sqlctemplate: Error on template-like artifacts that are probably mistakes

rivershared/sqlctemplate/sqlc_template.go

@@ -97,6 +97,12 @@ var (
 	templateRE         = regexp.MustCompile(`/\* TEMPLATE: (.*?) \*/`)
 )
 
+// Regex to search for in SQL after replacement has occurred and which probably
+// represents a syntax error. sqlctemplate isn't a true compiler so if template
+// REs don't match, we can be left with some subtle bugs where there's some
+// minor problem like a missing semicolon that are hard to debug.
+var postReplaceMistakeRE = regexp.MustCompile(`\/\*\s*TEMPLATE([A-Z0-9_]+)?`) // also finds "/* TEMPLATE_BEGIN"
+
 // Run replaces any tempates in input SQL with values from context added via
 // WithReplacements.
 //
@@ -189,6 +195,11 @@ func (r *Replacer) RunSafely(ctx context.Context, sql string, args []any) (strin
 		return "", nil, errors.New("sqlctemplate params present in SQL but missing in context: " + strings.Join(templatesMissing, ", "))
 	}
 
+	probableMistakes := postReplaceMistakeRE.FindAllString(updatedSQL, -1)
+	if len(probableMistakes) > 0 {
+		return "", nil, errors.New("sqlctemplate found template-like tag after replacements; probably syntax error or missing end tag: " + strings.Join(probableMistakes, ", "))
+	}
+
 	if len(container.NamedArgs) > 0 {
 		placeholderNum := len(args)
 

rivershared/sqlctemplate/sqlc_template_test.go

@@ -115,6 +115,53 @@ func TestReplacer(t *testing.T) {
 		`, updatedSQL)
 	})
 
+	t.Run("SyntaxMistakes", func(t *testing.T) {
+		t.Parallel()
+
+		replacer, _ := setup(t)
+
+		// Missing colon after "TEMPLATE".
+		{
+			ctx := WithReplacements(ctx, map[string]Replacement{}, nil)
+
+			_, _, err := replacer.RunSafely(ctx, `
+			-- name: JobCountByState :one
+			SELECT count(*)
+			FROM /* TEMPLATE schema */river_job
+			WHERE state = @state;
+		`, nil)
+			require.EqualError(t, err, "sqlctemplate found template-like tag after replacements; probably syntax error or missing end tag: /* TEMPLATE")
+		}
+
+		// Missing "TEMPLATE_END".
+		{
+			ctx := WithReplacements(ctx, map[string]Replacement{}, nil)
+
+			_, _, err := replacer.RunSafely(ctx, `
+			-- name: JobCountByState :one
+			SELECT count(*)
+			FROM /* TEMPLATE_BEGIN: schema */river_job
+			WHERE state = @state;
+		`, nil)
+			require.EqualError(t, err, "sqlctemplate found template-like tag after replacements; probably syntax error or missing end tag: /* TEMPLATE_BEGIN")
+		}
+
+		// Extra whitespace before "TEMPLATE".
+		{
+			ctx := WithReplacements(ctx, map[string]Replacement{
+				"state": {Value: "'available'"},
+			}, nil)
+
+			_, _, err := replacer.RunSafely(ctx, `
+			-- name: JobCountByState :one
+			SELECT count(*)
+			FROM /*   TEMPLATE schema */river_job
+			WHERE state = /* TEMPLATE_BEGIN: state */ 'available' /* TEMPLATE_END */ -- need to have one valid template to get to the right error
+		`, nil)
+			require.EqualError(t, err, "sqlctemplate found template-like tag after replacements; probably syntax error or missing end tag: /*   TEMPLATE")
+		}
+	})
+
 	t.Run("RepeatedTemplate", func(t *testing.T) {
 		t.Parallel()