Update README.md

Note about not having ccache/sccache preinstalled in chroot.

README.md

@@ -63,6 +63,24 @@ GiB somehow).
 the build will fail if the limit is reached. If set to false, then the build
 will continue even if the limit is reached.
 
+## Soft-lock if `sccache` is preinstalled in chroot
+
+Apparently, some packages automatically use ccache/sccache if it is installed in
+the chroot, and in some cases, causes a soft-lock during a build. It is
+recommended to not have ccache/sccache preinstalled in the chroot and to just
+let the aur-helper-script install it when necessary.
+
+For example, when building `tenacity-git` with sccache preinstalled, the build
+will hang after the final build step. Apparently, killing the running `sccache`
+process stops the soft-lock in this case.
+
+## Preloading ccache/sccache
+
+This script expects ccache and sccache not to be installed in the chroot (for
+reasons as mentioned in the previous section) and ccache or sccache will be
+appended to a pkg's "other_deps" if a ccache or sccache directory is configured
+for it.
+
 # Setting up the AUR Helper
 
 The AUR Helper requires several things:
@@ -86,7 +104,9 @@ The `python-toml` package is required for the Python script to run.
 
 Use `/usr/bin/mkarchroot` to create your CHROOT in a directory.
 
-    mkarchroot $HOME/mychroot/root base base-devel ccache sccache cmake ninja
+    mkarchroot $HOME/mychroot/root base base-devel cmake ninja
+
+As noted earlier, it is better to NOT preinstall `ccache` and `sccache`.
 
 You must refer to the CHROOT as `$HOME/mychroot` if you used the same name as in
 the previous example.

update.py

@@ -741,6 +741,18 @@ def get_pkgbuild_version(
                     5,
                     f'{os.environ["HOME"]}/.cargo/git:/build/.cargo/git',
                 )
+            if len(pkg_state[pkg]["other_deps"]) != 0:
+                prefetch_result = prefetch_dependencies(
+                    pkg_state[pkg]["other_deps"], other_state
+                )
+                if prefetch_result != "fetched":
+                    log_print(
+                        "ERROR: Failed to prefetch deps {}".format(
+                            pkg_state[pkg]["other_deps"]
+                        ),
+                        other_state=other_state,
+                    )
+                    return False, None, None, None
             for dep in pkg_state[pkg]["other_deps"]:
                 dep_fullpath = get_latest_pkg(dep, "/var/cache/pacman/pkg")
                 if not dep_fullpath:
@@ -1374,6 +1386,28 @@ def update_pkg_list(
             "--holdver",
         ]
         failure = False
+        if "ccache_dir" in pkg_state[pkg]:
+            pkg_state[pkg]["other_deps"].append("ccache")
+        elif "sccache_dir" in pkg_state[pkg]:
+            pkg_state[pkg]["other_deps"].append("sccache")
+        if len(pkg_state[pkg]["other_deps"]) != 0:
+            prefetch_result = prefetch_dependencies(
+                pkg_state[pkg]["other_deps"], other_state
+            )
+            if prefetch_result != "fetched":
+                log_print(
+                    "ERROR: Failed to prefetch deps {}".format(
+                        pkg_state[pkg]["other_deps"]
+                    ),
+                    other_state=other_state,
+                )
+                failure = True
+                pkg_state[pkg]["build_status"] = "get_dep_fail"
+                break
+            log_print(
+                "Successfully prefetched deps, continuing on to build...",
+                other_state=other_state,
+            )
         for dep in pkg_state[pkg]["other_deps"]:
             dep_fullpath = get_latest_pkg(dep, "/var/cache/pacman/pkg")
             if not dep_fullpath:
@@ -1987,7 +2021,7 @@ fi
     return "ok"
 
 
-def prepare_user_chroot(other_state: [str, Any]):
+def prepare_user_chroot(other_state: dict[str, Any]):
     try:
         log_print(
             'Running "makechrootpkg ... --nobuild" with dummy package to ensure user chroot is ready...',
@@ -2030,6 +2064,24 @@ def prepare_user_chroot(other_state: [str, Any]):
     return True
 
 
+def prefetch_dependencies(pkg_names: [str], other_state: dict[str, Any]):
+    """Returns "fetched" on success."""
+    log_print(
+        f'Prefetching packages "{pkg_names}" with "pacman -Sw"...',
+        other_state=other_state,
+    )
+    command_list = ["/usr/bin/env", "sudo", "pacman", "--noconfirm", "-Sw"]
+    command_list.extend(pkg_names)
+    try:
+        subprocess.run(
+            command_list,
+            check=True,
+        )
+    except subprocess.CalledProcessError:
+        return "fail"
+    return "fetched"
+
+
 def main():
     """The main function."""
     signal.signal(signal.SIGINT, signal_handler)