fix: decompression fails with multiple apt.install calls (#72)

MODULE.bazel

@@ -7,7 +7,7 @@ module(
 )
 
 bazel_dep(name = "bazel_skylib", version = "1.5.0")
-bazel_dep(name = "aspect_bazel_lib", version = "2.7.3")
+bazel_dep(name = "aspect_bazel_lib", version = "2.7.9")
 
 bazel_lib_toolchains = use_extension("@aspect_bazel_lib//lib:extensions.bzl", "toolchains")
 use_repo(bazel_lib_toolchains, "zstd_toolchains")

apt/private/package_index.bzl

@@ -5,31 +5,53 @@ load(":util.bzl", "util")
 def _fetch_package_index(rctx, url, dist, comp, arch, integrity):
     target_triple = "{dist}/{comp}/{arch}".format(dist = dist, comp = comp, arch = arch)
 
-    file_types = {"xz": ["xz", "--decompress"], "gz": ["gzip", "-d"]}
-    r = {"success": False, "integrity": None}
-
-    decompression_successful = False
-    for file_type, tool in file_types.items():
-        output = "{}/Packages.{}".format(target_triple, file_type)
-        r = rctx.download(
-            url = "{}/dists/{}/{}/binary-{}/Packages.{}".format(url, dist, comp, arch, file_type),
+    # See https://linux.die.net/man/1/xz and https://linux.die.net/man/1/gzip
+    #  --keep       -> keep the original file (Bazel might be still committing the output to the cache)
+    #  --force      -> overwrite the output if it exists
+    #  --decompress -> decompress
+    supported_extensions = {
+        "xz": ["xz", "--decompress", "--keep", "--force"],
+        "gz": ["gzip", "--decompress", "--keep", "--force"],
+    }
+
+    failed_attempts = []
+
+    for (ext, cmd) in supported_extensions.items():
+        output = "{}/Packages.{}".format(target_triple, ext)
+        dist_url = "{}/dists/{}/{}/binary-{}/Packages.{}".format(url, dist, comp, arch, ext)
+        download = rctx.download(
+            url = dist_url,
             output = output,
             integrity = integrity,
             allow_fail = True,
         )
-        if r.success:
-            re = rctx.execute(tool + [output])
-            if re.return_code == 0:
-                decompression_successful = True
+        decompress_r = None
+        if download.success:
+            decompress_r = rctx.execute(cmd + [output])
+            if decompress_r.return_code == 0:
+                integrity = download.integrity
                 break
 
-    if not r.success:
-        fail("unable to download package index")
+        failed_attempts.append((url, download, decompress_r))
 
-    if not decompression_successful:
-        fail("unable to decompress package index")
+    if len(failed_attempts) == len(supported_extensions):
+        attempt_messages = []
+        for (url, download, decompress) in failed_attempts:
+            reason = "unknown"
+            if not download.success:
+                reason = "Download failed. See warning above for details."
+            elif decompress.return_code != 0:
+                reason = "Decompression failed with non-zero exit code.\n\n{}\n{}".format(decompress.stderr, decompress.stdout)
 
-    return ("{}/Packages".format(target_triple), r.integrity)
+            attempt_messages.append("""\n*) Failed '{}'\n\n{}""".format(url, reason))
+
+        fail("""
+** Tried to download {} different package indices and all failed. 
+
+{}
+        """.format(len(failed_attempts), "\n".join(attempt_messages)))
+
+    return ("{}/Packages".format(target_triple), integrity)
 
 def _parse_package_index(state, contents, arch, root):
     last_key = ""
@@ -91,11 +113,11 @@ def _create(rctx, sources, archs):
             # on misconfigured HTTP servers)
             url = url.rstrip("/")
 
-            rctx.report_progress("Fetching package index: {}/{}".format(dist, arch))
+            rctx.report_progress("Fetching package index: {}/{} for {}".format(dist, comp, arch))
             (output, _) = _fetch_package_index(rctx, url, dist, comp, arch, "")
 
             # TODO: this is expensive to perform.
-            rctx.report_progress("Parsing package index: {}/{}".format(dist, arch))
+            rctx.report_progress("Parsing package index: {}/{} for {}".format(dist, comp, arch))
             _parse_package_index(state, rctx.read(output), arch, url)
 
     return struct(