fix(ui): document viewer back button returns to the page you came from (chat or sources)

tests/unit/test_document_viewer.py

@@ -160,18 +160,26 @@ def test_content_requires_both_params() -> None:
 
 def test_viewer_url_builder_present_in_chat_and_sources() -> None:
     """Both entry points (chat chips, Sources rows) build the same
-    encoded viewer URL and open it in a new tab with rel=noopener."""
+    encoded viewer URL and open it in a new tab with rel=noopener.
+
+    Phase 13: the chat builder additionally carries ``back=/`` (encoded
+    %2F) so the viewer's back button returns to the chat; Sources links
+    intentionally omit the param (the viewer's /sources.html default)."""
     for name, js in (("app.js", _read(APP_JS)), ("sources.js", _read(SOURCES_JS))):
-        assert "function documentUrl(source, path)" in js, name
         assert '"/document.html?source=" + encodeURIComponent(' in js, name
         assert '"&path=" + encodeURIComponent(' in js, name
 
     app_js = _read(APP_JS)
-    assert "chip.href = documentUrl(s.source, s.path)" in app_js
+    # Chat: 3-arg builder with back defaulting to the chat page.
+    assert 'function documentUrl(source, path, back = "/")' in app_js
+    assert '"&back=" + encodeURIComponent(back)' in app_js
+    assert 'chip.href = documentUrl(s.source, s.path, "/")' in app_js
     assert 'chip.target = "_blank"' in app_js
     assert 'chip.rel = "noopener"' in app_js
 
     sources_js = _read(SOURCES_JS)
+    # Sources: unchanged 2-arg builder — no back param in the URL.
+    assert "function documentUrl(source, path)" in sources_js
     assert 'link.className = "doc-link"' in sources_js
     assert "link.href = documentUrl(d.source, d.path)" in sources_js
     assert 'link.target = "_blank"' in sources_js
@@ -188,7 +196,9 @@ def _run_node(script: str) -> str:
 
 
 def _extract_function(js: str, name: str) -> str:
-    match = re.search(rf"(?:export )?function {name}\(source, path\) \{{.*?\n\}}", js, re.S)
+    match = re.search(
+        rf"(?:export )?function {name}\(source, path(?:, back = \"/\")?\) \{{.*?\n\}}", js, re.S
+    )
     assert match, f"{name}(source, path) not found"
     return match.group(0).replace("export ", "", 1)
 
@@ -196,18 +206,21 @@ def _extract_function(js: str, name: str) -> str:
 @pytest.mark.skipif(not HAVE_NODE, reason="node not available")
 def test_viewer_url_builder_encodes_spaces_and_slashes() -> None:
     """Behavioral check of the real builder (app.js) under node: slashes
-    and spaces in source/path values must come out percent-encoded."""
+    and spaces in source/path values must come out percent-encoded, and
+    the back target is appended + encoded (phase 13)."""
     fn = _extract_function(_read(APP_JS), "documentUrl")
     out = _run_node(
         f"{fn}\n"
         "console.log(documentUrl('Homelab', 'kubernetes.md'));\n"
         "console.log(documentUrl('Homelab', 'notes/my file.yaml'));\n"
-        "console.log(documentUrl('H omelab', 'a/b.md'));"
+        "console.log(documentUrl('H omelab', 'a/b.md'));\n"
+        "console.log(documentUrl('Homelab', 'kubernetes.md', '/sources.html'));"
     )
     assert out.splitlines() == [
-        "/document.html?source=Homelab&path=kubernetes.md",
-        "/document.html?source=Homelab&path=notes%2Fmy%20file.yaml",
-        "/document.html?source=H%20omelab&path=a%2Fb.md",
+        "/document.html?source=Homelab&path=kubernetes.md&back=%2F",
+        "/document.html?source=Homelab&path=notes%2Fmy%20file.yaml&back=%2F",
+        "/document.html?source=H%20omelab&path=a%2Fb.md&back=%2F",
+        "/document.html?source=Homelab&path=kubernetes.md&back=%2Fsources.html",
     ]
 
 
@@ -259,10 +272,19 @@ def test_markdown_renderer_stays_xss_safe_and_unchanged() -> None:
 def test_viewer_js_rendering_contracts() -> None:
     """document.js: raw formats go in via textContent (never parsed as
     HTML), markdown via the shared renderer, 404 → designed not-found
-    state, back link prefers browser history when there is one."""
+    state, and (phase 13) the back link resolves the ``back`` param —
+    same-origin relative URLs only, /sources.html default, no browser
+    history heuristics (both entry points are fresh tabs)."""
     js = _read(DOCUMENT_JS)
     assert "pre.textContent = doc.content" in js  # raw formats: text node
     assert "renderMarkdown(doc.content)" in js  # md/markdown: shared renderer
     assert "showNotFound" in js
-    assert "history.length > 1" in js
+    # Phase 13: deterministic back-target resolution, no history heuristics.
+    assert "history.length" not in js
+    assert "window.history.back" not in js
+    assert 'backParam.startsWith("/")' in js  # same-origin relative only…
+    assert 'backParam.startsWith("//")' in js  # …and not protocol-relative
+    assert 'backLink.href = backTarget' in js  # deterministic anchor navigation
+    assert '"/sources.html"' in js  # default target + no-JS fallback value
+    assert '"Chat"' in js and '"Sources"' in js  # labels for the two entry points
     assert "encodeURIComponent" in js  # content fetch uses the same encoding