Fix column-span clipping for indexed maps with line offsets

lib/source-map-consumer.js

@@ -918,6 +918,8 @@ class IndexedSourceMapConsumer extends SourceMapConsumer {
         }
       }
 
+      generatedPosition.line += lineShift;
+
       if (
         generatedPosition.lastColumn === Infinity &&
         nextSection &&
@@ -926,7 +928,6 @@ class IndexedSourceMapConsumer extends SourceMapConsumer {
         generatedPosition.lastColumn =
           nextSection.generatedOffset.generatedColumn - 2;
       }
-      generatedPosition.line += lineShift;
 
       return generatedPosition;
     }
@@ -961,6 +962,8 @@ class IndexedSourceMapConsumer extends SourceMapConsumer {
           }
         }
 
+        generatedPosition.line += lineShift;
+
         if (
           generatedPosition.lastColumn === Infinity &&
           nextSection &&
@@ -969,7 +972,6 @@ class IndexedSourceMapConsumer extends SourceMapConsumer {
           generatedPosition.lastColumn =
             nextSection.generatedOffset.generatedColumn - 2;
         }
-        generatedPosition.line += lineShift;
 
         return generatedPosition;
       });
@@ -994,6 +996,8 @@ class IndexedSourceMapConsumer extends SourceMapConsumer {
             }
           }
 
+          mapping.generatedLine += lineShift;
+
           if (
             mapping.lastGeneratedColumn === Infinity &&
             nextSection &&
@@ -1002,7 +1006,6 @@ class IndexedSourceMapConsumer extends SourceMapConsumer {
             mapping.lastGeneratedColumn =
               nextSection.generatedOffset.generatedColumn - 2;
           }
-          mapping.generatedLine += lineShift;
 
           aCallback.call(this, mapping);
         },

test/test-indexed-column-spans.js

@@ -0,0 +1,124 @@
+/* -*- Mode: js; js-indent-level: 2; -*- */
+/*
+ * Copyright Mozilla Foundation and contributors
+ * Licensed under the New BSD license. See LICENSE or:
+ * http://opensource.org/licenses/BSD-3-Clause
+ */
+
+const { SourceMapConsumer } = require("../lib/source-map-consumer");
+const { SourceMapGenerator } = require("../lib/source-map-generator");
+
+function section(offset, source, positions) {
+  const generator = new SourceMapGenerator();
+  for (const [column, generated] of positions.entries()) {
+    generator.addMapping({
+      source,
+      original: { line: 1, column },
+      generated,
+    });
+  }
+  return { offset, map: generator.toJSON() };
+}
+
+async function withSections(firstLine, nextLine, positions, callback) {
+  const consumer = await new SourceMapConsumer({
+    version: 3,
+    sections: [
+      section({ line: 4, column: 3 }, "first.js", positions),
+      section({ line: nextLine, column: 10 }, "second.js", [
+        { line: 1, column: 0 },
+      ]),
+    ],
+  });
+  try {
+    await callback(consumer, firstLine);
+  } finally {
+    consumer.destroy();
+  }
+}
+
+const readers = {
+  generatedPositionFor(consumer) {
+    return [
+      consumer.generatedPositionFor({
+        source: "first.js",
+        line: 1,
+        column: 0,
+      }),
+    ];
+  },
+  allGeneratedPositionsFor(consumer) {
+    return consumer.allGeneratedPositionsFor({
+      source: "first.js",
+      line: 1,
+      column: 0,
+    });
+  },
+  eachMapping(consumer) {
+    const mappings = [];
+    consumer.eachMapping(mapping => {
+      if (mapping.source === "first.js") {
+        mappings.push({
+          line: mapping.generatedLine,
+          column: mapping.generatedColumn,
+          lastColumn: mapping.lastGeneratedColumn,
+        });
+      }
+    });
+    return mappings;
+  },
+};
+
+for (const [name, read] of Object.entries(readers)) {
+  exports["test " + name + " clips spans after applying section line offsets"] =
+    async function (assert) {
+      // Cover both the section's first line (which has a column offset) and
+      // a later line (which only has a line offset).
+      for (const localLine of [1, 2]) {
+        await withSections(
+          4 + localLine,
+          3 + localLine,
+          [{ line: localLine, column: 2 }],
+          async (consumer, globalLine) => {
+            consumer.computeColumnSpans();
+            const positions = read(consumer);
+            assert.equal(positions.length, 1);
+            assert.equal(positions[0].line, globalLine);
+            assert.equal(positions[0].column, localLine === 1 ? 5 : 2);
+            assert.equal(positions[0].lastColumn, 9);
+          }
+        );
+      }
+    };
+
+  exports["test " + name + " preserves spans before a later section line"] =
+    async function (assert) {
+      await withSections(5, 5, [{ line: 1, column: 2 }], async consumer => {
+        consumer.computeColumnSpans();
+        assert.equal(read(consumer)[0].lastColumn, Infinity);
+      });
+    };
+
+  exports["test " + name + " preserves finite spans"] = async function (
+    assert
+  ) {
+    await withSections(
+      5,
+      4,
+      [
+        { line: 1, column: 2 },
+        { line: 1, column: 6 },
+      ],
+      async consumer => {
+        consumer.computeColumnSpans();
+        assert.equal(read(consumer)[0].lastColumn, 8);
+      }
+    );
+  };
+  exports["test " + name + " preserves uncomputed terminal spans"] =
+    async function (assert) {
+      await withSections(5, 4, [{ line: 1, column: 2 }], async consumer => {
+        assert.equal(read(consumer)[0].lastColumn, null);
+      });
+    };
+}