Fix checksum formatting in ME

This is to align with other tools, for example the CLI shasum utility on
linux.

The old format is still recognized and accepted for compatibility with
existing migration tables.

closes #1887

migration-engine/connectors/migration-connector/src/lib.rs

@@ -93,11 +93,17 @@ fn checksum(script: &str) -> String {
     checksum.format_checksum()
 }
 
+/// The length (in bytes, or equivalently ascii characters) of the checksum
+/// strings.
+const CHECKSUM_STR_LEN: usize = 64;
+
 /// Format a checksum to a hexadecimal string. This is used to checksum
 /// migration scripts with Sha256.
 pub trait FormatChecksum {
     /// Format a checksum to a hexadecimal string.
     fn format_checksum(&self) -> String;
+    /// Obsolete checksum method, should only be used for compatibility.
+    fn format_checksum_old(&self) -> String;
 }
 
 impl FormatChecksum for [u8; 32] {
@@ -106,10 +112,41 @@ impl FormatChecksum for [u8; 32] {
 
         let mut checksum_string = String::with_capacity(32 * 2);
 
+        for byte in self {
+            write!(checksum_string, "{:02x}", byte).unwrap();
+        }
+
+        assert_eq!(checksum_string.len(), CHECKSUM_STR_LEN);
+
+        checksum_string
+    }
+
+    // Due to an omission in a previous version of the migration engine,
+    // some migrations tables will have old migrations with checksum strings
+    // that have not been zero-padded.
+    //
+    // Corresponding issue:
+    // https://github.com/prisma/prisma-engines/issues/1887
+    fn format_checksum_old(&self) -> String {
+        use std::fmt::Write as _;
+
+        let mut checksum_string = String::with_capacity(32 * 2);
+
         for byte in self {
             write!(checksum_string, "{:x}", byte).unwrap();
         }
 
         checksum_string
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn format_checksum_does_not_strip_zeros() {
+        assert_eq!(checksum("hello"), "2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824");
+        assert_eq!(checksum("abcd").len(), CHECKSUM_STR_LEN);
+    }
+}

migration-engine/connectors/migration-connector/src/migrations_directory.rs

@@ -5,7 +5,7 @@
 //! It also contains multiple subfolders, named after the migration id, and each containing:
 //! - A migration script
 
-use crate::{ConnectorError, ConnectorResult, FormatChecksum};
+use crate::{CHECKSUM_STR_LEN, ConnectorError, ConnectorResult, FormatChecksum};
 use sha2::{Digest, Sha256, Sha512};
 use std::{
     error::Error,
@@ -221,7 +221,19 @@ impl MigrationDirectory {
         hasher.update(&filesystem_script);
         let filesystem_script_checksum: [u8; 32] = hasher.finalize().into();
 
-        Ok(checksum_str == filesystem_script_checksum.format_checksum())
+        // Due to an omission in a previous version of the migration engine,
+        // some migrations tables will have old migrations with checksum strings
+        // that have not been zero-padded.
+        //
+        // Corresponding issue:
+        // https://github.com/prisma/prisma-engines/issues/1887
+        let filesystem_script_checksum_str = if checksum_str.len() > 0 && checksum_str.len() != CHECKSUM_STR_LEN {
+            filesystem_script_checksum.format_checksum_old()
+        } else {
+            filesystem_script_checksum.format_checksum()
+        };
+
+        Ok(checksum_str == filesystem_script_checksum_str)
     }
 
     /// Write the migration script to the directory.