Fix multiline see tags in XML documentation (#3435)

Fix `HumanizeHrefTags` not working when see tag spans over multiple lines.

Author: Focus1337

src/Swashbuckle.AspNetCore.SwaggerGen/XmlComments/XmlCommentsTextHelper.cs

@@ -219,7 +219,7 @@ internal static string EndOfLine(string xmlCommentEndOfLine)
     private const string CodeTagPattern = @"<c>(?<display>.+?)</c>";
     private const string MultilineCodeTagPattern = @"<code>(?<display>.+?)</code>";
     private const string ParaTagPattern = @"<para>(?<display>.+?)</para>";
-    private const string HrefPattern = @"<see href=\""(.*)\"">(.*)<\/see>";
+    private const string HrefPattern = @"<see\s+href=\""([^""]*)\"">\s*(.*?)\s*<\/see>";
     private const string BrPattern = @"(<br ?\/?>)"; // handles <br>, <br/>, <br />
     private const string LineBreaksPattern = @"\r?\n";
     private const string DoubleUpLineBreaksPattern = @"(\r?\n){2,}";
@@ -237,7 +237,7 @@ internal static string EndOfLine(string xmlCommentEndOfLine)
     [GeneratedRegex(ParaTagPattern, RegexOptions.Singleline)]
     private static partial Regex ParaTag();
 
-    [GeneratedRegex(HrefPattern)]
+    [GeneratedRegex(HrefPattern, RegexOptions.Singleline)]
     private static partial Regex HrefTag();
 
     [GeneratedRegex(BrPattern)]

test/Swashbuckle.AspNetCore.SwaggerGen.Test/XmlComments/XmlCommentsTextHelperTests.cs

@@ -142,6 +142,19 @@ public void Humanize_HumanizesInlineTags(
         Assert.Equal(expectedOutput, output, false, true);
     }
 
+    [Fact]
+    public void Humanize_SeeMultiLineTag()
+    {
+        const string input = @"
+            <see href=""https://www.iso.org/iso-4217-currency-codes.html"">
+            ISO currency code
+            </see>";
+
+        var output = XmlCommentsTextHelper.Humanize(input);
+
+        Assert.Equal("[ISO currency code](https://www.iso.org/iso-4217-currency-codes.html)", output, false, true);
+    }
+
     [Theory]
     [InlineData("\r\n")]
     [InlineData("\n")]