@@ -24,7 +24,7 @@ use std::io::BufRead;
 
 use anyhow::{anyhow, bail, ensure, Context, Result};
 use clap::ValueEnum;
-use semver::Version;
+use semver::{Prerelease, Version};
 use tokio::process::Command;
 
 use crate::cargo::metadata;
@@ -58,6 +58,38 @@ impl Changelog {
         Self::parse(&String::from_utf8(fs::read(path).await?)?)
     }
 
+    async fn write_file(&self, path: &str) -> Result<()> {
+        fs::write(path, self.to_string().as_bytes()).await
+    }
+
+    fn push_description(&mut self, severity: Severity, content: &str) -> Result<()> {
+        let content = if content.starts_with("- ") { content } else { &format!("- {content}") };
+        let current_release = self.get_or_create_release_mut();
+        current_release.push_content(severity, content)
+    }
+
+    // Gets newest (first) release. Creates a new one if newest release is not prerelease.
+    fn get_or_create_release_mut(&mut self) -> &mut Release {
+        let current_release = self.releases.first().unwrap();
+
+        // Current version is released, insert a new one.
+        if current_release.version.pre.is_empty() {
+            let mut next_version = Version::new(
+                current_release.version.major,
+                current_release.version.minor,
+                current_release.version.patch + 1,
+            );
+
+            next_version.pre = Prerelease::new("git").unwrap();
+
+            let new_release = Release::from(next_version);
+
+            self.releases.insert(0, new_release);
+        }
+
+        self.releases.first_mut().unwrap()
+    }
+
     /// Parses and validates a changelog.
     fn parse(input: &str) -> Result<Changelog> {
         let mut releases: Vec<Release> = Vec::new();
@@ -147,6 +179,24 @@ impl Changelog {
         );
         Ok(())
     }
+
+    async fn sync_cargo_toml(&self, path: &str) -> Result<()> {
+        let expected_version = &self.releases.first().unwrap().version;
+
+        let mut sed = Command::new("sed");
+        sed.arg("-i");
+        sed.arg(format!("s#^version = .*#version = \"{expected_version}\"#"));
+        sed.arg("Cargo.toml");
+        cmd::execute(sed.current_dir(path)).await?;
+
+        Ok(())
+    }
+
+    async fn sync_dependencies(&self, _path: &str) -> Result<()> {
+        // TODO
+
+        Ok(())
+    }
 }
 
 impl Display for Changelog {
@@ -209,6 +259,19 @@ struct Release {
     contents: BTreeMap<Severity, Vec<String>>,
 }
 
+impl Release {
+    fn push_content(&mut self, severity: Severity, content: &str) -> Result<()> {
+        self.contents.entry(severity).or_default().push(content.to_string());
+        Ok(())
+    }
+}
+
+impl From<Version> for Release {
+    fn from(version: Version) -> Self {
+        Release { version, contents: BTreeMap::new() }
+    }
+}
+
 impl Display for Release {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         writeln!(f, "## {}\n", self.version)?;
@@ -260,12 +323,17 @@ pub async fn execute_ci() -> Result<()> {
 }
 
 /// Updates a changelog file and changelog files of dependencies.
-pub async fn execute_change(path: &str, _severity: &Severity, _description: &str) -> Result<()> {
-    ensure!(fs::exists(path).await, "Crate does not exist: {path}");
+pub async fn execute_change(path: &str, severity: Severity, description: &str) -> Result<()> {
+    let changelog_file_path = format!("{path}/CHANGELOG.md");
+
+    let mut changelog = Changelog::read_file(&changelog_file_path).await?;
 
-    let _changelog = Changelog::read_file(&format!("{path}/CHANGELOG.md")).await?;
+    changelog.push_description(severity, description)?;
+    changelog.write_file(&changelog_file_path).await?;
+    changelog.sync_cargo_toml(path).await?;
+    changelog.sync_dependencies(path).await?;
 
-    todo!("Implement changelog updates");
+    Ok(())
 }
 
 #[cfg(test)]
@@ -717,4 +785,80 @@ mod tests {
             "Unexpected prerelease line 9"
         );
     }
+
+    #[test]
+    fn push_description_prepends_dash_only_when_needed() {
+        let changelog_str = r"# Changelog
+
+## 0.2.0-git
+
+### Major
+
+- A change
+
+## 0.1.0
+
+<!-- Increment to skip CHANGELOG.md test: 0 -->
+";
+
+        let mut changelog = Changelog::parse(changelog_str).expect("Failed to parse changelog.");
+
+        changelog.push_description(Severity::Major, "testing no dash").unwrap();
+        changelog.push_description(Severity::Major, "- testing with dash").unwrap();
+
+        assert_eq!(
+            changelog.get_or_create_release_mut().contents.get(&Severity::Major).unwrap(),
+            &vec![
+                "- A change".to_string(),
+                "- testing no dash".to_string(),
+                "- testing with dash".to_string(),
+            ]
+        );
+    }
+
+    #[test]
+    fn get_or_create_release_mut_uses_first_when_prerelease() {
+        let changelog_str = r"# Changelog
+
+## 0.2.0-git
+
+### Major
+
+- A change
+
+## 0.1.0
+
+<!-- Increment to skip CHANGELOG.md test: 0 -->
+";
+
+        let mut changelog = Changelog::parse(changelog_str).expect("Failed to parse changelog.");
+
+        let current_release = changelog.get_or_create_release_mut();
+
+        assert_eq!(current_release.version, Version::parse("0.2.0-git").unwrap());
+    }
+
+    #[test]
+    fn get_or_create_release_mut_creates_new_when_current_is_released() {
+        let changelog_str = r"# Changelog
+
+## 0.2.0
+
+### Major
+
+- A change
+
+## 0.1.0
+
+<!-- Increment to skip CHANGELOG.md test: 0 -->
+";
+
+        let mut changelog = Changelog::parse(changelog_str).expect("Failed to parse changelog.");
+
+        let current_release = changelog.get_or_create_release_mut();
+
+        assert_eq!(current_release.version, Version::parse("0.2.1-git").unwrap());
+        // Assert the new release already inserted
+        assert_eq!(changelog.releases.len(), 3);
+    }
 }

crates/xtask/src/main.rs

@@ -299,7 +299,7 @@ impl Flags {
             MainCommand::Changelog(subcommand) => match subcommand.command {
                 ChangelogCommand::Ci => changelog::execute_ci().await,
                 ChangelogCommand::Change { path, severity, description } => {
-                    changelog::execute_change(&path, &severity, &description).await
+                    changelog::execute_change(&path, severity, &description).await
                 }
             },
         }