fix: carry trimStart and trimEnd into the outro and intro

src/MagicString.ts

@@ -1248,7 +1248,10 @@ export default class MagicString {
       chunk = chunk.previous
     } while (chunk)
 
-    return false
+    // like Chunk#trimEnd, carry on into the intro once everything after it has
+    // been trimmed away, since the intro is then the end of the string
+    this.intro = this.intro.replace(rx, '')
+    return this.intro.length > 0
   }
 
   /**
@@ -1288,7 +1291,10 @@ export default class MagicString {
       chunk = chunk.next
     } while (chunk)
 
-    return false
+    // like Chunk#trimStart, carry on into the outro once everything before it
+    // has been trimmed away, since the outro is then the start of the string
+    this.outro = this.outro.replace(rx, '')
+    return this.outro.length > 0
   }
 
   /**

test/Bundle.test.ts

@@ -1124,6 +1124,26 @@ describe('bundle', () => {
       b.trimEnd()
       assert.equal(b.toString(), 'abc   ;')
     })
+
+    it('should stop trimStart at a blank source that still has appended content', () => {
+      const b = new Bundle()
+
+      b.addSource({ content: new MagicString('   ').append('X') })
+      b.addSource({ content: new MagicString('  Y') })
+
+      b.trimStart()
+      assert.equal(b.toString(), 'X\n  Y')
+    })
+
+    it('should stop trimEnd at a blank source that still has prepended content', () => {
+      const b = new Bundle()
+
+      b.addSource({ content: new MagicString('Y  ') })
+      b.addSource({ content: new MagicString('   ').prepend('X') })
+
+      b.trimEnd()
+      assert.equal(b.toString(), 'Y  \nX')
+    })
   })
 
   describe('toString', () => {

test/MagicString.test.ts

@@ -2378,6 +2378,20 @@ describe('magicString', () => {
       assert.equal(s.toString(), 'x abc')
     })
 
+    it('should carry trimStart into the global outro when nothing comes before it', () => {
+      const s = new MagicString('   ')
+      s.append(' x ')
+      s.trimStart()
+      assert.equal(s.toString(), 'x ')
+    })
+
+    it('should carry trimEnd into the global intro when nothing comes after it', () => {
+      const s = new MagicString('   ')
+      s.prepend(' x ')
+      s.trimEnd()
+      assert.equal(s.toString(), ' x')
+    })
+
     it('should trim original content', () => {
       assert.equal(new MagicString('   abcdefghijkl   ').trim().toString(), 'abcdefghijkl')
       assert.equal(new MagicString('   abcdefghijkl').trim().toString(), 'abcdefghijkl')