fix(filters): qualify model columns to avoid ambiguity with joins

Qualify plain model columns with the main table alias in resolvespec
filters so preload joins no longer cause SQLSTATE 42702, and accept
<table>.<column> from clients in resolvespec and restheadspec instead
of silently dropping the filter. Add join/preload tests for
resolvespec, restheadspec and funcspec.

pkg/common/qualify_column.go

@@ -0,0 +1,77 @@
+package common
+
+import (
+	"regexp"
+	"strings"
+
+	"github.com/bitechdev/ResolveSpec/pkg/reflection"
+)
+
+var rePlainIdent = regexp.MustCompile(`^[A-Za-z_][A-Za-z0-9_]*$`)
+
+// MainTableAlias returns the alias the main table gets in the SELECT:
+// the model's TableAlias() when provided, otherwise the bare table name.
+func MainTableAlias(model interface{}, tableName string) string {
+	if p, ok := model.(TableAliasProvider); ok {
+		if a := p.TableAlias(); a != "" {
+			return a
+		}
+	}
+	return reflection.ExtractTableNameOnly(tableName)
+}
+
+func isModelSQLColumn(model interface{}, column string) bool {
+	for _, c := range reflection.GetSQLModelColumns(model) {
+		if strings.EqualFold(c, column) {
+			return true
+		}
+	}
+	return false
+}
+
+// QualifyModelColumn returns "alias"."column" when column is a plain identifier
+// that exists on the model, so it stays unambiguous once joins are added.
+// Anything else (expressions, JSON paths, other tables' columns) is returned unchanged.
+func QualifyModelColumn(model interface{}, alias, column string) string {
+	if alias == "" || model == nil || !rePlainIdent.MatchString(column) || !isModelSQLColumn(model, column) {
+		return column
+	}
+	return QuoteIdent(alias) + "." + QuoteIdent(column)
+}
+
+// StripMainTablePrefix turns "<prefix>.<column>" into "<column>" when prefix is
+// one of the main table's names/aliases and column exists on the model.
+// Any other input is returned unchanged.
+func StripMainTablePrefix(model interface{}, column string, prefixes ...string) string {
+	idx := strings.Index(column, ".")
+	if idx <= 0 || model == nil {
+		return column
+	}
+	prefix := strings.Trim(column[:idx], `"`)
+	col := strings.Trim(column[idx+1:], `"`)
+	if !rePlainIdent.MatchString(prefix) || !rePlainIdent.MatchString(col) {
+		return column
+	}
+	for _, p := range prefixes {
+		if p != "" && strings.EqualFold(p, prefix) && isModelSQLColumn(model, col) {
+			return col
+		}
+	}
+	return column
+}
+
+// StripMainTablePrefixFromFilters applies StripMainTablePrefix to every filter column.
+func StripMainTablePrefixFromFilters(model interface{}, filters []FilterOption, prefixes ...string) {
+	for i := range filters {
+		filters[i].Column = StripMainTablePrefix(model, filters[i].Column, prefixes...)
+	}
+}
+
+// NormalizeMainTableFilters rewrites "<main table or alias>.<column>" filter
+// columns on opts to the bare model column (on a copy, never the caller's
+// slice) so the column validator keeps them.
+func NormalizeMainTableFilters(model interface{}, tableName string, opts *RequestOptions) {
+	opts.Filters = append([]FilterOption(nil), opts.Filters...)
+	StripMainTablePrefixFromFilters(model, opts.Filters,
+		MainTableAlias(model, tableName), reflection.ExtractTableNameOnly(tableName))
+}

pkg/common/qualify_column_test.go

@@ -0,0 +1,55 @@
+package common
+
+import "testing"
+
+type qualifyModel struct {
+	ID   int64  `bun:"id,pk"`
+	Name string `bun:"name"`
+}
+
+func TestQualifyModelColumn(t *testing.T) {
+	m := qualifyModel{}
+	cases := []struct{ alias, col, want string }{
+		{"t", "name", `"t"."name"`},
+		{"t", "NAME", `"t"."NAME"`},
+		{"t", "missing", "missing"},
+		{"t", "data->>'x'", "data->>'x'"},
+		{"t", "rel.name", "rel.name"},
+		{"", "name", "name"},
+	}
+	for _, c := range cases {
+		if got := QualifyModelColumn(m, c.alias, c.col); got != c.want {
+			t.Errorf("Qualify(%q,%q) = %q, want %q", c.alias, c.col, got, c.want)
+		}
+	}
+	if got := QualifyModelColumn(nil, "t", "name"); got != "name" {
+		t.Errorf("nil model: %q", got)
+	}
+}
+
+func TestStripMainTablePrefix(t *testing.T) {
+	m := qualifyModel{}
+	cases := []struct{ col, want string }{
+		{"province_state.name", "name"},
+		{`"province_state"."name"`, "name"},
+		{"PROVINCE_STATE.name", "name"},
+		{"rel_rid_country.name", "rel_rid_country.name"},
+		{"province_state.missing", "province_state.missing"},
+		{"name", "name"},
+	}
+	for _, c := range cases {
+		if got := StripMainTablePrefix(m, c.col, "province_state"); got != c.want {
+			t.Errorf("Strip(%q) = %q, want %q", c.col, got, c.want)
+		}
+	}
+}
+
+func TestStripMainTablePrefix_ValidatorKeepsFilter(t *testing.T) {
+	m := qualifyModel{}
+	filters := []FilterOption{{Column: "province_state.name", Operator: "eq", Value: "x"}}
+	StripMainTablePrefixFromFilters(m, filters, "province_state")
+	out := NewColumnValidator(m).FilterRequestOptions(RequestOptions{Filters: filters})
+	if len(out.Filters) != 1 || out.Filters[0].Column != "name" {
+		t.Fatalf("filters = %+v", out.Filters)
+	}
+}