From c15af086fd9aeebe48c9742d7e3d26d3923d095e Mon Sep 17 00:00:00 2001
From: Paul Gschwendtner <paulgschwendtner@gmail.com>
Date: Sun, 28 Apr 2019 00:49:39 +0200
Subject: [PATCH] Fix compressed source-maps have non-terminated segments

Currently when UglifyJS compresses a given input file that comes
with a source-map, but the source-map does not have mappings for
all code parts in the input file. e.g. the input file has been generated
and some specific code-parts have been generated and are not
originating from any source-file.

In that case if mappings before the "generated code" are collected, and
the original file location for the "generated code" is determined after previous
mappings for the same line have been recorded, UglifyJS just ignores the fact that
there is no original location and the previous segment is not terminated. This causes
the "generated code" incorrectly to be mapped to the previous segment/
original source location.
---
 lib/sourcemap.js                | 22 +++++++++++++----
 test/input/pr-3040/expect.js    |  2 +-
 test/input/pr-3040/input.js     |  2 +-
 test/input/pr-3040/input.js.map |  2 +-
 test/mocha/sourcemaps.js        | 44 +++++++++++++++++++++++++++++++++
 5 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/lib/sourcemap.js b/lib/sourcemap.js
index 2feec45d..72c4709a 100644
--- a/lib/sourcemap.js
+++ b/lib/sourcemap.js
@@ -70,12 +70,27 @@ function SourceMap(options) {
     return {
         add: function(source, gen_line, gen_col, orig_line, orig_col, name) {
             var map = maps && maps[source];
+            var generatedPos = {
+                line: gen_line + options.dest_line_diff,
+                column: gen_col
+            };
             if (map) {
                 var info = map.originalPositionFor({
                     line: orig_line,
                     column: orig_col
                 });
-                if (info.source === null) return;
+                if (info.source === null) {
+                    if (generatedPos.column !== 0) {
+                        generator.
+                        generator.addMapping({
+                            generated: generatedPos,
+                            original: null,
+                            source: null,
+                            name: null
+                        });
+                    }
+                    return;
+                }
                 source = info.source;
                 orig_line = info.line;
                 orig_col = info.column;
@@ -84,10 +99,7 @@ function SourceMap(options) {
             generator.addMapping({
                 name: name,
                 source: source,
-                generated: {
-                    line: gen_line + options.dest_line_diff,
-                    column: gen_col
-                },
+                generated: generatedPos,
                 original: {
                     line: orig_line + options.orig_line_diff,
                     column: orig_col
diff --git a/test/input/pr-3040/expect.js b/test/input/pr-3040/expect.js
index b911f3f8..1b8674eb 100644
--- a/test/input/pr-3040/expect.js
+++ b/test/input/pr-3040/expect.js
@@ -1,2 +1,2 @@
 function _toConsumableArray(arr){if(Array.isArray(arr)){for(var i=0,arr2=Array(arr.length);i<arr.length;i++){arr2[i]=arr[i]}return arr2}else{return Array.from(arr)}}var _require=require("bar"),foo=_require.foo;var _require2=require("world"),hello=_require2.hello;foo.x.apply(foo,_toConsumableArray(foo.y(hello.z)));
-//# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbImlucHV0Mi5qcyJdLCJuYW1lcyI6WyJyZXF1aXJlIiwiYXJyIl0sIm1hcHBpbmdzIjoiMEpBQWNBLEtBQVFDIiwic291cmNlc0NvbnRlbnQiOlsiY29uc3Qge2Zvb30gPSByZXF1aXJlKFwiYmFyXCIpO1xuY29uc3Qge2hlbGxvfSA9IHJlcXVpcmUoXCJ3b3JsZFwiKTtcblxuZm9vLngoLi4uZm9vLnkoaGVsbG8ueikpO1xuIl19
+//# sourceMappingURL=data:application/json;charset=utf-8;base64,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
diff --git a/test/input/pr-3040/input.js b/test/input/pr-3040/input.js
index 6515dcbd..39397953 100644
--- a/test/input/pr-3040/input.js
+++ b/test/input/pr-3040/input.js
@@ -8,4 +8,4 @@ var _require2 = require("world"),
 
 foo.x.apply(foo, _toConsumableArray(foo.y(hello.z)));
 
-//# sourceMappingURL=input.js.map
\ No newline at end of file
+//# sourceMappingURL=input.js.map
diff --git a/test/input/pr-3040/input.js.map b/test/input/pr-3040/input.js.map
index f0883e22..77ddeb28 100644
--- a/test/input/pr-3040/input.js.map
+++ b/test/input/pr-3040/input.js.map
@@ -1 +1 @@
-{"version":3,"sources":["input2.js"],"names":["require","foo","hello","x","apply","_toConsumableArray","y","z"],"mappings":"kLAAcA,QAAQ,OAAfC,aAAAA,kBACSD,QAAQ,SAAjBE,gBAAAA,MAEPD,IAAIE,EAAJC,MAAAH,IAAAI,mBAASJ,IAAIK,EAAEJ,MAAMK","sourcesContent":["const {foo} = require(\"bar\");\nconst {hello} = require(\"world\");\n\nfoo.x(...foo.y(hello.z));\n"]}
\ No newline at end of file
+{"version":3,"sources":["input2.js"],"names":[],"mappings":";;AAAA,IAAc;CAAP;;AACP,IAAgB;CAAT;;AAEP,iBAAM,mBAAG","sourcesContent":["const {foo} = require(\"bar\");\nconst {hello} = require(\"world\");\n\nfoo.x(...foo.y(hello.z));\n"]}
diff --git a/test/mocha/sourcemaps.js b/test/mocha/sourcemaps.js
index ccaa68e1..c2a5bd0a 100644
--- a/test/mocha/sourcemaps.js
+++ b/test/mocha/sourcemaps.js
@@ -1,6 +1,7 @@
 var assert = require("assert");
 var readFileSync = require("fs").readFileSync;
 var SourceMapConsumer = require("source-map").SourceMapConsumer;
+var SourceMapGenerator = require("source-map").SourceMapGenerator;
 var UglifyJS = require("../..");
 
 function read(path) {
@@ -284,5 +285,48 @@ describe("sourcemaps", function() {
                 assert.ok(pos.line <= 2, msg);
             });
         });
+
+        it("Should preserve unmapped segments in output source map", function() {
+            var generator = new SourceMapGenerator();
+
+            generator.addMapping({
+                source: "source.ts",
+                generated: {line: 1, column: 0},
+                original: {line: 1, column: 0},
+            });
+
+            generator.addMapping({
+                source: null,
+                original: null,
+                generated: {line: 1, column: 38}
+            });
+
+            generator.addMapping({
+                source: "source.ts",
+                generated: {line: 1, column: 51},
+                original: {line: 2, column: 0},
+            });
+
+            // Everything except the "say('hello');" part is mapped to "source.ts". The "say"
+            // function call is not mapped to any original source location. e.g. this can
+            // happen when a code transformer inserts generated code in between existing code.
+            var inputFile = "function say(msg) {console.log(msg)};say('hello');process.exit(1);";
+            var result = UglifyJS.minify(inputFile, {
+                sourceMap: {
+                    content: JSON.parse(generator.toString())
+                }
+            });
+
+            var transformedMap = new SourceMapConsumer(result.map);
+            var hasMappedSource = true;
+
+            for (let i = 0; i < result.code.length; i++) {
+                var info = transformedMap.originalPositionFor({line: 1, column: i});
+                hasMappedSource = hasMappedSource && !!info.source;
+            }
+
+            assert.equal(hasMappedSource, false, "Expected transformed source map to preserve the " +
+              "mapping without original source location");
+        });
     });
 });