unambiguous multiline strings (#414)

Fixes: https://github.com/kdl-org/kdl/issues/413

README.md

@@ -25,11 +25,15 @@ package {
 
   scripts {
     // "Raw" and dedented multi-line strings are supported.
-    build #"
+    message """
+      hello
+      world
+      """
+    build #"""
       echo "foo"
       node -c "console.log('hello, world!');"
       echo "foo" > some-file.txt
-      "#
+      """#
   }
 
   // `\` breaks up a single node across multiple lines.

SPEC.md

@@ -440,14 +440,14 @@ The string contains the literal characters `hello\n\r\asd"#world`
 
 ### Multi-line Strings
 
-When a Quoted or Raw String spans multiple lines with literal, non-escaped
+Quoted and Raw Strings support multiple lines with literal, non-escaped
-Newlines, it follows a special multi-line syntax that automatically "dedents"
+Newlines. They must use a special multi-line syntax, and they automatically
-the string, allowing its value to be indented to a visually matching level if
+"dedent" the string, allowing its value to be indented to a visually matching
-desired.
+level as desired.
 
 A Multi-line string _MUST_ start with a [Newline](#newline) immediately
-following its opening `"`. Its final line _MUST_ contain only whitespace,
+following its opening `"""` (whether Quoted or Raw). Its final line _MUST_ contain only whitespace,
-followed by a single closing `"`. All in-between lines that contain
+followed by a closing `"""`. All in-between lines that contain
 non-newline characters _MUST_ start with _at least_ the exact same whitespace
 as the final line (precisely matching codepoints, not merely counting characters).
 They may contain additional whitespace following this prefix.
@@ -457,13 +457,14 @@ Whitespace of the last line, and the matching Whitespace prefix on all
 intermediate lines. The first and last Newline can be the same character (that
 is, empty multi-line strings are legal).
 
-Strings with literal Newlines that do not immediately start with a Newline and
-whose final `"` is not preceeded by optional whitespace and a Newline are
-illegal.
-
 In other words, the final line specifies the whitespace prefix that will be
 removed from all other lines.
 
+Multi-line Strings that do not immediately start with a Newline and whose final
+`"""` is not preceeded by optional whitespace and a Newline are illegal. This
+also means that `"""` may not be used for a single-line String (e.g.
+`"""foo"""`).
+
 It is a syntax error for any body lines of the multi-line string to not match
 the whitespace prefix of the last line with the final quote.
 
@@ -474,7 +475,20 @@ Literal Newline sequences in Multi-line Strings must be normalized to a single
 becomes a single `LF` during parsing.
 
 This normalization does not apply to non-literal Newlines entered using escape
-sequences.
+sequences. That is:
+
+```kdl
+multi-line """
+    \r\n[CRLF]
+    foo[CRLF]
+    """
+```
+
+becomes:
+
+```kdl
+"\r\n\nfoo"
+```
 
 For clarity: this normalization is for individual sequences. That is, the
 literal sequence `CRLF CRLF` becomes `LF LF`, not `LF`.
@@ -482,11 +496,11 @@ literal sequence `CRLF CRLF` becomes `LF LF`, not `LF`.
 #### Example
 
 ```kdl
-multi-line "
+multi-line """
         foo
     This is the base indentation
             bar
-    "
+    """
 ```
 
 This example's string value will be:
@@ -506,11 +520,11 @@ If the last line wasn't indented as far,
 it won't dedent the rest of the lines as much:
 
 ```kdl
-multi-line "
+multi-line """
         foo
     This is no longer on the left edge
             bar
-  "
+  """
 ```
 
 This example's string value will be:
@@ -528,11 +542,11 @@ Equivalent to `"      foo\n  This is no longer on the left edge\n          bar"`
 Empty lines can contain any whitespace, or none at all, and will be reflected as empty in the value:
 
 ```kdl
-multi-line "
+multi-line """
     Indented a bit
 
     A second indented paragraph.
-    "
+    """
 ```
 
 This example's string value will be:
@@ -547,25 +561,29 @@ Equivalent to `"Indented a bit.\n\nA second indented paragraph."`
 
 -----------
 
-The following yield syntax errors:
+The following yield **syntax errors**:
 
 ```kdl
-multi-line "
+multi-line """can't be single line"""
-  closing quote with non-whitespace prefix"
 ```
 
 ```kdl
-multi-line "stuff
+multi-line """
-  "
+  closing quote with non-whitespace prefix"""
+```
+
+```kdl
+multi-line """stuff
+  """
 ```
 
 ```kdl
 // Every line must share the exact same prefix as the closing line.
-multi-line "[\n]
+multi-line """[\n]
 [tab]a[\n]
 [space][space]b[\n]
 [space][tab][\n]
-[tab]"
+[tab]"""
 ```
 
 #### Interaction with Whitespace Escapes
@@ -581,24 +599,25 @@ For example, the following example is illegal:
 
 ```kdl
   // Equivalent to trying to write a string containing `foo\nbar\`.
-  "
+  """
   foo
   bar\
-  "
+  """
 ```
 
 while the following example is allowed
 ```kdl
-  "
+  """
   foo \
 bar
   baz
-  \   "
+  \   """
-  // this is equivalent to
+  
-  "
+  // equivalent to
+  """
   foo bar
   baz
-  "
+  """
 ```
 
 ### Number
@@ -800,7 +819,7 @@ dotted-ident := sign? '.' ((identifier-char - digit) identifier-char*)?
 identifier-char := unicode - unicode-space - newline - [\\/(){};\[\]"#=] - disallowed-literal-code-points - equals-sign
 disallowed-keyword-identifiers := 'true' - 'false' - 'null' - 'inf' - '-inf' - 'nan'
 
-quoted-string := '"' (single-line-string-body | newline multi-line-string-body newline unicode-space*) '"'
+quoted-string := '"' single-line-string-body '"' | '"""' newline multi-line-string-body newline unicode-space*) '"""'
 single-line-string-body := (string-character - newline)*
 multi-line-string-body := string-character*
 string-character := '\' escape | [^\\"] - disallowed-literal-code-points
@@ -808,7 +827,7 @@ escape := ["\\bfnrts] | 'u{' hex-digit{1, 6} '}' | (unicode-space | newline)+
 hex-digit := [0-9a-fA-F]
 
 raw-string := '#' raw-string-quotes '#' | '#' raw-string '#'
-raw-string-quotes := '"' (single-line-raw-string-body | newline multi-line-raw-string-body newline unicode-space*) '"'
+raw-string-quotes := '"' single-line-raw-string-body '"' | '"""' newline multi-line-raw-string-body newline unicode-space*) '"""'
 single-line-raw-string-body := (unicode - newline - disallowed-literal-code-points)*
 multi-line-raw-string-body := (unicode - disallowed-literal-code-points)*
 

examples/ci.kdl

@@ -42,11 +42,11 @@ jobs {
       }
       step Clippy { run cargo clippy --all -- -D warnings }
       step "Run tests" { run cargo test --all --verbose }
-      step "Other Stuff" run="
+      step "Other Stuff" run="""
         echo foo
         echo bar
         echo baz
-        "
+        """
     }
   }
 }

tests/test_cases/input/multiline_raw_string_indented.kdl

@@ -1,5 +1,5 @@
-node #"
+node #"""
     hey
    everyone
      how goes?
-  "#
+  """#

tests/test_cases/input/multiline_raw_string_non_matching_prefix_character_error.kdl

@@ -1,5 +1,5 @@
-node #"
+node #"""
     hey
    everyone
 	   how goes?
-  "#
+  """#

tests/test_cases/input/multiline_raw_string_non_matching_prefix_count_error.kdl

@@ -1,5 +1,5 @@
-node #"
+node #"""
     hey
  everyone
      how goes?
-  "#
+  """#

tests/test_cases/input/multiline_raw_string_single_line_err.kdl

@@ -0,0 +1 @@
+node #"""one line"""#

tests/test_cases/input/multiline_raw_string_single_quote_err.kdl

@@ -0,0 +1,5 @@
+node #"""
+hey
+everyone
+how goes?
+"""#

tests/test_cases/input/multiline_string.kdl

@@ -1,5 +1,5 @@
-node "
+node """
 hey
 everyone
 how goes?
-"
+"""

tests/test_cases/input/multiline_string_indented.kdl

@@ -1,5 +1,5 @@
-node "
+node """
     hey
    everyone
      how goes?
-  "
+  """

tests/test_cases/input/multiline_string_non_matching_prefix_character_error.kdl

@@ -1,5 +1,5 @@
-node "
+node """
     hey
    everyone
 	   how goes?
-  "
+  """

tests/test_cases/input/multiline_string_non_matching_prefix_count_error.kdl

@@ -1,5 +1,5 @@
-node "
+node """
     hey
  everyone
      how goes?
-  "
+  """

tests/test_cases/input/multiline_string_single_line_err.kdl

@@ -0,0 +1 @@
+node """one line"""

tests/test_cases/input/multiline_string_single_quote_err.kdl

@@ -0,0 +1,5 @@
+node "
+hey
+everyone
+how goes?
+"