the stdout fd contains the build log

Using a pipe enables streaming of logs, which would not be possible with
a regular file output.

6 files changed, 29 insertions, 7 deletions

diff --git a/README.md b/README.md
index 603d157..66b9fa7 100644
--- a/README.md
+++ b/README.md
@@ -23,7 +23,8 @@ The output directory `out` is supposed to be an empty directory. Then run one
 of the backends `mdbp-BACKEND [BACKENDOPTIONS] REQUEST.json`. The process
 blocks until the build has finished and its return code signifies success or
 failure of the operation. Usage of unsupported parameters of the particular
-backend result in a failure of the operation as a whole.
+backend result in a failure of the operation as a whole. The content of the
+stdout file descriptor is to be considered the build log.
 
 When to use mdbp?
 -----------------
diff --git a/TODO.md b/TODO.md
index b24415c..fbcd688 100644
--- a/TODO.md
+++ b/TODO.md
@@ -1,4 +1,3 @@
-* A build log should be supplied in a machine-consumable way.
 * It should be requestable which build artifacts are to be retained.
 * There should be a remote backend performing builds via ssh.
 * There should be a backend supporting a container thingy (e.g. `debspawn`,
diff --git a/mdbp/build_schema.json b/mdbp/build_schema.json
index 138de76..85bcd00 100644
--- a/mdbp/build_schema.json
+++ b/mdbp/build_schema.json
@@ -123,6 +123,11 @@
         "directory": {
           "type": "string",
           "description": "target directory to place output artifacts, can be specified relative to the location of this json file"
+        },
+        "log": {
+          "type": "boolean",
+          "default": true,
+          "description": "whether to output the build log on the stdout file descriptor"
         }
       }
     }
diff --git a/mdbp/mmdebstrap.py b/mdbp/mmdebstrap.py
index 4538067..21862c6 100644
--- a/mdbp/mmdebstrap.py
+++ b/mdbp/mmdebstrap.py
@@ -76,6 +76,7 @@ def main() -> None:
                               "libc-dev:" + hostarch,
                               "libstdc++-dev:" + hostarch))
     buildpath = pathlib.PurePath(build.get("buildpath", "/build/build"))
+    enablelog = build["output"].get("log", True)
 
     with get_dsc(build) as dscpath, \
          tempfile.NamedTemporaryFile("w+") as script:
@@ -91,7 +92,7 @@ def main() -> None:
                         all=["--indep-only"]).get(build.get("type"), []))
         cmd.extend(profile_option(build, "--build-profiles"))
         cmd.append(str(buildpath.parent / dscpath.name))
-        if build.get("bd-uninstallable-explainer") == "apt":
+        if build.get("bd-uninstallable-explainer") == "apt" and enablelog:
             script.write("if ! %s\nthen\n" % priv_drop(cmd, chroot=True))
             cmd[-1:-1] = ['-oDebug::pkgProblemResolver=true',
                           '-oDebug::pkgDepCache::Marker=1',
@@ -132,7 +133,7 @@ def main() -> None:
         pathlib.Path(script.name).chmod(0o755)
         cmd = [
             "mmdebstrap",
-            "--verbose",
+            "--verbose" if enablelog else "--quiet",
             "--mode=unshare",
             "--variant=apt",
             "--architectures=" +
@@ -153,7 +154,11 @@ def main() -> None:
             args.mirror,
         ]
         cmd.extend(build.get("extrarepositories", ()))
-        proc = subprocess.Popen(cmd)
+        proc = subprocess.Popen(cmd,
+                                stdout=None if enablelog
+                                       else subprocess.DEVNULL,
+                                stderr=subprocess.STDOUT if enablelog
+                                       else subprocess.DEVNULL)
         sys.exit(proc.wait())
 
 if __name__ == "__main__":
diff --git a/mdbp/pbuilder.py b/mdbp/pbuilder.py
index 8e2556d..a5f734a 100644
--- a/mdbp/pbuilder.py
+++ b/mdbp/pbuilder.py
@@ -18,6 +18,7 @@ def main() -> None:
     args = parser.parse_args()
     build = args.buildjson
 
+    enablelog = build["output"].get("log", True)
     if build.get("lintian", {}).get("run"):
         raise ValueError("running lintian not supported")
     if "bd-uninstallable-explainer" in build:
@@ -55,9 +56,15 @@ def main() -> None:
                         build.get("type", "binary")])
     cmd.extend(profile_option(build, "--profiles"))
     cmd.extend(["--buildresult", build["output"]["directory"]])
+    if not enablelog:
+        cmd.extend(["--loglevel", "E"])
     with get_dsc(build) as dscpath:
         cmd.append(str(dscpath))
-        proc = subprocess.Popen(cmd, env=compute_env(build))
+        proc = subprocess.Popen(cmd, env=compute_env(build),
+                                stdout=None if enablelog
+                                       else subprocess.DEVNULL,
+                                stderr=subprocess.STDOUT if enablelog
+                                       else subprocess.DEVNULL)
         sys.exit(proc.wait())
 
 if __name__ == "__main__":
diff --git a/mdbp/sbuild.py b/mdbp/sbuild.py
index 6b9c33d..ffaeaf2 100644
--- a/mdbp/sbuild.py
+++ b/mdbp/sbuild.py
@@ -47,7 +47,12 @@ def main() -> None:
     with get_dsc(build) as dscpath:
         cmd.append(str(dscpath.absolute()))
         proc = subprocess.Popen(cmd, env=compute_env(build),
-                                cwd=build["output"]["directory"])
+                                cwd=build["output"]["directory"],
+                                stdout=None if build["output"].get("log", True)
+                                       else subprocess.DEVNULL,
+                                stderr=subprocess.STDOUT
+                                       if build["output"].get("log", True)
+                                       else subprocess.DEVNULL)
         sys.exit(proc.wait())
 
 if __name__ == "__main__":