feat(dbml): @postgres/@sqlite dialect directives (#19)

Add parseable `@<namespace>[(<target>)]: <args>` directives embedded in DBML.
They are stored losslessly on each object's Metadata, round-trip unchanged
through the DBML writer, and are translated to SQL only by the writer for the
matching dialect.

- models: Directive type + catalog; Metadata map added to Column and Index
- dbml reader: parse and attach directives at database/table/column/index
  level; line-numbered errors; repeatable by default with singleton duplicate
  detection. Fixes a preexisting bug where an `indexes {}` closing brace ended
  the table early, dropping trailing Note: and directive lines.
- dbml writer: re-emit directives at their location; idempotent output
- pgsql writer: PARTITION BY / INHERITS / WITH / TABLESPACE (table),
  STORAGE / COMPRESSION / identity (column), WITH / TABLESPACE (index)
- sqlite writer: WITHOUT ROWID / STRICT (table), COLLATE (column)
- --strict-directives flag on ReaderOptions and WriterOptions
- docs/DBML_DIRECTIVES.md + reader/writer READMEs

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ss2MY5J11cRGwEz86ZXk7d

pkg/models/directives_test.go

@@ -0,0 +1,133 @@
+package models
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+func TestDirectiveKey(t *testing.T) {
+	cases := map[string]string{
+		"partition by RANGE (created_at)": "partition",
+		"WITHOUT ROWID":                   "without",
+		"  strict  ":                      "strict",
+		"":                                "",
+	}
+	for args, want := range cases {
+		if got := DirectiveKey(args); got != want {
+			t.Errorf("DirectiveKey(%q) = %q, want %q", args, got, want)
+		}
+	}
+}
+
+func TestAddDirectiveDerivesKey(t *testing.T) {
+	meta := map[string]any{}
+	AddDirective(meta, Directive{Namespace: "postgres", Args: "partition by RANGE (x)", Line: 2})
+	AddDirective(meta, Directive{Namespace: "postgres", Key: "tablespace", Args: "tablespace fast", Line: 3})
+
+	got := GetDirectives(meta)
+	if len(got) != 2 {
+		t.Fatalf("got %d directives, want 2", len(got))
+	}
+	if got[0].Key != "partition" {
+		t.Errorf("derived key = %q, want %q", got[0].Key, "partition")
+	}
+	if got[1].Key != "tablespace" {
+		t.Errorf("explicit key = %q, want %q", got[1].Key, "tablespace")
+	}
+}
+
+func TestAddDirectiveNilMeta(t *testing.T) {
+	// Must not panic.
+	AddDirective(nil, Directive{Namespace: "postgres", Args: "strict"})
+}
+
+func TestGetDirectivesOrdering(t *testing.T) {
+	meta := map[string]any{}
+	AddDirective(meta, Directive{Namespace: "sqlite", Args: "strict", Line: 9})
+	AddDirective(meta, Directive{Namespace: "postgres", Args: "with (b)", Line: 5})
+	AddDirective(meta, Directive{Namespace: "postgres", Args: "with (a)", Line: 5})
+	AddDirective(meta, Directive{Namespace: "postgres", Args: "partition by x", Line: 2})
+
+	got := GetDirectives(meta)
+	wantArgs := []string{"partition by x", "with (a)", "with (b)", "strict"}
+	if len(got) != len(wantArgs) {
+		t.Fatalf("got %d directives, want %d", len(got), len(wantArgs))
+	}
+	for i, w := range wantArgs {
+		if got[i].Args != w {
+			t.Errorf("directive[%d].Args = %q, want %q", i, got[i].Args, w)
+		}
+	}
+}
+
+func TestGetDirectivesTolerantDecodeAfterJSON(t *testing.T) {
+	meta := map[string]any{}
+	AddDirective(meta, Directive{Namespace: "postgres", Args: "partition by RANGE (created_at)", Line: 4})
+	AddDirective(meta, Directive{Namespace: "sqlite", Args: "without rowid", Line: 6})
+
+	blob, err := json.Marshal(meta)
+	if err != nil {
+		t.Fatalf("marshal: %v", err)
+	}
+	var round map[string]any
+	if err := json.Unmarshal(blob, &round); err != nil {
+		t.Fatalf("unmarshal: %v", err)
+	}
+
+	got := GetDirectives(round)
+	if len(got) != 2 {
+		t.Fatalf("got %d directives after JSON round-trip, want 2", len(got))
+	}
+	if got[0].Namespace != "postgres" || got[0].Key != "partition" || got[0].Line != 4 {
+		t.Errorf("post-JSON directive[0] = %+v", got[0])
+	}
+	if got[0].Args != "partition by RANGE (created_at)" {
+		t.Errorf("post-JSON args not verbatim: %q", got[0].Args)
+	}
+	if got[1].Namespace != "sqlite" || got[1].Key != "without" {
+		t.Errorf("post-JSON directive[1] = %+v", got[1])
+	}
+}
+
+func TestDirectivesForNamespaceAndHasDirective(t *testing.T) {
+	meta := map[string]any{}
+	AddDirective(meta, Directive{Namespace: "postgres", Args: "partition by x", Line: 1})
+	AddDirective(meta, Directive{Namespace: "sqlite", Args: "strict", Line: 2})
+
+	pg := DirectivesForNamespace(meta, "postgres")
+	if len(pg) != 1 || pg[0].Key != "partition" {
+		t.Errorf("DirectivesForNamespace(postgres) = %+v", pg)
+	}
+	if !HasDirective(meta, "sqlite", "strict") {
+		t.Error("HasDirective(sqlite, strict) = false, want true")
+	}
+	if HasDirective(meta, "postgres", "tablespace") {
+		t.Error("HasDirective(postgres, tablespace) = true, want false")
+	}
+}
+
+func TestDirectiveLocationAllowed(t *testing.T) {
+	if !DirectiveLocationAllowed("postgres", "partition", DirectiveLocationTable) {
+		t.Error("partition should be allowed at table level")
+	}
+	if DirectiveLocationAllowed("postgres", "partition", DirectiveLocationColumn) {
+		t.Error("partition should not be allowed at column level")
+	}
+	// Unknown directives are allowed everywhere so they can be preserved.
+	if !DirectiveLocationAllowed("postgres", "bogus", DirectiveLocationDatabase) {
+		t.Error("unknown key should be allowed everywhere")
+	}
+	if !DirectiveLocationAllowed("madeup", "x", DirectiveLocationTable) {
+		t.Error("unknown namespace should be allowed everywhere")
+	}
+}
+
+func TestFormatDirectiveLine(t *testing.T) {
+	d := Directive{Namespace: "postgres", Key: "identity", Args: "identity always"}
+	if got := FormatDirectiveLine(d, ""); got != "@postgres: identity always" {
+		t.Errorf("FormatDirectiveLine no target = %q", got)
+	}
+	if got := FormatDirectiveLine(d, "id"); got != "@postgres(id): identity always" {
+		t.Errorf("FormatDirectiveLine with target = %q", got)
+	}
+}