Pre-commit hook to catch Validate() middleware functions being silently skipped

[echarrod]

Encore's validate feature, where a:

func (req myReq) Validation() error {

function is automatically is run by the middleware is very cool, but unfortunately it silently fails if the validate receiver function is a pointer, and the object passed to the API definition isn't (and vice versa) (from this Discord thread)

I wrote a pre-commit hook to try to catch this, as it unfortunately fails silently, so it might only be possible to tell if you write a test that you expect to fail, but it doesn't!

Script:

#!/usr/bin/env bash
# Check that Validate() receiver types match handler parameter types
# Encore only auto-calls Validate() when the types match:
#   Handler param *Type → Validate() receiver must be *Type
#   Handler param Type  → Validate() receiver must be Type

set -e

errors_found=0

echo "Checking for Validate() receiver type mismatches..."
echo ""

# Find all files with Validate() methods
validate_files=$(grep -rl "func (.*) Validate() error" src/givr --include="*.go" || true)

for file in $validate_files; do
   # Extract struct names that have Validate() methods and their receiver types
   # This will get lines like: "func (req *IssueCodeRequest) Validate()" or "func (req IssueCodeRequest) Validate()"
   validate_methods=$(grep -n "^func ([^)]*) Validate() error" "$file" || true)

   if [ -z "$validate_methods" ]; then
       continue
   fi

   while IFS= read -r validate_line; do
       # Extract whether it's a pointer receiver or value receiver
       # Pattern: func (varname *Type) or func (varname Type)

       # Get the full receiver part
       receiver=$(echo "$validate_line" | sed -n 's/.*func (\([^)]*\)) Validate().*/\1/p')

       # Check if it has a * (pointer receiver)
       if echo "$receiver" | grep -q '\*'; then
           # Pointer receiver - extract type name
           type_name=$(echo "$receiver" | sed 's/.*\*\([A-Za-z0-9_]*\).*/\1/')
           is_pointer_receiver=true
       else
           # Value receiver - extract type name
           type_name=$(echo "$receiver" | sed 's/.* \([A-Za-z0-9_]*\).*/\1/')
           is_pointer_receiver=false
       fi

       # Check if handler takes opposite type from Validate() receiver - that's an error
       if $is_pointer_receiver; then
           # Validate uses pointer receiver, so handler should take *Type
           # Check if handler takes value type instead of pointer (not preceded by *)
           # Use -A 10 to handle multi-line function signatures
           wrong_handler=$(grep -A 10 "//encore:api" "$file" | grep -E "[[:space:]]${type_name}[,)]" | grep -v "\*${type_name}" || true)
           if [ -n "$wrong_handler" ]; then
               echo "❌ MISMATCH in $file:"
               echo "   Validate() uses pointer receiver: *$type_name"
               echo "   But handler takes value parameter: $type_name"
               echo "   Line: $(echo "$validate_line" | cut -d: -f1)"
               echo ""
               errors_found=$((errors_found + 1))
           fi
       else
           # Validate uses value receiver, so handler should take Type (not *Type)
           # Check if handler takes pointer type instead of value
           wrong_handler=$(grep -A 10 "//encore:api" "$file" | grep -E "\*${type_name}[,)]" || true)
           if [ -n "$wrong_handler" ]; then
               echo "❌ MISMATCH in $file:"
               echo "   Validate() uses value receiver: $type_name"
               echo "   But handler takes pointer parameter: *$type_name"
               echo "   Line: $(echo "$validate_line" | cut -d: -f1)"
               echo ""
               errors_found=$((errors_found + 1))
           fi
       fi

   done <<< "$validate_methods"
done

if [ $errors_found -eq 0 ]; then
   echo "✅ All Validate() receiver types match their handler parameter types"
   exit 0
else
   echo ""
   echo "Found $errors_found mismatch(es)"
   echo ""
   echo "Remember: Encore only auto-calls Validate() when types match:"
   echo "  ✅ Handler: func(ctx, *Type) + Validate: func (r *Type) Validate()"
   echo "  ✅ Handler: func(ctx, Type)  + Validate: func (r Type) Validate()"
   echo "  ❌ Handler: func(ctx, Type)  + Validate: func (r *Type) Validate()"
   echo "  ❌ Handler: func(ctx, *Type) + Validate: func (r Type) Validate()"
   exit 1
fi

Add to your pre-commit config:

  - repo: local
    hooks:
      - id: check-validate-receivers
        name: Check Validate() receiver types match handler params
        entry: ./scripts/check-validate-receiver-match.sh
        language: script
        pass_filenames: false
        files: \.go$