diagnose(shell): record the projection shape behind a discarded selection (#156)

.github/workflows/conpty-compat.yml

@@ -213,3 +213,33 @@ jobs:
           retention-days: 14
           if-no-files-found: warn
           path: node-contract-timing.json
+
+  windows-2025-actions-repeat:
+    # Bounded reproduction for #156 / #99 / #73: repeats the clipboard and
+    # geometry scenarios on the hosted image so the selection-discard
+    # diagnostics can be ordered against the scenario phase timeline.
+    runs-on: windows-2025
+    timeout-minutes: 60
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - uses: actions/setup-python@6d4fd22b20465ccc0f7354476588e8df7c9ca0e0 # v7.1.0
+        with:
+          python-version: '3.12'
+      - name: Configure
+        run: cmake -S . -B build -DCMAKE_BUILD_TYPE=Release
+      - name: Build
+        run: cmake --build build --config Release --parallel 2
+      - name: Prepare hosted Windows shell prerequisites
+        run: python -m tools.prepare_hosted_shells --out local/hosted-shells
+      - name: Repeat the actions scenarios
+        env:
+          TERMFORGE_REQUIRE_SYSTEM_CLIPBOARD: '1'
+        run: ctest --test-dir build -C Release -R "text_actions|selection_context" --repeat until-fail:20 --output-on-failure
+      - name: Preserve repeat evidence
+        if: always()
+        uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7.0.2
+        with:
+          name: actions-repeat-evidence
+          retention-days: 14
+          if-no-files-found: warn
+          path: build/test-artifacts/

experiments/core/selection_test.cpp

@@ -188,7 +188,7 @@ static void empty_stale_and_capacity_boundaries() {
 }
 
 static std::vector<std::string> observed_discards;
-static void observe_discard(const char* reason, size_t) { observed_discards.push_back(reason ? reason : ""); }
+static void observe_discard(const TextSelection::DiscardReport& report) { observed_discards.push_back(report.reason ? report.reason : ""); }
 static void discard_reasons_are_reported() {
     Parser p(2, 6, 2);
     p.feed("ONETWO\r\nTHREE");

experiments/core/text_selection.hpp

@@ -14,7 +14,15 @@ class TextSelection {
     // Diagnostics only: never changes behaviour. A consumer may install a hook to
     // learn why a reconciled selection was discarded; the hook runs synchronously
     // on the caller's thread and must not reenter selection or the document.
-    using DiscardObserver = void (*)(const char* reason, size_t row);
+    // Diagnostics only: the report names the branch and, where it helps, the
+    // row plus the saved/current projection shape that differed.
+    struct DiscardReport {
+        const char* reason = "";
+        size_t row = 0;
+        size_t saved_bytes = 0, current_bytes = 0;
+        size_t saved_columns = 0, current_columns = 0;
+    };
+    using DiscardObserver = void (*)(const DiscardReport&);
     static void set_discard_observer(DiscardObserver observer) { discard_observer_ = observer; }
 private:
     static inline DiscardObserver discard_observer_ = nullptr;
@@ -40,10 +48,13 @@ class TextSelection {
         return c >= 0x80 || (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') ||
                (c >= '0' && c <= '9') || c == '_' || c == '-' ? 0 : 2;
     }
-    bool invalidate(const char* reason, size_t row = 0) {
-        if (discard_observer_) discard_observer_(reason, row);
+    bool invalidate(const DiscardReport& report) {
+        if (discard_observer_) discard_observer_(report);
         clear(); invalidated_ = true; return false;
     }
+    bool invalidate(const char* reason, size_t row = 0) {
+        DiscardReport report; report.reason = reason; report.row = row; return invalidate(report);
+    }
 public:
     static constexpr size_t maximum_snapshot_bytes = 8 * 1024 * 1024;
     void clear() { range_.reset(); saved_.clear(); invalidated_ = false; }
@@ -92,7 +103,12 @@ class TextSelection {
                 // The last row at column zero is an excluded half-open
                 // endpoint. Its own following break is outside the copy.
                 const bool compare_boundary = i + 1 != saved_.size() || range_->end.column != 0;
-                if (!same_text(saved, current, compare_boundary)) return invalidate("row-text-changed", i);
+                if (!same_text(saved, current, compare_boundary)) {
+                    DiscardReport report; report.reason = "row-text-changed"; report.row = i;
+                    report.saved_bytes = saved.projection.text.size(); report.current_bytes = current.projection.text.size();
+                    report.saved_columns = saved.columns; report.current_columns = current.columns;
+                    return invalidate(report);
+                }
                 saved = std::move(current);
             }
         }

experiments/shell/shell.cpp

@@ -40,13 +40,15 @@ std::string selection_diag_path() {
     return value ? std::string(value) : std::string{};
 #endif
 }
-void selection_discard_diagnostic(const char* reason, size_t row) {
+void selection_discard_diagnostic(const termforge::TextSelection::DiscardReport& report) {
     static const std::string path = selection_diag_path();
     if (path.empty()) return;
     std::ofstream stream(path, std::ios::app);
     if (!stream) return;
-    stream << "{\"schema\":\"termforge-selection-discard-v1\",\"reason\":\"" << reason
-           << "\",\"row\":" << row << ",\"t_ms\":" << GetTickCount64() << "}\n";
+    stream << "{\"schema\":\"termforge-selection-discard-v1\",\"reason\":\"" << report.reason
+           << "\",\"row\":" << report.row << ",\"saved_bytes\":" << report.saved_bytes
+           << ",\"current_bytes\":" << report.current_bytes << ",\"saved_columns\":" << report.saved_columns
+           << ",\"current_columns\":" << report.current_columns << ",\"t_ms\":" << GetTickCount64() << "}\n";
 }
 void install_selection_diagnostic_once() {
     static std::once_flag once;