Update bundled toml.abnf to TOML 1.1.0 and pin spec-corner behaviour (#1082)

* docs: update bundled toml.abnf to TOML 1.1.0

The bundled grammar was still the TOML 1.0.0 ABNF and also contained an
error that contradicted both the spec and the implementation. It is used
only as documentation (no code references it), but the README advertises
1.1.0 support, so the reference should match.

- non-eol: %x20-7F -> %x20-7E, so DEL (0x7F) is excluded from comments.
  The parser already rejects 0x7F in comments; the grammar was the only
  thing claiming otherwise.
- escape-seq-char: add \e (U+001B) and \xHH (#790, #796).
- partial-time: make seconds optional (#894).
- inline-table: allow whitespace/comments/newlines and a trailing comma
  (#904).

These four rules now match the official TOML 1.1.0 toml.abnf. All four
features were already implemented by the parser; this only corrects the
documentation.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

* test: pin spec-corner behaviour and TOML 1.1.0 features

Add native regression coverage for spec corners that the upstream
toml-test suite intentionally leaves undefined or under-tests, so a
future refactor cannot silently change behaviour while the generated
toml_testgen_test.go stays green:

- leap seconds (:60) rejected (not representable by time.Time);
- float overflow (1e400) rejected rather than decoded to +Inf
  (implementation-defined per #1058);
- fractional seconds without seconds rejected (#894);
- \xHH requires exactly two hex digits (#796);
- DEL (0x7F) rejected in comments and string bodies;
- multiline basic string quote-counting (content may end with up to two
  quotes).

Also keeps native coverage of the four 1.1.0 grammar features
(optional seconds, \e, \xHH, inline-table newlines/trailing commas)
independent of the generated suite.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: pelletier

compliance_corners_test.go

@@ -0,0 +1,95 @@
+package toml_test
+
+import (
+	"testing"
+
+	"github.com/pelletier/go-toml/v2"
+	"github.com/pelletier/go-toml/v2/internal/assert"
+)
+
+// This file pins go-toml's behaviour in TOML spec corners that the upstream
+// toml-test conformance suite intentionally leaves undefined or under-tests.
+// Without these, a future refactor could silently change behaviour while the
+// generated toml_testgen_test.go stays green.
+//
+// It also keeps native regression coverage for the four TOML 1.1.0 grammar
+// changes, independent of the generated suite.
+
+// TOML 1.1.0 grammar features that must be accepted.
+func TestCorners_TOML11Accepted(t *testing.T) {
+	cases := map[string]string{
+		// #894 — seconds are optional in time and datetime.
+		"local-time-no-seconds":      "x = 13:37\n",
+		"offset-datetime-no-seconds": "x = 1979-05-27T07:32Z\n",
+		"offset-datetime-no-sec-num": "x = 1979-05-27T07:32-07:00\n",
+		"local-datetime-no-seconds":  "x = 1979-05-27T07:32\n",
+		// #790 — \e is the escape character (U+001B).
+		"esc-e": "x = \"\\e\"\n",
+		// #796 — \xHH is a two-digit hex escape for codepoints <= 0xFF.
+		"esc-x-lower": "x = \"\\xff\"\n",
+		"esc-x-upper": "x = \"\\xFF\"\n",
+		// #904 — newlines and trailing commas in inline tables.
+		"inline-trailing-comma": "x = {a = 1,}\n",
+		"inline-newline":        "x = {\n\ta = 1,\n}\n",
+	}
+	for name, input := range cases {
+		t.Run(name, func(t *testing.T) {
+			var v map[string]interface{}
+			assert.NoError(t, toml.Unmarshal([]byte(input), &v))
+		})
+	}
+}
+
+// Gray-area corners where go-toml deliberately rejects input that the
+// conformance suite does not pin. These assertions document the intent.
+func TestCorners_DeliberateRejections(t *testing.T) {
+	cases := map[string]string{
+		// Leap seconds (:60) are grammar-permitted but not representable by
+		// time.Time without rolling over, so go-toml rejects them. toml-test
+		// only pins :61 as invalid, never :60.
+		"leap-second-local":  "x = 23:59:60\n",
+		"leap-second-offset": "x = 1979-05-27T23:59:60Z\n",
+
+		// Float overflow: 1e400 is rejected rather than decoded to +Inf.
+		// TOML 1.1.0 #1058 makes float size implementation-defined, so either
+		// behaviour is conformant; this pins go-toml's choice.
+		"float-overflow": "x = 1e400\n",
+
+		// #894 — fractional seconds may only appear when seconds are present.
+		"fraction-without-seconds": "x = 07:32.5\n",
+
+		// #796 — \xHH requires exactly two hex digits.
+		"esc-x-one-digit": "x = \"\\xf\"\n",
+		"esc-x-bad-hex":   "x = \"\\xg0\"\n",
+
+		// DEL (0x7F) is excluded from comments (non-eol = %x09 / %x20-7E /
+		// non-ascii) and from every string body.
+		"del-in-comment":   "x = 1 # a\x7fb\n",
+		"del-in-basic-str": "x = \"a\x7fb\"\n",
+
+		// #904 — a leading comma in an inline table is still invalid.
+		"inline-leading-comma": "x = {,a = 1}\n",
+	}
+	for name, input := range cases {
+		t.Run(name, func(t *testing.T) {
+			var v map[string]interface{}
+			assert.Error(t, toml.Unmarshal([]byte(input), &v))
+		})
+	}
+}
+
+// Multiline basic string quote-counting: content may end with up to two
+// quotation marks before the closing delimiter, but no more.
+func TestCorners_MultilineQuoteCounting(t *testing.T) {
+	t.Run("two-trailing-quotes", func(t *testing.T) {
+		var v struct {
+			X string `toml:"x"`
+		}
+		assert.NoError(t, toml.Unmarshal([]byte("x = \"\"\"a\"\"\"\"\"\n"), &v))
+		assert.Equal(t, `a""`, v.X)
+	})
+	t.Run("too-many-trailing-quotes", func(t *testing.T) {
+		var v map[string]interface{}
+		assert.Error(t, toml.Unmarshal([]byte("x = \"\"\"a\"\"\"\"\"\"\"\n"), &v))
+	})
+}

toml.abnf

@@ -36,7 +36,7 @@ newline =/ %x0D.0A  ; CRLF
 
 comment-start-symbol = %x23 ; #
 non-ascii = %x80-D7FF / %xE000-10FFFF
-non-eol = %x09 / %x20-7F / non-ascii
+non-eol = %x09 / %x20-7E / non-ascii
 
 comment = comment-start-symbol *non-eol
 
@@ -74,12 +74,14 @@ escape = %x5C                   ; \
 escape-seq-char =  %x22         ; "    quotation mark  U+0022
 escape-seq-char =/ %x5C         ; \    reverse solidus U+005C
 escape-seq-char =/ %x62         ; b    backspace       U+0008
+escape-seq-char =/ %x65         ; e    escape          U+001B
 escape-seq-char =/ %x66         ; f    form feed       U+000C
 escape-seq-char =/ %x6E         ; n    line feed       U+000A
 escape-seq-char =/ %x72         ; r    carriage return U+000D
 escape-seq-char =/ %x74         ; t    tab             U+0009
-escape-seq-char =/ %x75 4HEXDIG ; uXXXX                U+XXXX
-escape-seq-char =/ %x55 8HEXDIG ; UXXXXXXXX            U+XXXXXXXX
+escape-seq-char =/ %x78 2HEXDIG ; xHH                  U+00HH
+escape-seq-char =/ %x75 4HEXDIG ; uHHHH                U+HHHH
+escape-seq-char =/ %x55 8HEXDIG ; UHHHHHHHH            U+HHHHHHHH
 
 ;; Multiline Basic String
 
@@ -174,7 +176,7 @@ time-secfrac   = "." 1*DIGIT
 time-numoffset = ( "+" / "-" ) time-hour ":" time-minute
 time-offset    = "Z" / time-numoffset
 
-partial-time   = time-hour ":" time-minute ":" time-second [ time-secfrac ]
+partial-time   = time-hour ":" time-minute [ ":" time-second [ time-secfrac ] ]
 full-date      = date-fullyear "-" date-month "-" date-mday
 full-time      = partial-time time-offset
 
@@ -221,13 +223,14 @@ std-table-close = ws %x5D     ; ] Right square bracket
 
 ;; Inline Table
 
-inline-table = inline-table-open [ inline-table-keyvals ] inline-table-close
+inline-table = inline-table-open [ inline-table-keyvals ] ws-comment-newline inline-table-close
 
-inline-table-open  = %x7B ws     ; {
-inline-table-close = ws %x7D     ; }
-inline-table-sep   = ws %x2C ws  ; , Comma
+inline-table-open  = %x7B  ; {
+inline-table-close = %x7D  ; }
+inline-table-sep   = %x2C  ; , Comma
 
-inline-table-keyvals = keyval [ inline-table-sep inline-table-keyvals ]
+inline-table-keyvals =  ws-comment-newline keyval ws-comment-newline inline-table-sep inline-table-keyvals
+inline-table-keyvals =/ ws-comment-newline keyval ws-comment-newline [ inline-table-sep ]
 
 ;; Array Table