1 files changed, 62 insertions, 0 deletions
diff --git a/languages/go/claude/hooks/validate-go.sh b/languages/go/claude/hooks/validate-go.sh
new file mode 100755
index 0000000..c2c6ff1
--- /dev/null
+++ b/languages/go/claude/hooks/validate-go.sh
@@ -0,0 +1,62 @@
+#!/usr/bin/env bash
+# Validate Go files after Edit/Write/MultiEdit.
+# PostToolUse hook: receives tool-call JSON on stdin.
+#
+# On success: exit 0 silent.
+# On failure: emit JSON with hookSpecificOutput.additionalContext so Claude
+# sees a structured error in its context, THEN exit 2 to block the tool
+# pipeline. stderr still echoes the error for terminal visibility.
+#
+# Phase 1: gofmt — formatting must be clean.
+# Phase 2: go vet — compile + suspicious-construct check on the file's package,
+#          run only when the file sits inside a module (go.mod found). go vet
+#          type-checks, so it surfaces compile and syntax errors too.
+#
+# Tests deliberately stop here: `go test` on the edited package can pull in slow
+# or integration-tagged tests that shouldn't fire on every keystroke. Run them
+# explicitly via `make coverage` / `go test`.
+
+set -u
+
+# Emit a JSON failure payload and exit 2. Arguments:
+#   $1 — short failure type (e.g. "GO VET FAILED")
+#   $2 — file path
+#   $3 — tool output (error body)
+fail_json() {
+    local ctx
+    ctx="$(printf '%s: %s\n\n%s\n\nFix before proceeding.' "$1" "$2" "$3" \
+        | jq -Rs .)"
+    cat <<EOF
+{"hookSpecificOutput": {"hookEventName": "PostToolUse", "additionalContext": $ctx}}
+EOF
+    printf '%s: %s\n%s\n' "$1" "$2" "$3" >&2
+    exit 2
+}
+
+f="$(jq -r '.tool_input.file_path // .tool_response.filePath // empty')"
+[ -z "$f" ] && exit 0
+[ "${f##*.}" = "go" ] || exit 0
+[ -f "$f" ] || exit 0
+
+# No toolchain on this machine — nothing to validate, don't block the edit.
+command -v gofmt >/dev/null 2>&1 || exit 0
+
+# --- Phase 1: formatting ---
+# gofmt -l prints the path when the file isn't gofmt-clean (and stays silent on
+# a parse error — go vet catches those in Phase 2). Show the diff so the fix is
+# obvious.
+if [ -n "$(gofmt -l "$f" 2>/dev/null)" ]; then
+    fail_json "GOFMT: file is not gofmt-clean" "$f" "$(gofmt -d "$f" 2>&1)"
+fi
+
+# --- Phase 2: vet (needs module context) ---
+command -v go >/dev/null 2>&1 || exit 0
+dir="$(dirname "$f")"
+gomod="$(cd "$dir" && go env GOMOD 2>/dev/null)"
+if [ -n "$gomod" ] && [ "$gomod" != "/dev/null" ]; then
+    if ! out="$(cd "$dir" && go vet . 2>&1)"; then
+        fail_json "GO VET FAILED" "$f" "$out"
+    fi
+fi
+
+exit 0