From e820f973ad8ca99822be69c927c7d7bf6a89f54e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Johannes=20K=C3=B6ster?= <johannes.koester@tu-dortmund.de>
Date: Thu, 31 Mar 2022 13:33:33 +0200
Subject: [PATCH] fix: do not remove existing temp files in case of dryrun
 (#1543)

---
 snakemake/dag.py                              |  7 +++++--
 tests/test_github_issue1542/Snakefile         | 20 +++++++++++++++++++
 tests/test_github_issue1542/a.txt             |  0
 .../expected-results/a.txt                    |  0
 tests/tests.py                                |  4 ++++
 5 files changed, 29 insertions(+), 2 deletions(-)
 create mode 100644 tests/test_github_issue1542/Snakefile
 create mode 100644 tests/test_github_issue1542/a.txt
 create mode 100644 tests/test_github_issue1542/expected-results/a.txt

diff --git a/snakemake/dag.py b/snakemake/dag.py
index eed5d0059..6daa8cbb5 100755
--- a/snakemake/dag.py
+++ b/snakemake/dag.py
@@ -639,8 +639,11 @@ def unneeded_files():
                 yield from filterfalse(partial(needed, job), tempfiles)
 
         for f in unneeded_files():
-            logger.info("Removing temporary output file {}.".format(f))
-            f.remove(remove_non_empty_dir=True)
+            if self.dryrun:
+                logger.info(f"Would remove temporary output {f}")
+            else:
+                logger.info("Removing temporary output {}.".format(f))
+                f.remove(remove_non_empty_dir=True)
 
     def handle_log(self, job, upload_remote=True):
         for f in job.log:
diff --git a/tests/test_github_issue1542/Snakefile b/tests/test_github_issue1542/Snakefile
new file mode 100644
index 000000000..221fec1bc
--- /dev/null
+++ b/tests/test_github_issue1542/Snakefile
@@ -0,0 +1,20 @@
+# Snakefile
+rule all:
+    input:
+        "b.txt",
+
+
+rule a:
+    output:
+        temp("a.txt"),
+    shell:
+        "touch a.txt"
+
+
+rule b:
+    input:
+        "a.txt",
+    output:
+        "b.txt",
+    shell:
+        "touch b.txt"
diff --git a/tests/test_github_issue1542/a.txt b/tests/test_github_issue1542/a.txt
new file mode 100644
index 000000000..e69de29bb
diff --git a/tests/test_github_issue1542/expected-results/a.txt b/tests/test_github_issue1542/expected-results/a.txt
new file mode 100644
index 000000000..e69de29bb
diff --git a/tests/tests.py b/tests/tests.py
index bd5702a0e..515e780fa 100644
--- a/tests/tests.py
+++ b/tests/tests.py
@@ -1580,3 +1580,7 @@ def test_pipe_depend():
 @skip_on_windows  # no pipe support on windows
 def test_pipe_depend_target_file():
     run(dpath("test_pipe_depend"), targets=["test.txt"], shouldfail=True)
+
+
+def test_github_issue1542():
+    run(dpath("test_github_issue1542"), dryrun=True)