Addition of --out option to bst artifact log:becky/artifact_log_file_option

A --out option has been added, allowing an artifact log to be
written to a logfile. This is particularly useful when more
than one artifact's log is wanting to be read; It will write
a file for each log.
A test and NEWS entry have also been added.

3 files changed, 71 insertions, 13 deletions

diff --git a/src/buildstream/_frontend/cli.py b/src/buildstream/_frontend/cli.py
index 661e39575..c1b06b2d1 100644
--- a/src/buildstream/_frontend/cli.py
+++ b/src/buildstream/_frontend/cli.py
@@ -4,6 +4,7 @@ import sys
 from functools import partial
 import fcntl
 
+import shutil
 import click
 from .. import _yaml
 from .._exceptions import BstError, LoadError, AppError
@@ -1219,19 +1220,45 @@ def artifact_push(app, elements, deps, remote):
 #                     Artifact Log Command                     #
 ################################################################
 @artifact.command(name='log', short_help="Show logs of artifacts")
+@click.option('--out',
+              type=click.Path(file_okay=True, writable=True),
+              help="Output logs to individual files in the specified path. If absent, logs are written to stdout.")
 @click.argument('artifacts', type=click.Path(), nargs=-1)
 @click.pass_obj
-def artifact_log(app, artifacts):
+def artifact_log(app, artifacts, out):
     """Show build logs of artifacts"""
-
     with app.initialized():
-        log_file_paths = app.stream.artifact_log(artifacts)
-
-        for log in log_file_paths:
-            with open(log) as f:
-                data = f.read()
+        artifact_logs = app.stream.artifact_log(artifacts)
+
+        if not out:
+            try:
+                for log in list(artifact_logs.values()):
+                    with open(log[0], 'r') as f:
+                        data = f.read()
+                    click.echo_via_pager(data)
+            except (OSError, FileNotFoundError):
+                click.echo("Error: file cannot be opened", err=True)
+                sys.exit(1)
 
-            click.echo_via_pager(data)
+        else:
+            try:
+                os.mkdir(out)
+            except FileExistsError:
+                click.echo("Error: {} already exists".format(out), err=True)
+                sys.exit(1)
+
+            for name, log_files in artifact_logs.items():
+                if len(log_files) > 1:
+                    os.mkdir(name)
+                    for log in log_files:
+                        dest = os.path.join(out, name, log)
+                        shutil.copy(log, dest)
+                    # make a dir and write in log files
+                else:
+                    log_name = os.path.splitext(name)[0] + '.log'
+                    dest = os.path.join(out, log_name)
+                    shutil.copy(log_files[0], dest)
+                    # write a log file
 
 
 ################################################################
diff --git a/src/buildstream/_stream.py b/src/buildstream/_stream.py
index 554debaae..95b306b47 100644
--- a/src/buildstream/_stream.py
+++ b/src/buildstream/_stream.py
@@ -648,7 +648,7 @@ class Stream():
         # Return list of Element and/or ArtifactElement objects
         target_objects = self.load_selection(targets, selection=PipelineSelection.NONE, load_refs=True)
 
-        log_file_paths = []
+        artifact_logs = {}
         for obj in target_objects:
             ref = obj.get_artifact_name()
             if not obj._cached():
@@ -658,9 +658,9 @@ class Stream():
                 self._message(MessageType.WARN, "{} is cached without log files".format(ref))
                 continue
 
-            log_file_paths.extend(obj.get_logs())
+            artifact_logs[obj.name] = obj.get_logs()
 
-        return log_file_paths
+        return artifact_logs
 
     # artifact_list_contents()
     #
diff --git a/tests/frontend/artifact.py b/tests/frontend/artifact.py
index cbc9ab022..9ad03909e 100644
--- a/tests/frontend/artifact.py
+++ b/tests/frontend/artifact.py
@@ -69,8 +69,7 @@ def test_artifact_log(cli, datafiles):
     # Read the log via glob
     result = cli.run(project=project, args=['artifact', 'log', 'test/target/*'])
     assert result.exit_code == 0
-    # The artifact is cached under both a strong key and a weak key
-    assert (log + log) == result.output
+    assert log == result.output
 
 
 @pytest.mark.datafiles(DATA_DIR)
@@ -140,6 +139,38 @@ def test_artifact_list_exact_contents_glob(cli, datafiles):
         assert artifact in result.output
 
 
+@pytest.mark.datafiles(DATA_DIR)
+def test_artifact_log_files(cli, datafiles):
+    project = str(datafiles)
+
+    # Ensure we have an artifact to read
+    result = cli.run(project=project, args=['build', 'target.bst'])
+    assert result.exit_code == 0
+
+    logfiles = os.path.join(project, "logfiles")
+    target = os.path.join(project, logfiles, "target.log")
+    import_bin = os.path.join(project, logfiles, "import-bin.log")
+    # Ensure the logfile doesn't exist before the command is run
+    assert not os.path.exists(logfiles)
+    assert not os.path.exists(target)
+    assert not os.path.exists(import_bin)
+
+    # Run the command and ensure the file now exists
+    result = cli.run(project=project, args=['artifact', 'log', '--out', logfiles, 'target.bst', 'import-bin.bst'])
+    assert result.exit_code == 0
+    assert os.path.exists(logfiles)
+    assert os.path.exists(target)
+    assert os.path.exists(import_bin)
+
+    # Ensure the file contains the logs by checking for the LOG line
+    with open(target, 'r') as f:
+        data = f.read()
+        assert "LOG     target.bst" in data
+    with open(import_bin, 'r') as f:
+        data = f.read()
+        assert "LOG     import-bin.bst" in data
+
+
 # Test that we can delete the artifact of the element which corresponds
 # to the current project state
 @pytest.mark.datafiles(DATA_DIR)