bazelbuild/bazel

native patch fails to apply multi-file patches without file headers

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#10,267 opened on Nov 18, 2019

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 (4 comments) (1 reaction) (1 assignee)Java (25,384 stars) (4,465 forks)batch import
P2help wantedteam-ExternalDepstype: feature request

Description

patch(1) can apply the following patch, but the repository rule ctx's patch method can't:

--- a/newfile	1969-12-31 16:00:00.000000000 -0800
+++ b/newfile	2019-11-18 09:41:29.206408378 -0800
@@ -0,0 +1,2 @@
+I'm a new file
+hello, world
--- a/newfile2	1969-12-31 16:00:00.000000000 -0800
+++ b/newfile2	2019-11-18 09:46:48.146505886 -0800
@@ -0,0 +1,2 @@
+foo
+bar

Here's a test for PatchUtil:

diff --git a/src/test/java/com/google/devtools/build/lib/bazel/repository/PatchUtilTest.java b/src/test/java/com/google/devtools/build/lib/bazel/repository/PatchUtilTest.java
index 5fbcace554..e888c947bb 100644
--- a/src/test/java/com/google/devtools/build/lib/bazel/repository/PatchUtilTest.java
+++ b/src/test/java/com/google/devtools/build/lib/bazel/repository/PatchUtilTest.java
@@ -65,6 +65,29 @@ public class PatchUtilTest {
     assertThat(PatchUtil.readFile(newFile)).containsExactlyElementsIn(newFileContent);
   }
 
+  @Test
+  public void addTwoFiles() throws Exception {
+    Path patchFile =
+        scratch.file(
+            "/root/patchfile",
+            "--- a/newfile     1969-12-31 16:00:00.000000000 -0800",
+            "+++ b/newfile     2019-11-18 09:41:29.206408378 -0800",
+            "@@ -0,0 +1,2 @@",
+            "+I'm a new file",
+            "+hello, world",
+            "--- a/newfile2    1969-12-31 16:00:00.000000000 -0800",
+            "+++ b/newfile2    2019-11-18 09:46:48.146505886 -0800",
+            "@@ -0,0 +1,2 @@",
+            "+foo",
+            "+bar");
+
+    PatchUtil.apply(patchFile, 1, root);
+    assertThat(PatchUtil.readFile(root.getRelative("newfile")))
+        .containsExactlyElementsIn(ImmutableList.of("I'm a new file", "hello, world"));
+    assertThat(PatchUtil.readFile(root.getRelative("newfile2")))
+        .containsExactlyElementsIn(ImmutableList.of("foo", "bar"));
+  }
+
   @Test
   public void testAddOneLineFile() throws IOException, PatchFailedException {
     Path patchFile =

Contributor guide

Tech stack
java
Domain
build system
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
blocked
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Basic JavaBazel build systemPatch file format
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50
Research direction
Investigate the PatchUtil class in Bazel's repository package, specifically the method that parses diff patches. The issue shows that when applying a patch without file headers (just ' ' and '+++' lines) for multiple files, the parser fails. The provided test case in PatchUtilTest.java demonstrates the expected behavior. The fix should modify the parsing logic to handle the transition between multiple file patches correctly, similar to how the standalone `patch` command works.