Fix single-quoted environment values retaining their quotes

src/main/java/io/github/cdimascio/dotenv/internal/DotenvParser.java

@@ -36,7 +36,9 @@ public class DotenvParser {
 
     private static final Predicate<String> isWhiteSpace = s -> matches(WHITE_SPACE_REGEX, s);
     private static final Predicate<String> isComment = s -> s.startsWith("#") || s.startsWith("////");
-    private static final Predicate<String> isQuoted = s -> s.length() > 1 && s.startsWith("\"") && s.endsWith("\"");
+    private static final Predicate<String> isQuoted = s -> s.length() > 1
+        && ((s.startsWith("\"") && s.endsWith("\""))
+            || (s.startsWith("'") && s.endsWith("'")));
     private final Function<String, DotenvEntry> parseLine = s -> matchEntry(DOTENV_ENTRY_REGEX, s);
 
     /**
@@ -175,4 +177,3 @@ private static String stripQuotes(String input) {
         }
     }
 }
-

src/test/java/tests/QuotedValuesTests.java

@@ -0,0 +1,52 @@
+package tests;
+
+import io.github.cdimascio.dotenv.Dotenv;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class QuotedValuesTests {
+    @TempDir
+    Path directory;
+
+    private Dotenv load(String contents) throws IOException {
+        Files.writeString(directory.resolve("test.env"), contents);
+        return Dotenv.configure().directory(directory.toString()).filename("test.env").load();
+    }
+
+    @Test
+    void removesMatchingQuotes() throws IOException {
+        final var dotenv = load("PLAIN=value\nSINGLE='value'\nDOUBLE=\"value\"\nEMPTY=''\n");
+
+        assertEquals("value", dotenv.get("PLAIN"));
+        assertEquals("value", dotenv.get("SINGLE"));
+        assertEquals("value", dotenv.get("DOUBLE"));
+        assertEquals("", dotenv.get("EMPTY"));
+    }
+
+    @Test
+    void preservesSingleQuotedContents() throws IOException {
+        final var dotenv = load("SPACES=  '  café  '  \n"
+            + "HASH='value#part' # trailing comment\n"
+            + "DOUBLE_INSIDE='say \"hello\"'\n"
+            + "BACKSLASH='literal\\nvalue'\n");
+
+        assertEquals("  café  ", dotenv.get("SPACES"));
+        assertEquals("value#part", dotenv.get("HASH"));
+        assertEquals("say \"hello\"", dotenv.get("DOUBLE_INSIDE"));
+        assertEquals("literal\\nvalue", dotenv.get("BACKSLASH"));
+    }
+
+    @Test
+    void preservesUnquotedApostrophes() throws IOException {
+        final var dotenv = load("APOSTROPHE=it's unchanged\nTRAILING=parents'\n");
+
+        assertEquals("it's unchanged", dotenv.get("APOSTROPHE"));
+        assertEquals("parents'", dotenv.get("TRAILING"));
+    }
+}