Add new remove_enum action

README.md

@@ -30,6 +30,7 @@ Designed for Postgres 12 and later.
 		- [Remove index](#remove-index)
 	- [Enums](#enums)
 		- [Create enum](#create-enum)
+		- [Remove enum](#remove-enum)
 - [Commands and options](#commands-and-options)
 	- [`reshape migrate`](#reshape-migrate)
 	- [`reshape complete`](#reshape-complete)
@@ -443,6 +444,8 @@ index = "name_idx"
 
 The `create_enum` action will create a new [enum type](https://www.postgresql.org/docs/current/datatype-enum.html) with the specified values.
 
+*Example: add a new `mood` enum type with three possible values*
+
 ```toml
 [[actions]]
 type = "create_enum"
@@ -450,6 +453,18 @@ name = "mood"
 values = ["happy", "ok", "sad"]
 ```
 
+#### Remove enum
+
+The `remove_enum` action will remove an existing [enum type](https://www.postgresql.org/docs/current/datatype-enum.html). Make sure all usages of the enum has been removed before running the migration. The enum will only be removed once the migration is completed.
+
+*Example: remove the `mood` enum type*
+
+```toml
+[[actions]]
+type = "remove_enum"
+enum = "mood"
+```
+
 ## Commands and options
 
 ### `reshape migrate`

src/migrations/mod.rs

@@ -36,6 +36,9 @@ pub use rename_table::RenameTable;
 mod create_enum;
 pub use create_enum::CreateEnum;
 
+mod remove_enum;
+pub use remove_enum::RemoveEnum;
+
 #[derive(Serialize, Deserialize, Debug)]
 pub struct Migration {
     pub name: String,

src/migrations/remove_enum.rs

@@ -0,0 +1,51 @@
+use super::{Action, MigrationContext};
+use crate::{
+    db::{Conn, Transaction},
+    schema::Schema,
+};
+use anyhow::Context;
+use serde::{Deserialize, Serialize};
+
+#[derive(Serialize, Deserialize, Debug)]
+pub struct RemoveEnum {
+    #[serde(rename = "enum")]
+    pub enum_name: String,
+}
+
+#[typetag::serde(name = "remove_enum")]
+impl Action for RemoveEnum {
+    fn describe(&self) -> String {
+        format!("Removing enum \"{}\"", self.enum_name)
+    }
+
+    fn run(
+        &self,
+        _ctx: &MigrationContext,
+        _db: &mut dyn Conn,
+        _schema: &Schema,
+    ) -> anyhow::Result<()> {
+        Ok(())
+    }
+
+    fn complete<'a>(
+        &self,
+        _ctx: &MigrationContext,
+        db: &'a mut dyn Conn,
+    ) -> anyhow::Result<Option<Transaction<'a>>> {
+        db.run(&format!(
+            r#"
+            DROP TYPE IF EXISTS {name}
+            "#,
+            name = self.enum_name,
+        ))
+        .context("failed to drop enum")?;
+
+        Ok(None)
+    }
+
+    fn update_schema(&self, _ctx: &MigrationContext, _schema: &mut Schema) {}
+
+    fn abort(&self, _ctx: &MigrationContext, _db: &mut dyn Conn) -> anyhow::Result<()> {
+        Ok(())
+    }
+}

tests/remove_enum.rs

@@ -0,0 +1,69 @@
+mod common;
+use common::Test;
+
+#[test]
+fn remove_enum() {
+    let mut test = Test::new("Remove enum");
+
+    test.first_migration(
+        r#"
+		name = "create_enum"
+
+		[[actions]]
+		type = "create_enum"
+		name = "mood"
+		values = ["happy", "ok", "sad"]
+		"#,
+    );
+
+    test.second_migration(
+        r#"
+		name = "remove_enum"
+
+		[[actions]]
+		type = "remove_enum"
+		enum = "mood"
+		"#,
+    );
+
+    test.after_first(|db| {
+        // Ensure enum was created
+        let enum_exists = !db
+            .query(
+                "
+				SELECT typname
+				FROM pg_catalog.pg_type
+				WHERE typcategory = 'E'
+				AND typname = 'mood'
+				",
+                &[],
+            )
+            .unwrap()
+            .is_empty();
+
+        assert!(enum_exists, "expected mood enum to have been created");
+    });
+
+    test.after_completion(|db| {
+        // Ensure enum was removed after completion
+        let enum_does_not_exist = db
+            .query(
+                "
+				SELECT typname
+				FROM pg_catalog.pg_type
+				WHERE typcategory = 'E'
+				AND typname = 'mood'
+				",
+                &[],
+            )
+            .unwrap()
+            .is_empty();
+
+        assert!(
+            enum_does_not_exist,
+            "expected mood enum to have been removed"
+        );
+    });
+
+    test.run();
+}