godoc: re-add test for ignoring //line comments in source code

The original CL 84050044 added a test case, and it happened to be
in between various CLI test cases. CLI support was removed from
x/tools/cmd/godoc in CL 141397, as part of golang/go#25443.
Re-add a test case for this behavior to prevent regressions.

Updates golang/go#32092
Updates golang/go#25443
Updates golang/go#5247

Change-Id: I0cea74cfe40d120e398a9005676134c5bad6136c
Reviewed-on: https://go-review.googlesource.com/c/tools/+/177737
Reviewed-by: Robert Griesemer <gri@golang.org>

godoc/parser.go

@@ -53,7 +53,7 @@ func (c *Corpus) parseFile(fset *token.FileSet, filename string, mode parser.Mod
 	}
 
 	// Temporary ad-hoc fix for issue 5247.
-	// TODO(gri) Remove this in favor of a better fix, eventually (see issue 7702).
+	// TODO(gri,dmitshur) Remove this in favor of a better fix, eventually (see issue 32092).
 	replaceLinePrefixCommentsWithBlankLine(src)
 
 	return parser.ParseFile(fset, filename, src, mode)

godoc/server_test.go

@@ -46,3 +46,24 @@ package main`}))
 		t.Error("pInfo.FSet = nil; want non-nil.")
 	}
 }
+
+func TestIssue5247(t *testing.T) {
+	const packagePath = "example.com/p"
+	c := NewCorpus(mapfs.New(map[string]string{
+		"src/" + packagePath + "/p.go": `package p
+
+//line notgen.go:3
+// F doc //line 1 should appear
+// line 2 should appear
+func F()
+//line foo.go:100`})) // No newline at end to check corner cases.
+
+	srv := &handlerServer{
+		p: &Presentation{Corpus: c},
+		c: c,
+	}
+	pInfo := srv.GetPageInfo("/src/"+packagePath, packagePath, 0, "linux", "amd64")
+	if got, want := pInfo.PDoc.Funcs[0].Doc, "F doc //line 1 should appear\nline 2 should appear\n"; got != want {
+		t.Errorf("pInfo.PDoc.Funcs[0].Doc = %q; want %q", got, want)
+	}
+}