fix: clear stale empty-state and grid content on new search

static/script.js

@@ -640,10 +640,12 @@ updateProfileWidgets();
     btnLabel.style.display = isLoading ? "none" : "inline";
     btnLoading.style.display = isLoading ? "inline-flex" : "none";
     if (isLoading) {
-      resultsSection.style.display = "block";
-      resultsLoadingEl.style.display = "block";
+      resultsGrid.innerHTML = "";         
       resultsGrid.style.display = "none";
       resultsEmptyEl.style.display = "none";
+      resultsEmptyEl.textContent = "";
+      resultsLoadingEl.style.display = "block";
+      resultsSection.style.display = "block";
       resultsSection.scrollIntoView({ behavior: "smooth" });
     } else {
       resultsLoadingEl.style.display = "none";
@@ -809,15 +811,19 @@ updateProfileWidgets();
   function renderResults(projects, message) {
     resultsSection.style.display = "block";
     resultsLoadingEl.style.display = "none";
-    resultsGrid.textContent = "";
+    // Always wipe the grid and hide both states before deciding what to show
+    resultsGrid.innerHTML = "";
+    resultsGrid.style.display = "none";
+    resultsEmptyEl.style.display = "none";
+    if (emptyMessageEl) { emptyMessageEl.textContent = ""; }
     if (!projects || projects.length === 0) {
-      resultsGrid.style.display = "none";
       resultsEmptyEl.style.display = "block";
-      emptyMessageEl.textContent = message || "Try adjusting your skills or choosing a different interest area.";
+      if (emptyMessageEl) {
+        emptyMessageEl.textContent = message || "Try adjusting your skills or choosing a different interest area.";
+      }
       resultsSection.scrollIntoView({ behavior: "smooth" });
       return;
     }
-    resultsEmptyEl.style.display = "none";
     resultsGrid.style.display = "grid";
     projects.forEach(function (project) { resultsGrid.appendChild(buildProjectCard(project)); });
     resultsSection.scrollIntoView({ behavior: "smooth" });

tests/test_no_results_reset.py

@@ -0,0 +1,245 @@
+# tests/test_no_results_reset.py
+# Tests for bug #730 — "No Projects Found" state must fully clear when
+# the user submits a new search after a zero-result query.
+#
+# What is tested
+# --------------
+# 1. The API correctly returns an empty project list for no-match inputs.
+# 2. The API correctly returns projects for match inputs.
+# 3. Successive API calls behave independently — a prior empty result does
+#    not pollute the next successful result (state lives only in the
+#    response, not the server).
+# 4. The empty-state message field is present in API responses that have
+#    no matches, so the JS can populate emptyMessageEl safely.
+# 5. The results section HTML landmark and its three sub-states
+#    (loading, empty, grid) all exist in the page so the JS selectors
+#    in setLoadingState / renderResults are guaranteed to resolve.
+# 6. script.js is served and contains both fixed functions.
+#
+# Run with:  python -m pytest tests/test_no_results_reset.py -v
+
+import sys
+import os
+
+import pytest
+
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), ".."))
+
+from app import app
+
+
+# ---------------------------------------------------------------------------
+# Fixture
+# ---------------------------------------------------------------------------
+
+@pytest.fixture
+def client():
+    app.config["TESTING"] = True
+    with app.test_client() as c:
+        yield c
+
+
+# ---------------------------------------------------------------------------
+# Helper payloads
+# ---------------------------------------------------------------------------
+
+NO_MATCH_PAYLOAD = {
+    "skills": "Python",
+    "level": "Advanced",
+    "interest": "Machine Learning/AI",
+    "time": "Low"
+}
+
+MATCH_PAYLOAD = {
+    "skills": "Python",
+    "level": "Beginner",
+    "interest": "Data",
+    "time": "Low"
+}
+
+
+# ---------------------------------------------------------------------------
+# API state independence — the core of the bug
+# ---------------------------------------------------------------------------
+
+def test_no_match_returns_empty_list(client):
+    """A blocked interest must return an empty projects list."""
+    response = client.post("/api/recommend", json=NO_MATCH_PAYLOAD)
+    assert response.status_code == 200
+    data = response.get_json()
+    assert data["projects"] == []
+
+
+def test_no_match_returns_message_field(client):
+    """Empty result must include a 'message' key for emptyMessageEl."""
+    response = client.post("/api/recommend", json=NO_MATCH_PAYLOAD)
+    data = response.get_json()
+    assert "message" in data, (
+        "API must return a 'message' field when projects is empty "
+        "so the JS can populate emptyMessageEl without a null-ref error"
+    )
+    assert isinstance(data["message"], str)
+    assert len(data["message"]) > 0
+
+
+def test_match_after_no_match_returns_projects(client):
+    """After a zero-result query, a valid query must return projects normally."""
+    # First call — no match (simulates the bug scenario step 2)
+    r1 = client.post("/api/recommend", json=NO_MATCH_PAYLOAD)
+    assert r1.get_json()["projects"] == []
+
+    # Second call — valid match (simulates step 3-4)
+    r2 = client.post("/api/recommend", json=MATCH_PAYLOAD)
+    data = r2.get_json()
+    assert r2.status_code == 200
+    assert len(data["projects"]) > 0, (
+        "Valid query after a no-match query must still return projects — "
+        "the server must not carry state between requests"
+    )
+
+
+def test_match_after_no_match_has_no_message(client):
+    """A successful result must NOT include a blocking 'message' field
+    (or if it does, projects must be non-empty — they must not both be set
+    in a way that would cause the empty-state branch to render)."""
+    client.post("/api/recommend", json=NO_MATCH_PAYLOAD)
+    r2 = client.post("/api/recommend", json=MATCH_PAYLOAD)
+    data = r2.get_json()
+    # Either no message, or projects are present (non-empty result wins)
+    if "message" in data:
+        assert len(data["projects"]) > 0, (
+            "If 'message' is present alongside projects, projects must be "
+            "non-empty so renderResults takes the success branch"
+        )
+
+
+def test_repeated_no_match_queries_are_consistent(client):
+    """Multiple consecutive no-match queries must all return empty lists."""
+    for _ in range(3):
+        r = client.post("/api/recommend", json=NO_MATCH_PAYLOAD)
+        assert r.get_json()["projects"] == []
+
+
+def test_repeated_match_queries_are_consistent(client):
+    """Multiple consecutive match queries must all return the same projects."""
+    results = []
+    for _ in range(3):
+        r = client.post("/api/recommend", json=MATCH_PAYLOAD)
+        results.append([p["id"] for p in r.get_json()["projects"]])
+    assert results[0] == results[1] == results[2], (
+        "Recommendation results must be deterministic across calls"
+    )
+
+
+def test_alternating_no_match_and_match(client):
+    """Alternating no-match / match calls must each return the correct state."""
+    for i in range(4):
+        if i % 2 == 0:
+            r = client.post("/api/recommend", json=NO_MATCH_PAYLOAD)
+            assert r.get_json()["projects"] == [], f"Iteration {i}: expected empty"
+        else:
+            r = client.post("/api/recommend", json=MATCH_PAYLOAD)
+            assert len(r.get_json()["projects"]) > 0, f"Iteration {i}: expected results"
+
+
+# ---------------------------------------------------------------------------
+# HTML landmark presence — JS selectors must resolve
+# ---------------------------------------------------------------------------
+
+def test_results_section_present(client):
+    """#results-section must exist — setLoadingState targets it."""
+    r = client.get("/")
+    assert b'id="results-section"' in r.data
+
+
+def test_results_loading_present(client):
+    """#results-loading must exist — setLoadingState shows/hides it."""
+    r = client.get("/")
+    assert b'id="results-loading"' in r.data
+
+
+def test_results_empty_present(client):
+    """#results-empty must exist — renderResults shows it on zero results."""
+    r = client.get("/")
+    assert b'id="results-empty"' in r.data
+
+
+def test_results_grid_present(client):
+    """#results-grid must exist — renderResults populates it."""
+    r = client.get("/")
+    assert b'id="results-grid"' in r.data
+
+
+def test_empty_message_element_present(client):
+    """#empty-message must exist — renderResults sets its textContent."""
+    r = client.get("/")
+    assert b'id="empty-message"' in r.data, (
+        "#empty-message element is missing; renderResults will throw a "
+        "null-reference error when trying to set emptyMessageEl.textContent"
+    )
+
+
+def test_results_section_initially_hidden(client):
+    """results-section must start hidden (display:none inline style)."""
+    r = client.get("/")
+    # The template sets style="display:none;" on the section
+    assert b'id="results-section"' in r.data
+    # Check the inline style is present in the same element
+    html = r.data.decode("utf-8")
+    idx = html.find('id="results-section"')
+    # Grab a window of chars around the element opening tag
+    snippet = html[max(0, idx - 10): idx + 120]
+    assert "display:none" in snippet or "display: none" in snippet, (
+        "results-section must have display:none so it is hidden before the "
+        "first search; the JS reveals it in setLoadingState"
+    )
+
+
+# ---------------------------------------------------------------------------
+# script.js contains the fixed functions
+# ---------------------------------------------------------------------------
+
+def test_script_js_served(client):
+    r = client.get("/static/script.js")
+    assert r.status_code == 200
+
+
+def test_script_js_clears_results_grid_on_loading(client):
+    """setLoadingState must clear resultsGrid.innerHTML when isLoading=true."""
+    r = client.get("/static/script.js")
+    js = r.data.decode("utf-8")
+    # The fix sets resultsGrid.innerHTML = "" inside the isLoading branch
+    assert 'resultsGrid.innerHTML = ""' in js or "resultsGrid.innerHTML=''" in js, (
+        "setLoadingState must set resultsGrid.innerHTML to '' when isLoading "
+        "is true so stale cards from a previous search are removed immediately"
+    )
+
+
+def test_script_js_hides_empty_state_on_loading(client):
+    """setLoadingState must hide resultsEmptyEl when starting a new search."""
+    r = client.get("/static/script.js")
+    js = r.data.decode("utf-8")
+    assert 'resultsEmptyEl.style.display = "none"' in js, (
+        "setLoadingState must hide resultsEmptyEl so the No Projects Found "
+        "card does not remain visible during a new search"
+    )
+
+
+def test_script_js_render_results_resets_grid_display(client):
+    """renderResults must reset grid display before populating it."""
+    r = client.get("/static/script.js")
+    js = r.data.decode("utf-8")
+    assert 'resultsGrid.innerHTML = ""' in js, (
+        "renderResults must clear innerHTML before appending new cards"
+    )
+
+
+def test_script_js_render_results_guards_empty_message_el(client):
+    """renderResults must guard emptyMessageEl with a null check."""
+    r = client.get("/static/script.js")
+    js = r.data.decode("utf-8")
+    # The fix wraps emptyMessageEl.textContent assignment in an if check
+    assert "if (emptyMessageEl)" in js, (
+        "renderResults must guard emptyMessageEl against null to prevent "
+        "TypeError when the element is unexpectedly absent"
+    )