generator: Simplify error handling

Similar to Rusts return and try, just use exceptions and pretty-print
them at the highest level (instead of presenting the user with a
stacktrace that's harder to read than the error alone).

generator.py

@@ -5,11 +5,6 @@ import argparse
 import subprocess
 import sys
 
-
-NOTHING_TO_BE_DONE = 0
-NEED_UPDATE = 1
-FAILURE = 2
-
 DEFAULT_GIR_FILES_DIRECTORY = Path("./gir-files")
 DEFAULT_GST_GIR_FILES_DIRECTORY = Path("./gst-gir-files")
 DEFAULT_GIR_DIRECTORY = Path("./gir/")
@@ -19,11 +14,7 @@ DEFAULT_GIR_PATH = DEFAULT_GIR_DIRECTORY / "target/release/gir"
 def run_command(command, folder=None):
     if folder is None:
         folder = "."
-    ret = subprocess.run(command, cwd=folder)
+    return subprocess.run(command, cwd=folder, check=True)
-    if ret.returncode != 0:
-        print("Command `{}` failed with `{}`...".format(command, ret))
-        return False
-    return True
 
 
 def spawn_process(command):
@@ -43,37 +34,28 @@ def ask_yes_no_question(question, conf):
     return line.strip().lower() == "y"
 
 
-def def_check_submodule(submodule_path, conf):
+def update_submodule(submodule_path, conf):
     if any(submodule_path.iterdir()):
-        return NOTHING_TO_BE_DONE
+        return False
     print("=> Initializing {} submodule...".format(submodule_path))
-    if not run_command(["git", "submodule", "update", "--init", submodule_path]):
+    run_command(["git", "submodule", "update", "--init", submodule_path])
-        return FAILURE
     print("<= Done!")
 
     if ask_yes_no_question(
         "Do you want to update {} submodule?".format(submodule_path), conf
     ):
         print("=> Updating submodule...")
-        if not run_command(["git", "reset", "--hard", "HEAD"], submodule_path):
+        run_command(["git", "reset", "--hard", "HEAD"], submodule_path)
-            return FAILURE
+        run_command(["git", "pull", "-f", "origin", "master"], submodule_path)
-        if not run_command(["git", "pull", "-f", "origin", "master"], submodule_path):
-            return FAILURE
         print("<= Done!")
-        return NEED_UPDATE
+        return True
-    return NOTHING_TO_BE_DONE
+    return False
 
 
-def build_gir_if_needed(updated_submodule):
+def build_gir():
-    if updated_submodule == FAILURE:
-        return False
     print("=> Building gir...")
-    if update_workspace():
+    update_workspace()
-        print("<= Done!")
+    print("<= Done!")
-    else:
-        print("<= Failed...")
-        return False
-    return True
 
 
 def regen_crates(path, conf):
@@ -97,11 +79,7 @@ def regen_crates(path, conf):
 
             # doc-target-path is relative to `-c`
             path_depth = len(path.parent.parts)
-            doc_path = (
+            doc_path = Path(*[".."] * path_depth, "docs", path.parent, "docs.md")
-                Path(*[".."] * path_depth, "docs")
-                .joinpath(path.parent)
-                .joinpath("docs.md")
-            )
             doc_args = args + [
                 "-m",
                 "doc",
@@ -191,8 +169,8 @@ def main():
     conf = parse_args()
 
     if conf.gir_path == DEFAULT_GIR_PATH:
-        if not build_gir_if_needed(def_check_submodule(DEFAULT_GIR_DIRECTORY, conf)):
+        update_submodule(DEFAULT_GIR_DIRECTORY, conf)
-            return 1
+        build_gir()
 
     print("=> Regenerating crates...")
     for path in conf.path:
@@ -201,10 +179,13 @@ def main():
         for log, p in processes:
             print("==> {}".format(log))
             stdout, stderr = p.communicate()
+            stdout = stdout.decode("utf-8")
+            stderr = stderr.decode("utf-8")
+            assert p.returncode == 0, stderr.strip()
             # Gir doesn't print anything to stdout. If it does, this is likely out of
             # order with stderr, unless the printer/logging flushes in between.
-            assert stdout == b""
+            assert not stdout, "`gir` printed unexpected stdout: {}".format(stdout)
-            print(stderr.decode("utf-8"), end="")
+            print(stderr, end="")
 
     if not conf.no_fmt and not run_command(["cargo", "fmt"]):
         return 1
@@ -214,4 +195,8 @@ def main():
 
 
 if __name__ == "__main__":
-    sys.exit(main())
+    try:
+        main()
+    except Exception as e:
+        print("Error: {}".format(e), file=sys.stderr)
+        sys.exit(1)