Optional allow only one $ around the latex

markwon-ext-latex/src/main/java/io/noties/markwon/ext/latex/JLatexMathInlineProcessor.java

@@ -1,19 +1,36 @@
 package io.noties.markwon.ext.latex;
 
-import androidx.annotation.Nullable;
-
 import org.commonmark.node.Node;
 
 import java.util.regex.Pattern;
 
+import androidx.annotation.Nullable;
+import androidx.annotation.VisibleForTesting;
 import io.noties.markwon.inlineparser.InlineProcessor;
 
 /**
  * @since 4.3.0
  */
 class JLatexMathInlineProcessor extends InlineProcessor {
 
-    private static final Pattern RE = Pattern.compile("(\\${2})([\\s\\S]+?)\\1");
+    private static final Pattern singleOrDoubleDollar =
+        Pattern.compile("(\\${2})([\\s\\S]+?)(\\${2})|(\\$)([\\s\\S]+?)(\\$)");
+    private static final Pattern doubleDollar =
+        Pattern.compile("(\\${2})([\\s\\S]+?)\\1");
+
+    private final boolean allowSingle$;
+
+    @VisibleForTesting
+    final Pattern pattern;
+
+    JLatexMathInlineProcessor() {
+        this(false);
+    }
+
+    JLatexMathInlineProcessor(boolean allowSingle$) {
+        this.allowSingle$ = allowSingle$;
+        this.pattern = allowSingle$ ? singleOrDoubleDollar : doubleDollar;
+    }
 
     @Override
     public char specialCharacter() {
@@ -24,13 +41,25 @@ public char specialCharacter() {
     @Override
     protected Node parse() {
 
-        final String latex = match(RE);
+        final String latex = match(pattern);
         if (latex == null) {
             return null;
         }
 
         final JLatexMathNode node = new JLatexMathNode();
-        node.latex(latex.substring(2, latex.length() - 2));
+        node.latex(trimDollar(latex));
         return node;
     }
+
+    @SuppressWarnings("DuplicateExpressions")
+    @VisibleForTesting
+    String trimDollar(String latex) {
+        if (allowSingle$) {
+            return latex.startsWith("$$") && latex.endsWith("$$")
+                ? latex.substring(2, latex.length() - 2)
+                : latex.substring(1, latex.length() - 1);
+        } else {
+            return latex.substring(2, latex.length() - 2);
+        }
+    }
 }

markwon-ext-latex/src/main/java/io/noties/markwon/ext/latex/JLatexMathPlugin.java

@@ -119,6 +119,7 @@ static class Config {
         final boolean blocksEnabled;
         final boolean blocksLegacy;
         final boolean inlinesEnabled;
+        final boolean allowInlineSingle$;
 
         // @since 4.3.0
         final ErrorHandler errorHandler;
@@ -130,6 +131,7 @@ static class Config {
             this.blocksEnabled = builder.blocksEnabled;
             this.blocksLegacy = builder.blocksLegacy;
             this.inlinesEnabled = builder.inlinesEnabled;
+            this.allowInlineSingle$ = builder.allowInlineSingle$;
             this.errorHandler = builder.errorHandler;
             // @since 4.0.0
             ExecutorService executorService = builder.executorService;
@@ -160,7 +162,7 @@ public void configure(@NonNull Registry registry) {
         if (config.inlinesEnabled) {
             registry.require(MarkwonInlineParserPlugin.class)
                     .factoryBuilder()
-                    .addInlineProcessor(new JLatexMathInlineProcessor());
+                    .addInlineProcessor(new JLatexMathInlineProcessor(config.allowInlineSingle$));
         }
     }
 
@@ -285,6 +287,7 @@ public static class Builder {
         private boolean blocksEnabled = true;
         private boolean blocksLegacy;
         private boolean inlinesEnabled;
+        private boolean allowInlineSingle$;
 
         // @since 4.3.0
         private ErrorHandler errorHandler;
@@ -331,6 +334,16 @@ public Builder inlinesEnabled(boolean inlinesEnabled) {
             return this;
         }
 
+        /**
+         * @param inlineSingleDollar indicates if $xxx$ is valid.
+         * @since 4.7.0
+         */
+        @NonNull
+        public Builder allowInlinesSingleDollar(boolean inlineSingleDollar){
+            this.allowInlineSingle$ = inlineSingleDollar;
+            return this;
+        }
+
         @NonNull
         public Builder errorHandler(@Nullable ErrorHandler errorHandler) {
             this.errorHandler = errorHandler;

markwon-ext-latex/src/test/java/io/noties/markwon/ext/latex/JLatexMathInlineParserTest.java

@@ -0,0 +1,98 @@
+package io.noties.markwon.ext.latex;
+
+import org.junit.Assert;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+import java.util.regex.Matcher;
+
+/**
+ * @author YvesCheung
+ * 2023/6/14
+ */
+@RunWith(Parameterized.class)
+public class JLatexMathInlineParserTest {
+
+    @Parameterized.Parameters
+    public static Object[][] data() {
+        return new Object[][]{
+            {true, "$ a $", "$ a $", " a "},
+            {false, "$ a $", "", ""},
+
+            {true, "ashdksa $ a $sfalhs", "$ a $", " a "},
+            {false, "ashdksa $ a $sfalhs", "", ""},
+
+            {true, "c sajdl asjkdhk $abc$\n sahdila", "$abc$", "abc"},
+            {false, "c sajdl asjkdhk $abc$\n sahdila", "", ""},
+
+            {true, "c sajdl asjkdhk \n$abcd $ sahdila", "$abcd $", "abcd "},
+            {false, "c sajdl asjkdhk \n$abcd $ sahdila", "", ""},
+
+            {true, "$$abc$$", "$$abc$$", "abc"},
+            {false, "$$abc$$", "$$abc$$", "abc"},
+
+            {true, "$$abc$", "$$abc$", "$abc"},
+            {false, "$$abc$", "", ""},
+
+            {true, "lllll bbb xxx $dhaksdhk\n asd ${b}", "$dhaksdhk\n asd $", "dhaksdhk\n asd "},
+            {false, "lllll bbb xxx $dhaksdhk\n asd ${b}", "", ""},
+
+            {true, "aaa yyy $$bb $ dddd$", "$$bb $", "$bb "},
+            {false, "aaa yyy $$bb $ dddd$", "", ""},
+
+            {true, "aaa $sagdkg$$ Hello", "$sagdkg$", "sagdkg"},
+            {false, "aaa $sagdkg$$ Hello", "", ""},
+
+            {true, "lllll bbb xxx dhaksdhk\n asd ${b}", "", ""},
+            {false, "lllll bbb xxx dhaksdhk\n asd ${b}", "", ""},
+
+            {true, "asdhfalkhasl suaflhslia lasdjikaih sahk", "", ""},
+            {false, "asdhfalkhasl suaflhslia lasdjikaih sahk", "", ""},
+
+            {true, "lllll bbb $xxx dhaksdhk\n asd", "", ""},
+            {false, "lllll bbb $xxx dhaksdhk\n asd", "", ""}
+        };
+    }
+
+    @Parameterized.Parameter(0)
+    public boolean allowSingle$;
+
+    @Parameterized.Parameter(1)
+    public String input;
+
+    @Parameterized.Parameter(2)
+    public String output;
+
+    @Parameterized.Parameter(3)
+    public String trimOutput;
+
+    @Test
+    public void match() {
+        JLatexMathInlineProcessor processor = new JLatexMathInlineProcessor(allowSingle$);
+        Matcher matcher = processor.pattern.matcher(input);
+        if (output == null || "".equals(output)) {
+            Assert.assertFalse(matcher.find());
+        } else {
+            Assert.assertTrue(matcher.find());
+            String actual = matcher.group();
+            Assert.assertEquals(output, actual);
+            Assert.assertEquals(trimOutput, processor.trimDollar(actual));
+        }
+    }
+
+    @Test
+    public void not_match() {
+        String[][] testCase = new String[][]{
+            new String[]{"lllll bbb xxx dhaksdhk\n asd ${b}"},
+            new String[]{"asdhfalkhasl suaflhslia lasdjikaih sahk"},
+            new String[]{"lllll bbb $xxx dhaksdhk\n asd"},
+        };
+        for (String[] c : testCase) {
+            String input = c[0];
+            JLatexMathInlineProcessor processor = new JLatexMathInlineProcessor(true);
+            Matcher matcher = processor.pattern.matcher(input);
+            Assert.assertFalse(matcher.find());
+        }
+    }
+}