These are the supported markdown parsing extensions. OR these values together to select multiple extensions.
const (
NoExtensions Extensions = 0
NoIntraEmphasis Extensions = 1 << iota // Ignore emphasis markers inside words
Tables // Render tables
FencedCode // Render fenced code blocks
Autolink // Detect embedded URLs that are not explicitly marked
Strikethrough // Strikethrough text using ~~test~~
LaxHTMLBlocks // Loosen up HTML block parsing rules
SpaceHeadings // Be strict about prefix heading rules
HardLineBreak // Translate newlines into line breaks
TabSizeEight // Expand tabs to eight spaces instead of four
Footnotes // Pandoc-style footnotes
NoEmptyLineBeforeBlock // No need to insert an empty line to start a (code, quote, ordered list, unordered list) block
HeadingIDs // specify heading IDs with {#id}
Titleblock // Titleblock ala pandoc
AutoHeadingIDs // Create the heading ID from the text
BackslashLineBreak // Translate trailing backslashes into line breaks
DefinitionLists // Render definition lists
CommonHTMLFlags HTMLFlags = UseXHTML | Smartypants |
SmartypantsFractions | SmartypantsDashes | SmartypantsLatexDashes
CommonExtensions Extensions = NoIntraEmphasis | Tables | FencedCode |
Autolink | Strikethrough | SpaceHeadings | HeadingIDs |
BackslashLineBreak | DefinitionLists
)
The size of a tab stop.
const (
TabSizeDefault = 4
TabSizeDouble = 8
)
Version string of the package. Appears in the rendered document when CompletePage flag is on.
const Version = "2.0"
func Run(input []byte, opts ...Option) []byte
Run is the main entry point to Blackfriday. It parses and renders a block of markdown-encoded text.
The simplest invocation of Run takes one argument, input:
output := Run(input)
This will parse the input with CommonExtensions enabled and render it with the default HTMLRenderer (with CommonHTMLFlags).
Variadic arguments opts can customize the default behavior. Since Markdown type does not contain exported fields, you can not use it directly. Instead, use the With* functions. For example, this will call the most basic functionality, with no extensions:
output := Run(input, WithNoExtensions())
You can use any number of With* arguments, even contradicting ones. They will be applied in order of appearance and the latter will override the former:
output := Run(input, WithNoExtensions(), WithExtensions(exts),
WithRenderer(yourRenderer))
func SanitizedAnchorName(text string) string
SanitizedAnchorName returns a sanitized anchor name for the given text.
It implements the algorithm specified in the package comment.
CellAlignFlags holds a type of alignment in a table cell.
type CellAlignFlags int
These are the possible flag values for the table cell renderer. Only a single one of these values will be used; they are not ORed together. These are mostly of interest if you are writing a new output format.
const (
TableAlignmentLeft CellAlignFlags = 1 << iota
TableAlignmentRight
TableAlignmentCenter = (TableAlignmentLeft | TableAlignmentRight)
)
CodeBlockData contains fields relevant to a CodeBlock node type.
type CodeBlockData struct {
IsFenced bool // Specifies whether it's a fenced code block or an indented one
Info []byte // This holds the info string
FenceChar byte
FenceLength int
FenceOffset int
}
Extensions is a bitwise or'ed collection of enabled Blackfriday's extensions.
type Extensions int
HTMLFlags control optional behavior of HTML renderer.
type HTMLFlags int
HTML renderer configuration options.
const (
HTMLFlagsNone HTMLFlags = 0
SkipHTML HTMLFlags = 1 << iota // Skip preformatted HTML blocks
SkipImages // Skip embedded images
SkipLinks // Skip all links
Safelink // Only link to trusted protocols
NofollowLinks // Only link with rel="nofollow"
NoreferrerLinks // Only link with rel="noreferrer"
NoopenerLinks // Only link with rel="noopener"
HrefTargetBlank // Add a blank target
CompletePage // Generate a complete HTML page
UseXHTML // Generate XHTML output instead of HTML
FootnoteReturnLinks // Generate a link at the end of a footnote to return to the source
Smartypants // Enable smart punctuation substitutions
SmartypantsFractions // Enable smart fractions (with Smartypants)
SmartypantsDashes // Enable smart dashes (with Smartypants)
SmartypantsLatexDashes // Enable LaTeX-style dashes (with Smartypants)
SmartypantsAngledQuotes // Enable angled double quotes (with Smartypants) for double quotes rendering
SmartypantsQuotesNBSP // Enable « French guillemets » (with Smartypants)
TOC // Generate a table of contents
)
HTMLRenderer is a type that implements the Renderer interface for HTML output.
Do not create this directly, instead use the NewHTMLRenderer function.
type HTMLRenderer struct {
HTMLRendererParameters
// contains filtered or unexported fields
}
func NewHTMLRenderer(params HTMLRendererParameters) *HTMLRenderer
NewHTMLRenderer creates and configures an HTMLRenderer object, which satisfies the Renderer interface.
func (r *HTMLRenderer) RenderFooter(w io.Writer, ast *Node)
RenderFooter writes HTML document footer.
func (r *HTMLRenderer) RenderHeader(w io.Writer, ast *Node)
RenderHeader writes HTML document preamble and TOC if requested.
func (r *HTMLRenderer) RenderNode(w io.Writer, node *Node, entering bool) WalkStatus
RenderNode is a default renderer of a single node of a syntax tree. For block nodes it will be called twice: first time with entering=true, second time with entering=false, so that it could know when it's working on an open tag and when on close. It writes the result to w.
The return value is a way to tell the calling walker to adjust its walk pattern: e.g. it can terminate the traversal by returning Terminate. Or it can ask the walker to skip a subtree of this node by returning SkipChildren. The typical behavior is to return GoToNext, which asks for the usual traversal to the next node.
HTMLRendererParameters is a collection of supplementary parameters tweaking the behavior of various parts of HTML renderer.
type HTMLRendererParameters struct {
// Prepend this text to each relative URL.
AbsolutePrefix string
// Add this text to each footnote anchor, to ensure uniqueness.
FootnoteAnchorPrefix string
// Show this text inside the <a> tag for a footnote return link, if the
// HTML_FOOTNOTE_RETURN_LINKS flag is enabled. If blank, the string
// <sup>[return]</sup> is used.
FootnoteReturnLinkContents string
// If set, add this text to the front of each Heading ID, to ensure
// uniqueness.
HeadingIDPrefix string
// If set, add this text to the back of each Heading ID, to ensure uniqueness.
HeadingIDSuffix string
// Increase heading levels: if the offset is 1, <h1> becomes <h2> etc.
// Negative offset is also valid.
// Resulting levels are clipped between 1 and 6.
HeadingLevelOffset int
Title string // Document title (used if CompletePage is set)
CSS string // Optional CSS file URL (used if CompletePage is set)
Icon string // Optional icon file URL (used if CompletePage is set)
Flags HTMLFlags // Flags allow customizing this renderer's behavior
}
HeadingData contains fields relevant to a Heading node type.
type HeadingData struct {
Level int // This holds the heading level number
HeadingID string // This might hold heading ID, if present
IsTitleblock bool // Specifies whether it's a title block
}
LinkData contains fields relevant to a Link node type.
type LinkData struct {
Destination []byte // Destination is what goes into a href
Title []byte // Title is the tooltip thing that goes in a title attribute
NoteID int // NoteID contains a serial number of a footnote, zero if it's not a footnote
Footnote *Node // If it's a footnote, this is a direct link to the footnote Node. Otherwise nil.
}
ListData contains fields relevant to a List and Item node type.
type ListData struct {
ListFlags ListType
Tight bool // Skip <p>s around list item data if true
BulletChar byte // '*', '+' or '-' in bullet lists
Delimiter byte // '.' or ')' after the number in ordered lists
RefLink []byte // If not nil, turns this list item into a footnote item and triggers different rendering
IsFootnotesList bool // This is a list of footnotes
}
ListType contains bitwise or'ed flags for list and list item objects.
type ListType int
These are the possible flag values for the ListItem renderer. Multiple flag values may be ORed together. These are mostly of interest if you are writing a new output format.
const (
ListTypeOrdered ListType = 1 << iota
ListTypeDefinition
ListTypeTerm
ListItemContainsBlock
ListItemBeginningOfList // TODO: figure out if this is of any use now
ListItemEndOfList
)
Markdown is a type that holds extensions and the runtime state used by Parse, and the renderer. You can not use it directly, construct it with New.
type Markdown struct {
// contains filtered or unexported fields
}
func New(opts ...Option) *Markdown
New constructs a Markdown processor. You can use the same With* functions as for Run() to customize parser's behavior and the renderer.
func (p *Markdown) Parse(input []byte) *Node
Parse is an entry point to the parsing part of Blackfriday. It takes an input markdown document and produces a syntax tree for its contents. This tree can then be rendered with a default or custom renderer, or analyzed/transformed by the caller to whatever non-standard needs they have. The return value is the root node of the syntax tree.
Node is a single element in the abstract syntax tree of the parsed document. It holds connections to the structurally neighboring nodes and, for certain types of nodes, additional information that might be needed when rendering.
type Node struct {
Type NodeType // Determines the type of the node
Parent *Node // Points to the parent
FirstChild *Node // Points to the first child, if any
LastChild *Node // Points to the last child, if any
Prev *Node // Previous sibling; nil if it's the first child
Next *Node // Next sibling; nil if it's the last child
Literal []byte // Text contents of the leaf nodes
HeadingData // Populated if Type is Heading
ListData // Populated if Type is List
CodeBlockData // Populated if Type is CodeBlock
LinkData // Populated if Type is Link
TableCellData // Populated if Type is TableCell
// contains filtered or unexported fields
}
func NewNode(typ NodeType) *Node
NewNode allocates a node of a specified type.
func (n *Node) AppendChild(child *Node)
AppendChild adds a node 'child' as a child of 'n'. It panics if either node is nil.
func (n *Node) InsertBefore(sibling *Node)
InsertBefore inserts 'sibling' immediately before 'n'. It panics if either node is nil.
func (n *Node) IsContainer() bool
IsContainer returns true if 'n' can contain children.
func (n *Node) IsLeaf() bool
IsLeaf returns true if 'n' is a leaf node.
func (n *Node) String() string
func (n *Node) Unlink()
Unlink removes node 'n' from the tree. It panics if the node is nil.
func (n *Node) Walk(visitor NodeVisitor)
Walk is a convenience method that instantiates a walker and starts a traversal of subtree rooted at n.
NodeType specifies a type of a single node of a syntax tree. Usually one node (and its type) corresponds to a single markdown feature, e.g. emphasis or code block.
type NodeType int
Constants for identifying different types of nodes. See NodeType.
const (
Document NodeType = iota
BlockQuote
List
Item
Paragraph
Heading
HorizontalRule
Emph
Strong
Del
Link
Image
Text
HTMLBlock
CodeBlock
Softbreak
Hardbreak
Code
HTMLSpan
Table
TableCell
TableHead
TableBody
TableRow
)
func (t NodeType) String() string
NodeVisitor is a callback to be called when traversing the syntax tree. Called twice for every node: once with entering=true when the branch is first visited, then with entering=false after all the children are done.
type NodeVisitor func(node *Node, entering bool) WalkStatus
Option customizes the Markdown processor's default behavior.
type Option func(*Markdown)
func WithExtensions(e Extensions) Option
WithExtensions allows you to pick some of the many extensions provided by Blackfriday. You can bitwise OR them.
func WithNoExtensions() Option
WithNoExtensions turns off all extensions and custom behavior.
func WithRefOverride(o ReferenceOverrideFunc) Option
WithRefOverride sets an optional function callback that is called every time a reference is resolved.
In Markdown, the link reference syntax can be made to resolve a link to a reference instead of an inline URL, in one of the following ways:
Usually, the refid is defined at the bottom of the Markdown document. If this override function is provided, the refid is passed to the override function first, before consulting the defined refids at the bottom. If the override function indicates an override did not occur, the refids at the bottom will be used to fill in the link details.
func WithRenderer(r Renderer) Option
WithRenderer allows you to override the default renderer.
Reference represents the details of a link. See the documentation in Options for more details on use-case.
type Reference struct {
// Link is usually the URL the reference points to.
Link string
// Title is the alternate text describing the link in more detail.
Title string
// Text is the optional text to override the ref with if the syntax used was
// [refid][]
Text string
}
ReferenceOverrideFunc is expected to be called with a reference string and return either a valid Reference type that the reference string maps to or nil. If overridden is false, the default reference logic will be executed. See the documentation in Options for more details on use-case.
type ReferenceOverrideFunc func(reference string) (ref *Reference, overridden bool)
Renderer is the rendering interface. This is mostly of interest if you are implementing a new rendering format.
Only an HTML implementation is provided in this repository, see the README for external implementations.
type Renderer interface {
// RenderNode is the main rendering method. It will be called once for
// every leaf node and twice for every non-leaf node (first with
// entering=true, then with entering=false). The method should write its
// rendition of the node to the supplied writer w.
RenderNode(w io.Writer, node *Node, entering bool) WalkStatus
// RenderHeader is a method that allows the renderer to produce some
// content preceding the main body of the output document. The header is
// understood in the broad sense here. For example, the default HTML
// renderer will write not only the HTML document preamble, but also the
// table of contents if it was requested.
//
// The method will be passed an entire document tree, in case a particular
// implementation needs to inspect it to produce output.
//
// The output should be written to the supplied writer w. If your
// implementation has no header to write, supply an empty implementation.
RenderHeader(w io.Writer, ast *Node)
// RenderFooter is a symmetric counterpart of RenderHeader.
RenderFooter(w io.Writer, ast *Node)
}
SPRenderer is a struct containing state of a Smartypants renderer.
type SPRenderer struct {
// contains filtered or unexported fields
}
func NewSmartypantsRenderer(flags HTMLFlags) *SPRenderer
NewSmartypantsRenderer constructs a Smartypants renderer object.
func (r *SPRenderer) Process(w io.Writer, text []byte)
Process is the entry point of the Smartypants renderer.
TableCellData contains fields relevant to a TableCell node type.
type TableCellData struct {
IsHeader bool // This tells if it's under the header row
Align CellAlignFlags // This holds the value for align attribute
}
WalkStatus allows NodeVisitor to have some control over the tree traversal. It is returned from NodeVisitor and different values allow Node.Walk to decide which node to go to next.
type WalkStatus int
const (
// GoToNext is the default traversal of every node.
GoToNext WalkStatus = iota
// SkipChildren tells walker to skip all children of current node.
SkipChildren
// Terminate tells walker to terminate the traversal.
Terminate
)