feat: Added create_database() to create a new database from a migrated template

Author: qfreewilll

src/asynchronous.rs

@@ -1,5 +1,5 @@
 use std::convert::TryInto;
-use std::path::Path;
+use std::path::{Path, PathBuf};
 use std::process::Stdio;
 use std::sync::{Arc, OnceLock};
 
@@ -115,6 +115,7 @@ pub(crate) async fn exec_create_db(
     port: u32,
     owner: &str,
     dbname: &str,
+    template_db: Option<&str>,
 ) -> TmpPostgrustResult<()> {
     let mut command = Command::new(createdb_bin);
     command
@@ -126,10 +127,35 @@ pub(crate) async fn exec_create_db(
         .arg("postgres")
         .arg("-O")
         .arg(owner)
+        .arg("--echo");
+    if let Some(template_db) = template_db {
+        command.arg("-T").arg(template_db);
+    }
+    command.arg(dbname);
+    cmd_as_non_root(&mut command);
+    exec_process(&mut command, TmpPostgrustError::CreateDBFailed).await
+}
+
+#[instrument]
+pub(crate) async fn exec_drop_db(
+    dropdb_bin: &Path,
+    socket: &Path,
+    port: u32,
+    dbname: &str,
+) -> TmpPostgrustResult<()> {
+    let mut command = Command::new(dropdb_bin);
+    command
+        .arg("-h")
+        .arg(socket)
+        .arg("-p")
+        .arg(port.to_string())
+        .arg("-U")
+        .arg("postgres")
+        .arg("--if-exists")
         .arg("--echo")
         .arg(dbname);
     cmd_as_non_root(&mut command);
-    exec_process(&mut command, TmpPostgrustError::CreateDBFailed).await
+    exec_process(&mut command, TmpPostgrustError::DropDBFailed).await
 }
 
 #[instrument]
@@ -199,6 +225,7 @@ pub struct ProcessGuard {
     pub(crate) _cache_directory: Arc<TempDir>,
     /// Socket directory for connection to the running process.
     pub(crate) socket_dir: Arc<TempDir>,
+    pub(crate) createdb_bin: PathBuf,
     pub(crate) postgres_process: Child,
     // Limit the total concurrent processes.
     pub(crate) _process_permit: SemaphorePermit<'static>,
@@ -224,17 +251,47 @@ impl ProcessGuard {
     /// Panics if a string file path cannot be obtained from the socket directory.
     #[must_use]
     pub fn connection_string(&self) -> String {
+        self.connection_string_for_db(&self.db_name)
+    }
+
+    /// Get a Postgresql format connection string for a database on this running instance.
+    ///
+    /// # Panics
+    ///
+    /// Panics if a string file path cannot be obtained from the socket directory.
+    #[must_use]
+    pub fn connection_string_for_db(&self, db_name: &str) -> String {
         format!(
             "postgresql:///?host={}&port={}&dbname={}&user={}",
             self.socket_dir
                 .path()
                 .to_str()
                 .expect("Failed to convert socket directory to a path"),
             self.port,
-            self.db_name,
+            db_name,
             self.user_name,
         )
     }
+
+    /// Create a new database in this running instance from the preserved template database.
+    ///
+    /// The returned connection string points at the newly-created database.
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if `createdb` fails to clone the template database.
+    pub async fn create_database(&self, db_name: &str) -> TmpPostgrustResult<String> {
+        exec_create_db(
+            &self.createdb_bin,
+            self.socket_dir.path(),
+            self.port,
+            &self.user_name,
+            db_name,
+            Some(crate::TMP_POSTGRUST_TEMPLATE_DB_NAME),
+        )
+        .await?;
+        Ok(self.connection_string_for_db(db_name))
+    }
 }
 
 fn cmd_as_non_root(command: &mut Command) {

src/errors.rs

@@ -46,6 +46,9 @@ pub enum TmpPostgrustError {
     /// Error when `createdb` fails to execute.
     #[error("createdb failed")]
     CreateDBFailed(ProcessCapture),
+    /// Error when `dropdb` fails to execute.
+    #[error("dropdb failed")]
+    DropDBFailed(ProcessCapture),
     /// Error when `postgresql.conf` cannot be written.
     #[error("failed to write postgresql.conf")]
     CreateConfigFailed(#[source] std::io::Error),