feat: add support for ignored_chars config to sqlx_core::migrate

sqlx-core/src/migrate/migration.rs

@@ -1,6 +1,5 @@
-use std::borrow::Cow;
-
 use sha2::{Digest, Sha384};
+use std::borrow::Cow;
 
 use super::MigrationType;
 
@@ -22,8 +21,26 @@ impl Migration {
         sql: Cow<'static, str>,
         no_tx: bool,
     ) -> Self {
-        let checksum = Cow::Owned(Vec::from(Sha384::digest(sql.as_bytes()).as_slice()));
+        let checksum = checksum(&sql);
+
+        Self::with_checksum(
+            version,
+            description,
+            migration_type,
+            sql,
+            checksum.into(),
+            no_tx,
+        )
+    }
 
+    pub(crate) fn with_checksum(
+        version: i64,
+        description: Cow<'static, str>,
+        migration_type: MigrationType,
+        sql: Cow<'static, str>,
+        checksum: Cow<'static, [u8]>,
+        no_tx: bool,
+    ) -> Self {
         Migration {
             version,
             description,
@@ -40,3 +57,39 @@ pub struct AppliedMigration {
     pub version: i64,
     pub checksum: Cow<'static, [u8]>,
 }
+
+pub fn checksum(sql: &str) -> Vec<u8> {
+    Vec::from(Sha384::digest(sql).as_slice())
+}
+
+pub fn checksum_fragments<'a>(fragments: impl Iterator<Item = &'a str>) -> Vec<u8> {
+    let mut digest = Sha384::new();
+
+    for fragment in fragments {
+        digest.update(fragment);
+    }
+
+    digest.finalize().to_vec()
+}
+
+#[test]
+fn fragments_checksum_equals_full_checksum() {
+    // Copied from `examples/postgres/axum-social-with-tests/migrations/3_comment.sql`
+    let sql = "\
+        create table comment (\r\n\
+            \tcomment_id uuid primary key default gen_random_uuid(),\r\n\
+            \tpost_id uuid not null references post(post_id),\r\n\
+            \tuser_id uuid not null references \"user\"(user_id),\r\n\
+            \tcontent text not null,\r\n\
+            \tcreated_at timestamptz not null default now()\r\n\
+        );\r\n\
+        \r\n\
+        create index on comment(post_id, created_at);\r\n\
+    ";
+
+    // Should yield a string for each character
+    let fragments_checksum = checksum_fragments(sql.split(""));
+    let full_checksum = checksum(sql);
+
+    assert_eq!(fragments_checksum, full_checksum);
+}

sqlx-core/src/migrate/migrator.rs

@@ -23,6 +23,8 @@ pub struct Migrator {
     pub locking: bool,
     #[doc(hidden)]
     pub no_tx: bool,
+    #[doc(hidden)]
+    pub table_name: Cow<'static, str>,
 }
 
 fn validate_applied_migrations(
@@ -51,6 +53,7 @@ impl Migrator {
         ignore_missing: false,
         no_tx: false,
         locking: true,
+        table_name: Cow::Borrowed("_sqlx_migrations"),
     };
 
     /// Creates a new instance with the given source.
@@ -81,6 +84,25 @@ impl Migrator {
         })
     }
 
+    /// Override the name of the table used to track executed migrations.
+    ///
+    /// May be schema-qualified and/or contain quotes. Defaults to `_sqlx_migrations`.
+    ///
+    /// Potentially useful for multi-tenant databases.
+    ///
+    /// ### Warning: Potential Data Loss or Corruption!
+    /// Changing this option for a production database will likely result in data loss or corruption
+    /// as the migration machinery will no longer be aware of what migrations have been applied
+    /// and will attempt to re-run them.
+    ///
+    /// You should create the new table as a copy of the existing migrations table (with contents!),
+    /// and be sure all instances of your application have been migrated to the new
+    /// table before deleting the old one.
+    pub fn dangerous_set_table_name(&mut self, table_name: impl Into<Cow<'static, str>>) -> &Self {
+        self.table_name = table_name.into();
+        self
+    }
+
     /// Specify whether applied migrations that are missing from the resolved migrations should be ignored.
     pub fn set_ignore_missing(&mut self, ignore_missing: bool) -> &Self {
         self.ignore_missing = ignore_missing;

sqlx-core/src/migrate/mod.rs

@@ -11,7 +11,7 @@ pub use migrate::{Migrate, MigrateDatabase};
 pub use migration::{AppliedMigration, Migration};
 pub use migration_type::MigrationType;
 pub use migrator::Migrator;
-pub use source::MigrationSource;
+pub use source::{MigrationSource, ResolveConfig, ResolveWith};
 
 #[doc(hidden)]
-pub use source::resolve_blocking;
+pub use source::{resolve_blocking, resolve_blocking_with_config};

sqlx-core/src/migrate/source.rs

@@ -1,8 +1,9 @@
 use crate::error::BoxDynError;
-use crate::migrate::{Migration, MigrationType};
+use crate::migrate::{migration, Migration, MigrationType};
 use futures_core::future::BoxFuture;
 
 use std::borrow::Cow;
+use std::collections::BTreeSet;
 use std::fmt::Debug;
 use std::fs;
 use std::io;
@@ -28,19 +29,48 @@ pub trait MigrationSource<'s>: Debug {
 
 impl<'s> MigrationSource<'s> for &'s Path {
     fn resolve(self) -> BoxFuture<'s, Result<Vec<Migration>, BoxDynError>> {
+        // Behavior changed from previous because `canonicalize()` is potentially blocking
+        // since it might require going to disk to fetch filesystem data.
+        self.to_owned().resolve()
+    }
+}
+
+impl MigrationSource<'static> for PathBuf {
+    fn resolve(self) -> BoxFuture<'static, Result<Vec<Migration>, BoxDynError>> {
+        // Technically this could just be `Box::pin(spawn_blocking(...))`
+        // but that would actually be a breaking behavior change because it would call
+        // `spawn_blocking()` on the current thread
         Box::pin(async move {
-            let canonical = self.canonicalize()?;
-            let migrations_with_paths =
-                crate::rt::spawn_blocking(move || resolve_blocking(&canonical)).await?;
+            crate::rt::spawn_blocking(move || {
+                let migrations_with_paths = resolve_blocking(&self)?;
 
-            Ok(migrations_with_paths.into_iter().map(|(m, _p)| m).collect())
+                Ok(migrations_with_paths.into_iter().map(|(m, _p)| m).collect())
+            })
+            .await
         })
     }
 }
 
-impl MigrationSource<'static> for PathBuf {
-    fn resolve(self) -> BoxFuture<'static, Result<Vec<Migration>, BoxDynError>> {
-        Box::pin(async move { self.as_path().resolve().await })
+/// A [`MigrationSource`] implementation with configurable resolution.
+/// 
+/// `S` may be `PathBuf`, `&Path` or any type that implements `Into<PathBuf>`.
+/// 
+/// See [`ResolveConfig`] for details.
+#[derive(Debug)]
+pub struct ResolveWith<S>(pub S, pub ResolveConfig);
+
+impl<'s, S: Debug + Into<PathBuf> + Send + 's> MigrationSource<'s> for ResolveWith<S> {
+    fn resolve(self) -> BoxFuture<'s, Result<Vec<Migration>, BoxDynError>> {
+        Box::pin(async move {
+            let path = self.0.into();
+            let config = self.1;
+
+            let migrations_with_paths =
+                crate::rt::spawn_blocking(move || resolve_blocking_with_config(&path, &config))
+                    .await?;
+
+            Ok(migrations_with_paths.into_iter().map(|(m, _p)| m).collect())
+        })
     }
 }
 
@@ -52,11 +82,87 @@ pub struct ResolveError {
     source: Option<io::Error>,
 }
 
+/// Configuration for migration resolution using [`ResolveWith`].
+#[derive(Debug, Default)]
+pub struct ResolveConfig {
+    ignored_chars: BTreeSet<char>,
+}
+
+impl ResolveConfig {
+    /// Return a default, empty configuration.
+    pub fn new() -> Self {
+        ResolveConfig {
+            ignored_chars: BTreeSet::new(),
+        }
+    }
+
+    /// Ignore a character when hashing migrations.
+    /// 
+    /// The migration SQL string itself will still contain the character,
+    /// but it will not be included when calculating the checksum.
+    /// 
+    /// This can be used to ignore whitespace characters so changing formatting
+    /// does not change the checksum.
+    /// 
+    /// Adding the same `char` more than once is a no-op.
+    /// 
+    /// ### Note: Changes Migration Checksum
+    /// This will change the checksum of resolved migrations, 
+    /// which may cause problems with existing deployments.
+    ///
+    /// **Use at your own risk.** 
+    pub fn ignore_char(&mut self, c: char) -> &mut Self {
+        self.ignored_chars.insert(c);
+        self
+    }
+
+    /// Ignore one or more characters when hashing migrations.
+    ///
+    /// The migration SQL string itself will still contain these characters,
+    /// but they will not be included when calculating the checksum.
+    ///
+    /// This can be used to ignore whitespace characters so changing formatting
+    /// does not change the checksum.
+    /// 
+    /// Adding the same `char` more than once is a no-op.
+    ///
+    /// ### Note: Changes Migration Checksum
+    /// This will change the checksum of resolved migrations, 
+    /// which may cause problems with existing deployments.
+    ///
+    /// **Use at your own risk.** 
+    pub fn ignore_chars(&mut self, chars: impl IntoIterator<Item = char>) -> &mut Self {
+        self.ignored_chars.extend(chars);
+        self
+    }
+
+    /// Iterate over the set of ignored characters.
+    /// 
+    /// Duplicate `char`s are not included.
+    pub fn ignored_chars(&self) -> impl Iterator<Item = char> + '_ {
+        self.ignored_chars.iter().copied()
+    }
+}
+
 // FIXME: paths should just be part of `Migration` but we can't add a field backwards compatibly
 // since it's `#[non_exhaustive]`.
+#[doc(hidden)]
 pub fn resolve_blocking(path: &Path) -> Result<Vec<(Migration, PathBuf)>, ResolveError> {
-    let s = fs::read_dir(path).map_err(|e| ResolveError {
-        message: format!("error reading migration directory {}: {e}", path.display()),
+    resolve_blocking_with_config(path, &ResolveConfig::new())
+}
+
+#[doc(hidden)]
+pub fn resolve_blocking_with_config(
+    path: &Path,
+    config: &ResolveConfig,
+) -> Result<Vec<(Migration, PathBuf)>, ResolveError> {
+    let path = path.canonicalize().map_err(|e| ResolveError {
+        message: format!("error canonicalizing path {}", path.display()),
+        source: Some(e),
+    })?;
+
+    let s = fs::read_dir(&path).map_err(|e| ResolveError {
+        message: format!("error reading migration directory {}", path.display()),
         source: Some(e),
     })?;
 
@@ -65,7 +171,7 @@ pub fn resolve_blocking(path: &Path) -> Result<Vec<(Migration, PathBuf)>, Resolv
     for res in s {
         let entry = res.map_err(|e| ResolveError {
             message: format!(
-                "error reading contents of migration directory {}: {e}",
+                "error reading contents of migration directory {}",
                 path.display()
             ),
             source: Some(e),
@@ -126,12 +232,15 @@ pub fn resolve_blocking(path: &Path) -> Result<Vec<(Migration, PathBuf)>, Resolv
         // opt-out of migration transaction
         let no_tx = sql.starts_with("-- no-transaction");
 
+        let checksum = checksum_with(&sql, &config.ignored_chars);
+
         migrations.push((
-            Migration::new(
+            Migration::with_checksum(
                 version,
                 Cow::Owned(description),
                 migration_type,
                 Cow::Owned(sql),
+                checksum.into(),
                 no_tx,
             ),
             entry_path,
@@ -143,3 +252,41 @@ pub fn resolve_blocking(path: &Path) -> Result<Vec<(Migration, PathBuf)>, Resolv
 
     Ok(migrations)
 }
+
+fn checksum_with(sql: &str, ignored_chars: &BTreeSet<char>) -> Vec<u8> {
+    if ignored_chars.is_empty() {
+        // This is going to be much faster because it doesn't have to UTF-8 decode `sql`.
+        return migration::checksum(sql);
+    }
+
+    migration::checksum_fragments(sql.split(|c| ignored_chars.contains(&c)))
+}
+
+#[test]
+fn checksum_with_ignored_chars() {
+    // Ensure that `checksum_with` returns the same digest for a given set of ignored chars
+    // as the equivalent string with the characters removed.
+    let ignored_chars = [' ', '\t', '\r', '\n'];
+
+    // Copied from `examples/postgres/axum-social-with-tests/migrations/3_comment.sql`
+    let sql = "\
+        create table comment (\r\n\
+            \tcomment_id uuid primary key default gen_random_uuid(),\r\n\
+            \tpost_id uuid not null references post(post_id),\r\n\
+            \tuser_id uuid not null references \"user\"(user_id),\r\n\
+            \tcontent text not null,\r\n\
+            \tcreated_at timestamptz not null default now()\r\n\
+        );\r\n\
+        \r\n\
+        create index on comment(post_id, created_at);\r\n\
+    ";
+
+    let stripped_sql = sql.replace(&ignored_chars[..], "");
+
+    let ignored_chars = BTreeSet::from(ignored_chars);
+
+    let digest_ignored = checksum_with(sql, &ignored_chars);
+    let digest_stripped = migration::checksum(&stripped_sql);
+
+    assert_eq!(digest_ignored, digest_stripped);
+}