Merge pull request #619 from smcv/symlink-idempotent

Add documentation and test coverage for #577

bwrap.xml

@@ -364,7 +364,16 @@
     </varlistentry>
     <varlistentry>
       <term><option>--symlink <arg choice="plain">SRC</arg> <arg choice="plain">DEST</arg></option></term>
-      <listitem><para>Create a symlink at <arg choice="plain">DEST</arg> with target <arg choice="plain">SRC</arg></para></listitem>
+      <listitem>
+        <para>Create a symlink at <arg choice="plain">DEST</arg> with target
+          <arg choice="plain">SRC</arg>.</para>
+        <para>Since version 0.9.0, it is not considered to be an error if
+          <arg choice="plain">DEST</arg> already exists as a symbolic link and its
+          target is exactly <arg choice="plain">SRC</arg>.</para>
+        <para>Before version 0.9.0, if <arg choice="plain">DEST</arg> already
+          existed, this would be treated as an error (even if its target
+          was identical to <arg choice="plain">SRC</arg>).</para>
+      </listitem>
     </varlistentry>
     <varlistentry>
       <term><option>--chmod <arg choice="plain">OCTAL</arg> <arg choice="plain">PATH</arg></option></term>

tests/test-run.sh

@@ -76,6 +76,21 @@ for ALT in "" "--unshare-user-try" "--unshare-pid" "--unshare-user-try --unshare
     ok "can bind a destination over a symlink"
 done
 
+# Test symlink behaviour
+rm -f ./symlink
+$RUN --ro-bind / / --bind "$(pwd)" "$(pwd)" --symlink /dev/null "$(pwd)/symlink" true >&2
+readlink ./symlink > target.txt
+assert_file_has_content target.txt /dev/null
+ok "--symlink works"
+$RUN --ro-bind / / --bind "$(pwd)" "$(pwd)" --symlink /dev/null "$(pwd)/symlink" true >&2
+ok "--symlink is idempotent"
+if $RUN --ro-bind / / --bind "$(pwd)" "$(pwd)" --symlink /dev/full "$(pwd)/symlink" true 2>err.txt; then
+    fatal "creating a conflicting symlink should have failed"
+else
+    assert_file_has_content err.txt "Can't make symlink .*: existing destination is /dev/null"
+fi
+ok "--symlink doesn't overwrite a conflicting symlink"
+
 # Test devices
 $RUN --unshare-pid --dev /dev ls -al /dev/{stdin,stdout,stderr,null,random,urandom,fd,core} >/dev/null
 ok "all expected devices were created"