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Source file src/html/template/context.go

Documentation: html/template

     1  // Copyright 2011 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package template
     6  
     7  import (
     8  	"fmt"
     9  )
    10  
    11  // context describes the state an HTML parser must be in when it reaches the
    12  // portion of HTML produced by evaluating a particular template node.
    13  //
    14  // The zero value of type context is the start context for a template that
    15  // produces an HTML fragment as defined at
    16  // https://www.w3.org/TR/html5/syntax.html#the-end
    17  // where the context element is null.
    18  type context struct {
    19  	state   state
    20  	delim   delim
    21  	urlPart urlPart
    22  	jsCtx   jsCtx
    23  	attr    attr
    24  	element element
    25  	err     *Error
    26  }
    27  
    28  func (c context) String() string {
    29  	return fmt.Sprintf("{%v %v %v %v %v %v %v}", c.state, c.delim, c.urlPart, c.jsCtx, c.attr, c.element, c.err)
    30  }
    31  
    32  // eq reports whether two contexts are equal.
    33  func (c context) eq(d context) bool {
    34  	return c.state == d.state &&
    35  		c.delim == d.delim &&
    36  		c.urlPart == d.urlPart &&
    37  		c.jsCtx == d.jsCtx &&
    38  		c.attr == d.attr &&
    39  		c.element == d.element &&
    40  		c.err == d.err
    41  }
    42  
    43  // mangle produces an identifier that includes a suffix that distinguishes it
    44  // from template names mangled with different contexts.
    45  func (c context) mangle(templateName string) string {
    46  	// The mangled name for the default context is the input templateName.
    47  	if c.state == stateText {
    48  		return templateName
    49  	}
    50  	s := templateName + "$htmltemplate_" + c.state.String()
    51  	if c.delim != 0 {
    52  		s += "_" + c.delim.String()
    53  	}
    54  	if c.urlPart != 0 {
    55  		s += "_" + c.urlPart.String()
    56  	}
    57  	if c.jsCtx != 0 {
    58  		s += "_" + c.jsCtx.String()
    59  	}
    60  	if c.attr != 0 {
    61  		s += "_" + c.attr.String()
    62  	}
    63  	if c.element != 0 {
    64  		s += "_" + c.element.String()
    65  	}
    66  	return s
    67  }
    68  
    69  // state describes a high-level HTML parser state.
    70  //
    71  // It bounds the top of the element stack, and by extension the HTML insertion
    72  // mode, but also contains state that does not correspond to anything in the
    73  // HTML5 parsing algorithm because a single token production in the HTML
    74  // grammar may contain embedded actions in a template. For instance, the quoted
    75  // HTML attribute produced by
    76  //     <div title="Hello {{.World}}">
    77  // is a single token in HTML's grammar but in a template spans several nodes.
    78  type state uint8
    79  
    80  //go:generate stringer -type state
    81  
    82  const (
    83  	// stateText is parsed character data. An HTML parser is in
    84  	// this state when its parse position is outside an HTML tag,
    85  	// directive, comment, and special element body.
    86  	stateText state = iota
    87  	// stateTag occurs before an HTML attribute or the end of a tag.
    88  	stateTag
    89  	// stateAttrName occurs inside an attribute name.
    90  	// It occurs between the ^'s in ` ^name^ = value`.
    91  	stateAttrName
    92  	// stateAfterName occurs after an attr name has ended but before any
    93  	// equals sign. It occurs between the ^'s in ` name^ ^= value`.
    94  	stateAfterName
    95  	// stateBeforeValue occurs after the equals sign but before the value.
    96  	// It occurs between the ^'s in ` name =^ ^value`.
    97  	stateBeforeValue
    98  	// stateHTMLCmt occurs inside an <!-- HTML comment -->.
    99  	stateHTMLCmt
   100  	// stateRCDATA occurs inside an RCDATA element (<textarea> or <title>)
   101  	// as described at https://www.w3.org/TR/html5/syntax.html#elements-0
   102  	stateRCDATA
   103  	// stateAttr occurs inside an HTML attribute whose content is text.
   104  	stateAttr
   105  	// stateURL occurs inside an HTML attribute whose content is a URL.
   106  	stateURL
   107  	// stateSrcset occurs inside an HTML srcset attribute.
   108  	stateSrcset
   109  	// stateJS occurs inside an event handler or script element.
   110  	stateJS
   111  	// stateJSDqStr occurs inside a JavaScript double quoted string.
   112  	stateJSDqStr
   113  	// stateJSSqStr occurs inside a JavaScript single quoted string.
   114  	stateJSSqStr
   115  	// stateJSRegexp occurs inside a JavaScript regexp literal.
   116  	stateJSRegexp
   117  	// stateJSBlockCmt occurs inside a JavaScript /* block comment */.
   118  	stateJSBlockCmt
   119  	// stateJSLineCmt occurs inside a JavaScript // line comment.
   120  	stateJSLineCmt
   121  	// stateCSS occurs inside a <style> element or style attribute.
   122  	stateCSS
   123  	// stateCSSDqStr occurs inside a CSS double quoted string.
   124  	stateCSSDqStr
   125  	// stateCSSSqStr occurs inside a CSS single quoted string.
   126  	stateCSSSqStr
   127  	// stateCSSDqURL occurs inside a CSS double quoted url("...").
   128  	stateCSSDqURL
   129  	// stateCSSSqURL occurs inside a CSS single quoted url('...').
   130  	stateCSSSqURL
   131  	// stateCSSURL occurs inside a CSS unquoted url(...).
   132  	stateCSSURL
   133  	// stateCSSBlockCmt occurs inside a CSS /* block comment */.
   134  	stateCSSBlockCmt
   135  	// stateCSSLineCmt occurs inside a CSS // line comment.
   136  	stateCSSLineCmt
   137  	// stateError is an infectious error state outside any valid
   138  	// HTML/CSS/JS construct.
   139  	stateError
   140  )
   141  
   142  // isComment is true for any state that contains content meant for template
   143  // authors & maintainers, not for end-users or machines.
   144  func isComment(s state) bool {
   145  	switch s {
   146  	case stateHTMLCmt, stateJSBlockCmt, stateJSLineCmt, stateCSSBlockCmt, stateCSSLineCmt:
   147  		return true
   148  	}
   149  	return false
   150  }
   151  
   152  // isInTag return whether s occurs solely inside an HTML tag.
   153  func isInTag(s state) bool {
   154  	switch s {
   155  	case stateTag, stateAttrName, stateAfterName, stateBeforeValue, stateAttr:
   156  		return true
   157  	}
   158  	return false
   159  }
   160  
   161  // delim is the delimiter that will end the current HTML attribute.
   162  type delim uint8
   163  
   164  //go:generate stringer -type delim
   165  
   166  const (
   167  	// delimNone occurs outside any attribute.
   168  	delimNone delim = iota
   169  	// delimDoubleQuote occurs when a double quote (") closes the attribute.
   170  	delimDoubleQuote
   171  	// delimSingleQuote occurs when a single quote (') closes the attribute.
   172  	delimSingleQuote
   173  	// delimSpaceOrTagEnd occurs when a space or right angle bracket (>)
   174  	// closes the attribute.
   175  	delimSpaceOrTagEnd
   176  )
   177  
   178  // urlPart identifies a part in an RFC 3986 hierarchical URL to allow different
   179  // encoding strategies.
   180  type urlPart uint8
   181  
   182  //go:generate stringer -type urlPart
   183  
   184  const (
   185  	// urlPartNone occurs when not in a URL, or possibly at the start:
   186  	// ^ in "^http://auth/path?k=v#frag".
   187  	urlPartNone urlPart = iota
   188  	// urlPartPreQuery occurs in the scheme, authority, or path; between the
   189  	// ^s in "h^ttp://auth/path^?k=v#frag".
   190  	urlPartPreQuery
   191  	// urlPartQueryOrFrag occurs in the query portion between the ^s in
   192  	// "http://auth/path?^k=v#frag^".
   193  	urlPartQueryOrFrag
   194  	// urlPartUnknown occurs due to joining of contexts both before and
   195  	// after the query separator.
   196  	urlPartUnknown
   197  )
   198  
   199  // jsCtx determines whether a '/' starts a regular expression literal or a
   200  // division operator.
   201  type jsCtx uint8
   202  
   203  //go:generate stringer -type jsCtx
   204  
   205  const (
   206  	// jsCtxRegexp occurs where a '/' would start a regexp literal.
   207  	jsCtxRegexp jsCtx = iota
   208  	// jsCtxDivOp occurs where a '/' would start a division operator.
   209  	jsCtxDivOp
   210  	// jsCtxUnknown occurs where a '/' is ambiguous due to context joining.
   211  	jsCtxUnknown
   212  )
   213  
   214  // element identifies the HTML element when inside a start tag or special body.
   215  // Certain HTML element (for example <script> and <style>) have bodies that are
   216  // treated differently from stateText so the element type is necessary to
   217  // transition into the correct context at the end of a tag and to identify the
   218  // end delimiter for the body.
   219  type element uint8
   220  
   221  //go:generate stringer -type element
   222  
   223  const (
   224  	// elementNone occurs outside a special tag or special element body.
   225  	elementNone element = iota
   226  	// elementScript corresponds to the raw text <script> element
   227  	// with JS MIME type or no type attribute.
   228  	elementScript
   229  	// elementStyle corresponds to the raw text <style> element.
   230  	elementStyle
   231  	// elementTextarea corresponds to the RCDATA <textarea> element.
   232  	elementTextarea
   233  	// elementTitle corresponds to the RCDATA <title> element.
   234  	elementTitle
   235  )
   236  
   237  //go:generate stringer -type attr
   238  
   239  // attr identifies the current HTML attribute when inside the attribute,
   240  // that is, starting from stateAttrName until stateTag/stateText (exclusive).
   241  type attr uint8
   242  
   243  const (
   244  	// attrNone corresponds to a normal attribute or no attribute.
   245  	attrNone attr = iota
   246  	// attrScript corresponds to an event handler attribute.
   247  	attrScript
   248  	// attrScriptType corresponds to the type attribute in script HTML element
   249  	attrScriptType
   250  	// attrStyle corresponds to the style attribute whose value is CSS.
   251  	attrStyle
   252  	// attrURL corresponds to an attribute whose value is a URL.
   253  	attrURL
   254  	// attrSrcset corresponds to a srcset attribute.
   255  	attrSrcset
   256  )
   257  

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