fix(sankey): derive effective node.pad clamp from layout geometry

draftlogs/7977_fix.md

@@ -0,0 +1 @@
+ - Fix `node.pad` reduction warning so it derives the effective (post-clamp) padding from the laid-out node geometry instead of reading `sankey.nodePadding()`, which since @plotly/d3-sankey 0.12.x returns the configured value and made the warning never fire [[#7977](https://github.com/plotly/plotly.js/pull/7977)]

src/traces/sankey/render.js

@@ -90,8 +90,30 @@ function sankeyModel(layout, d, traceIndex) {
 
     var graph = sankey();
 
-    if(sankey.nodePadding() < nodePad) {
-        Lib.warn('node.pad was reduced to ', sankey.nodePadding(), ' to fit within the figure.');
+    // Derive the effective (post-clamp) node padding from the laid-out node
+    // geometry instead of reading it back through `sankey.nodePadding()`.
+    // In @plotly/d3-sankey@0.7.x that getter returned the clamped value after
+    // the layout ran, but since 0.12.x it returns the user-configured value
+    // (upstream split `dy` from `py`), so a getter-based check would never
+    // fire. Measuring the smallest vertical gap between consecutive nodes in
+    // any one column is version-independent. See #7832.
+    var effectivePad = nodePad;
+    var columns = {};
+    graph.nodes.forEach(function(node) {
+        var col = Math.round(node.x0);
+        if(!columns[col]) columns[col] = [];
+        columns[col].push([node.y0, node.y1]);
+    });
+    for(var key in columns) {
+        var column = columns[key].sort(function(a, b) { return a[0] - b[0]; });
+        for(var n = 1; n < column.length; n++) {
+            var gap = column[n][0] - column[n - 1][1];
+            if(gap < effectivePad) effectivePad = gap;
+        }
+    }
+
+    if(effectivePad < nodePad) {
+        Lib.warn('node.pad was reduced to ', effectivePad, ' to fit within the figure.');
     }
 
     // Counters for nested loops

test/jasmine/tests/sankey_test.js

@@ -95,8 +95,88 @@ describe('sankey tests', function () {
         });
     });
 
+
     describe('sankey global defaults', function () {
         it('should not coerce trace opacity', function () {
+
+
+    describe('node.pad reduction warning', function() {
+        // The warning must be driven by the effective (post-clamp) padding,
+        // not by reading `sankey.nodePadding()` back, which since
+        // @plotly/d3-sankey@0.12.x returns the configured value instead of
+        // the clamped one - see #7832.
+        var padMock = {
+            data: [{
+                type: 'sankey',
+                node: {
+                    label: Array.from({length: 24}, function(_, i) { return 'n' + i; }),
+                    pad: 30,
+                    thickness: 10
+                },
+                link: {
+                    // star topology: one source feeding 24 sinks puts all 24
+                    // sink nodes in a single column, so a small figure must
+                    // clamp the padding
+                    source: Array.from({length: 24}, function() { return 0; }),
+                    target: Array.from({length: 24}, function(_, i) { return i + 1; }),
+                    value: Array.from({length: 24}, function() { return 1; })
+                }
+            }],
+            layout: {
+                width: 500,
+                height: 500,
+                margin: {l: 10, r: 10, t: 10, b: 10}
+            }
+        };
+
+        it('warns when the figure is too small for node.pad', function(done) {
+            var warnings = [];
+            spyOn(Lib, 'warn').and.callFake(function() {
+                // collect all arguments, as Lib.warn is variadic
+                warnings.push(Array.prototype.slice.call(arguments));
+            });
+
+            var fig = Lib.extendDeep({}, padMock);
+            fig.layout.width = 200;
+            fig.layout.height = 100;
+            var gd = createGraphDiv();
+            Plotly.newPlot(gd, fig)
+                .then(function() {
+                    expect(warnings.length).toEqual(1);
+                    expect(warnings[0][0]).toBe('node.pad was reduced to ');
+                    expect(warnings[0][1]).toBeLessThan(30);
+                    return Plotly.purge(gd);
+                })
+                .then(function() { destroyGraphDiv(gd); })
+                .then(done, done.fail);
+        });
+
+        it('does not warn when the figure fits node.pad', function(done) {
+            var warnings = [];
+            spyOn(Lib, 'warn').and.callFake(function() {
+                // collect all arguments, as Lib.warn is variadic
+                warnings.push(Array.prototype.slice.call(arguments));
+            });
+
+            var fig = Lib.extendDeep({}, padMock);
+            fig.layout.width = 480;
+            fig.layout.height = 1000;
+            // keep the sink column short enough that pad=30 always fits
+            fig.data[0].node.label = Array.from({length: 8}, function(_, i) { return 'n' + i; });
+            fig.data[0].link.source = Array.from({length: 7}, function() { return 0; });
+            fig.data[0].link.target = Array.from({length: 7}, function(_, i) { return i + 1; });
+            fig.data[0].link.value = Array.from({length: 7}, function() { return 1; });
+            var gd = createGraphDiv();
+            Plotly.newPlot(gd, fig)
+                .then(function() {
+                    expect(warnings.length).toEqual(0);
+                    return Plotly.purge(gd);
+                })
+                .then(function() { destroyGraphDiv(gd); })
+                .then(done, done.fail);
+        });
+    });
+ (fix(sankey): derive effective node.pad clamp from layout geometry)
             var gd = Lib.extendDeep({}, mock);
 
             supplyAllDefaults(gd);