Fixed local source links being refused by Word and LibreOffice

app/Tests/Tools/FileExportFormatTests.cs

@@ -0,0 +1,39 @@
+using AIStudio.Tools;
+
+namespace AIStudio.Tests.Tools;
+
+/// <summary>
+/// Checks what AI Studio assumes about the readers of the formats it writes.
+/// </summary>
+[TestFixture]
+public sealed class FileExportFormatTests
+{
+    [Test]
+    public void OnlyTheTwoOfficeFormatsRefuseAPageInALocalLink()
+    {
+        Assert.Multiple(() =>
+        {
+            Assert.That(FileExportFormat.MICROSOFT_WORD.FollowsPageAnchors(), Is.False, "Word looks for a file whose name ends in the fragment, finds none, and refuses the link.");
+            Assert.That(FileExportFormat.OPEN_DOCUMENT_TEXT.FollowsPageAnchors(), Is.False, "LibreOffice does the same, verified on 2026-09-15 with an exported .odt.");
+            Assert.That(FileExportFormat.HTML.FollowsPageAnchors(), Is.True, "A browser opens the document on the page the fragment names.");
+            Assert.That(FileExportFormat.MARKDOWN.FollowsPageAnchors(), Is.True);
+            Assert.That(FileExportFormat.LATEX.FollowsPageAnchors(), Is.True);
+        });
+    }
+
+    [Test]
+    public void EveryFormatAnAnswerIsWrittenAsHasAnAnswerHere()
+    {
+        // Whoever adds a format decides what its reader can follow, rather than inheriting an
+        // assumption. This fails for a format which nobody thought about, because the list below
+        // has to name it:
+        Assert.That(FileExportFormatExtensions.ANSWER_FORMATS, Is.EquivalentTo(new[]
+        {
+            FileExportFormat.MICROSOFT_WORD,
+            FileExportFormat.OPEN_DOCUMENT_TEXT,
+            FileExportFormat.LATEX,
+            FileExportFormat.MARKDOWN,
+            FileExportFormat.HTML,
+        }), "A format was added to or removed from the export menu: say in FollowsPageAnchors whether its reader follows a page in a local link, then name it here.");
+    }
+}

app/Tests/Tools/SourceExtensionsTests.cs

@@ -137,6 +137,36 @@ public sealed class SourceExtensionsTests
             Assert.That(entries[index], Does.StartWith($"- [{listed[index].Number}] ").And.Contains(listed[index].Source.Title), "The Markdown and the chat read the same grouping, so a source cannot be numbered one way here and another way there.");
     }
 
+    [Test]
+    public void AReaderWhichCannotFollowAPageGetsTheDocumentWithoutOne()
+    {
+        IList<Source> sources =
+        [
+            new("Handbook (Page 266)", "file:///Users/someone/My Documents/handbook.pdf#page=266", SourceOrigin.RAG),
+            new("An older answer", "file:///Users/someone/handbook.pdf#chunk=3", SourceOrigin.RAG),
+            new("A section of an article", "https://example.org/article#results", SourceOrigin.LLM),
+        ];
+
+        Assert.That(EntriesOf(sources.ToMarkdown(keepPageAnchors: false)), Is.EqualTo(new[]
+        {
+            "- [1] [A section of an article](<https://example.org/article#results>)",
+            "- [2] [Handbook (Page 266)](<file:///Users/someone/My%20Documents/handbook.pdf>)",
+            "- [3] [An older answer](<file:///Users/someone/handbook.pdf>)",
+        }), "Word and LibreOffice take the fragment of a local link for part of the file name and refuse the link, so the local links lose it -- and the web link keeps its own, where a fragment names a section of the page and belongs to the address.");
+    }
+
+    [Test]
+    public void AReaderWhichFollowsAPageIsToldIt()
+    {
+        IList<Source> sources = [new("Handbook (Page 266)", "file:///Users/someone/handbook.pdf#page=266", SourceOrigin.RAG)];
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(EntriesOf(sources.ToMarkdown()).Single(), Does.EndWith("handbook.pdf#page=266>)"), "A browser and a PDF reader open the document where the passage is, so they are told the page.");
+            Assert.That(EntriesOf(sources.ToExportMarkdown()).Single(), Does.EndWith("handbook.pdf#page=266>)"), "The clipboard and every text format keep it as well; only the two office formats ask for it to be dropped.");
+        });
+    }
+
     [Test]
     public void AKnownPageRidesInTheLinkOfASource()
     {