diff --git a/src/SUMMARY.md b/src/SUMMARY.md index 977ad581e..66ea9776f 100644 --- a/src/SUMMARY.md +++ b/src/SUMMARY.md @@ -8,6 +8,7 @@ - [Input format](input-format.md) - [Keywords](keywords.md) - [Identifiers](identifiers.md) + - [Frontmatter](frontmatter.md) - [Comments](comments.md) - [Whitespace](whitespace.md) - [Tokens](tokens.md) diff --git a/src/frontmatter.md b/src/frontmatter.md new file mode 100644 index 000000000..ba6609292 --- /dev/null +++ b/src/frontmatter.md @@ -0,0 +1,43 @@ +r[frontmatter] +# Frontmatter + +r[frontmatter.syntax] +```grammar,lexer +@root FRONTMATTER -> + FRONTMATTER_FENCE HORIZONTAL_WHITESPACE* INFOSTRING? HORIZONTAL_WHITESPACE* LF + (FRONTMATTER_LINE LF )* + FRONTMATTER_FENCE[^matched-fence] HORIZONTAL_WHITESPACE* LF + +FRONTMATTER_FENCE -> `---` `-`* + +INFOSTRING -> (XID_Start | `_`) ( XID_Continue | `-` | `.` )* + +FRONTMATTER_LINE -> (~INVALID_FRONTMATTER_LINE_START (~INVALID_FRONTMATTER_LINE_CONTINUE)*)? + +INVALID_FRONTMATTER_LINE_START -> (FRONTMATTER_FENCE[^escaped-fence] | LF) + +INVALID_FRONTMATTER_LINE_CONTINUE -> LF +``` + +[^matched-fence]: The closing fence must have the same number of `-` as the opening fence +[^escaped-fence]: A `FRONTMATTER_FENCE` at the beginning of a `FRONTMATTER_LINE` is only invalid if it has the same or more `-` as the `FRONTMATTER_FENCE` + +Frontmatter is an optional section for content intended for external tools without requiring these tools to have full knowledge of the Rust grammar. + +r[frontmatter.document] +Frontmatter may only be preceded by a [shebang] and whitespace. + +r[frontmatter.fence] +The delimiters are referred to as a "fence." +The opening and closing fences must be at the start of a line. +They must be a matching pair of three or more hyphens (`-`). +A fence may be followed by horizontal whitespace. + +r[frontmatter.infostring] +Following the opening fence may be an infostring for identifying the intention of the contained content. +An infostring may be followed by horizontal whitespace. + +r[frontmatter.body] +The body of the frontmatter may contain any content except for a line starting with as many or more hyphens (`-`) than in the fences. + +[shebang]: input-format.md#shebang-removal diff --git a/src/whitespace.md b/src/whitespace.md index b398d0c95..1e446470f 100644 --- a/src/whitespace.md +++ b/src/whitespace.md @@ -4,23 +4,32 @@ r[lex.whitespace] r[whitespace.syntax] ```grammar,lexer @root WHITESPACE -> - U+0009 // Horizontal tab, `'\t'` - | U+000A // Line feed, `'\n'` - | U+000B // Vertical tab - | U+000C // Form feed - | U+000D // Carriage return, `'\r'` - | U+0020 // Space, `' '` - | U+0085 // Next line - | U+200E // Left-to-right mark - | U+200F // Right-to-left mark - | U+2028 // Line separator - | U+2029 // Paragraph separator - -TAB -> U+0009 // Horizontal tab, `'\t'` - -LF -> U+000A // Line feed, `'\n'` - -CR -> U+000D // Carriage return, `'\r'` + END_OF_LINE + | IGNORABLE_CODE_POINT + | HORIZONTAL_WHITESPACE + +END_OF_LINE -> + LF + | U+000B // vertical tabulation + | U+000C // form feed + | CR + | U+0085 // Unicode next line + | U+2028 // Unicode LINE SEPARATOR + | U+2029 // Unicode PARAGRAPH SEPARATOR + +IGNORABLE_CODE_POINT -> + U+200E // Unicode LEFT-TO-RIGHT MARK + | U+200F // Unicode RIGHT-TO-LEFT MARK + +HORIZONTAL_WHITESPACE -> + TAB + | U+0020 // space ' ' + +TAB -> U+0009 // horizontal tab ('\t') + +LF -> U+000A // line feed ('\n') + +CR -> U+000D // carriage return ('\r') ``` r[lex.whitespace.intro]