sbang: fixes for sbang relocation

This fixes sbang relocation when using old binary packages, and updates
code in `relocate.py`.

There are really two places where we would want to handle an `sbang`
relocation:

1. Installing an old package that uses `sbang` with shebang lines like
   `#!/bin/bash $spack_prefix/sbang`
2. Installing a *new* package that uses `sbang` with shebang lines like
   `#!/bin/sh $install_tree/sbang`

The second case is actually handled automatically by our text relocation;
we don't need any special relocation logic for new shebangs, as our
relocation logic already changes references to the build-time
`install_tree` to point to the `install_tree` at intall-time.

Case 1 was not properly handled -- we would not take an old binary
package and point its shebangs at the new `sbang` location. This PR fixes
that and updates the code in `relocation.py` with some notes.

There is one more case we don't currently handle: if a binary package is
created from an installation in a short prefix that does *not* need
`sbang` and is installed to a long prefix that *does* need `sbang`, we
won't do anything. We should just patch the file as we would for a normal
install. In some upcoming PR we should probably change *all* `sbang`
relocation logic to be idempotent and to apply to any sort of shebang'd
file. Then we'd only have to worry about which files to `sbang`-ify at
install time and wouldn't need to care about these special cases.

1 files changed, 46 insertions, 0 deletions

diff --git a/lib/spack/spack/test/relocate.py b/lib/spack/spack/test/relocate.py
index f9e72ea0d7..e883bd44c5 100644
--- a/lib/spack/spack/test/relocate.py
+++ b/lib/spack/spack/test/relocate.py
@@ -12,6 +12,7 @@ import llnl.util.filesystem
 import pytest
 import spack.architecture
 import spack.concretize
+import spack.hooks.sbang as sbang
 import spack.paths
 import spack.relocate
 import spack.spec
@@ -401,3 +402,48 @@ def test_relocate_text_bin_raise_if_new_prefix_is_longer():
         spack.relocate.relocate_text_bin(
             ['item'], short_prefix, long_prefix, None, None, None
         )
+
+
+@pytest.mark.parametrize("sbang_line", [
+    "#!/bin/bash /path/to/orig/spack/bin/sbang",
+    "#!/bin/sh /orig/layout/root/bin/sbang"
+])
+def test_relocate_text_old_sbang(tmpdir, sbang_line):
+    """Ensure that old and new sbang styles are relocated."""
+
+    old_install_prefix = "/orig/layout/root/orig/install/prefix"
+    new_install_prefix = os.path.join(
+        spack.store.layout.root, "new", "install", "prefix"
+    )
+
+    # input file with an sbang line
+    original = """\
+{0}
+#!/usr/bin/env python
+
+/orig/layout/root/orig/install/prefix
+""".format(sbang_line)
+
+    # expected relocation
+    expected = """\
+{0}
+#!/usr/bin/env python
+
+{1}
+""".format(sbang.sbang_shebang_line(), new_install_prefix)
+
+    path = tmpdir.ensure("path", "to", "file")
+    with path.open("w") as f:
+        f.write(original)
+
+    spack.relocate.relocate_text(
+        [str(path)],
+        "/orig/layout/root",   spack.store.layout.root,
+        old_install_prefix,    new_install_prefix,
+        "/path/to/orig/spack", spack.paths.spack_root,
+        {
+            old_install_prefix: new_install_prefix
+        }
+    )
+
+    assert expected == open(str(path)).read()