SPICE-0028: Add support for multi-line string line continuations (#1507)

SPICE: https://github.com/apple/pkl-evolution/pull/31

pkl-core/src/main/java/org/pkl/core/util/SyntaxHighlighter.java

@@ -18,6 +18,7 @@ package org.pkl.core.util;
 import static org.pkl.parser.Token.FALSE;
 import static org.pkl.parser.Token.NULL;
 import static org.pkl.parser.Token.STRING_ESCAPE_BACKSLASH;
+import static org.pkl.parser.Token.STRING_ESCAPE_CONTINUATION;
 import static org.pkl.parser.Token.STRING_ESCAPE_NEWLINE;
 import static org.pkl.parser.Token.STRING_ESCAPE_QUOTE;
 import static org.pkl.parser.Token.STRING_ESCAPE_RETURN;
@@ -41,7 +42,8 @@ public final class SyntaxHighlighter {
           STRING_ESCAPE_RETURN,
           STRING_ESCAPE_QUOTE,
           STRING_ESCAPE_BACKSLASH,
-          STRING_ESCAPE_UNICODE);
+          STRING_ESCAPE_UNICODE,
+          STRING_ESCAPE_CONTINUATION);
 
   private static final EnumSet<Token> constant = EnumSet.of(TRUE, FALSE, NULL);
 

pkl-core/src/test/files/LanguageSnippetTests/input/basic/stringMultilineContinuation.pkl

@@ -0,0 +1,21 @@
+amends "../snippetTest.pkl"
+
+examples {
+  ["string continuation"] {
+    """
+    hello \
+    world
+    """
+
+    #"""
+    hello \#
+    world
+    """#
+  
+    """
+    hello \
+    \
+    world
+    """
+  }
+}

pkl-core/src/test/files/LanguageSnippetTests/input/errors/invalidCharacterEscape2.pkl

@@ -0,0 +1 @@
+res1 = "xxx\ xxx"

pkl-core/src/test/files/LanguageSnippetTests/input/errors/parser19.pkl

@@ -0,0 +1,5 @@
+foo = """
+  hello \
+\
+  world
+  """

pkl-core/src/test/files/LanguageSnippetTests/input/errors/parser20.pkl

@@ -0,0 +1,2 @@
+foo = "hello \
+world"

pkl-core/src/test/files/LanguageSnippetTests/input/errors/parser21.pkl

@@ -0,0 +1,5 @@
+foo =
+  """
+  hello \   
+  world
+  """

pkl-core/src/test/files/LanguageSnippetTests/output/basic/stringMultilineContinuation.pcf

@@ -0,0 +1,7 @@
+examples {
+  ["string continuation"] {
+    "hello world"
+    "hello world"
+    "hello world"
+  }
+}

pkl-core/src/test/files/LanguageSnippetTests/output/errors/invalidCharacterEscape.err

@@ -1,7 +1,7 @@
 –– Pkl Error ––
 Invalid character escape sequence `\a`.
 
-Valid character escape sequences are:  \n  \r  \t  \"  \\
+Valid character escape sequences are:  \n  \r  \t  \"  \\ \<newline>
 
 x | res1 = "xxx\axxx"
                ^^

pkl-core/src/test/files/LanguageSnippetTests/output/errors/invalidCharacterEscape2.err

@@ -0,0 +1,8 @@
+–– Pkl Error ––
+Invalid character escape sequence `\ `.
+
+Valid character escape sequences are:  \n  \r  \t  \"  \\ \<newline>
+
+x | res1 = "xxx\ xxx"
+               ^^
+at invalidCharacterEscape2 (file:///$snippetsDir/input/errors/invalidCharacterEscape2.pkl)

pkl-core/src/test/files/LanguageSnippetTests/output/errors/parser19.err

@@ -0,0 +1,6 @@
+–– Pkl Error ––
+Line must match or exceed indentation of the String's last line.
+
+x | \
+    ^
+at parser19 (file:///$snippetsDir/input/errors/parser19.pkl)

pkl-core/src/test/files/LanguageSnippetTests/output/errors/parser20.err

@@ -0,0 +1,8 @@
+–– Pkl Error ––
+Invalid line continuation escape sequence.
+
+Line continuations are only allowed in multi-line strings.
+
+x | foo = "hello \
+                 ^^
+at parser20 (file:///$snippetsDir/input/errors/parser20.pkl)

pkl-core/src/test/files/LanguageSnippetTests/output/errors/parser21.err

@@ -0,0 +1,8 @@
+–– Pkl Error ––
+Invalid line continuation escape sequence.
+
+Whitespace between the continuation escape and following newline is not allowed.
+
+x | hello \
+          ^^^^^
+at parser21 (file:///$snippetsDir/input/errors/parser21.pkl)