add workaround for gitlab ci needs limit (#17219)

* add workaround for gitlab ci needs limit

* fix style/address review comments

* convert filter obj to list

* update command completion

* remove dict comprehension

* add workaround tests

* fix sorting issue between disparate types

* add indeces to format

6 files changed, 236 insertions, 8 deletions

diff --git a/lib/spack/spack/ci.py b/lib/spack/spack/ci.py
index 230f25ccee..580dbf29d2 100644
--- a/lib/spack/spack/ci.py
+++ b/lib/spack/spack/ci.py
@@ -450,7 +450,7 @@ def format_job_needs(phase_name, strip_compilers, dep_jobs,
 
 def generate_gitlab_ci_yaml(env, print_summary, output_file,
                             custom_spack_repo=None, custom_spack_ref=None,
-                            run_optimizer=False):
+                            run_optimizer=False, use_dependencies=False):
     # FIXME: What's the difference between one that opens with 'spack'
     # and one that opens with 'env'?  This will only handle the former.
     with spack.concretize.disable_compiler_existence_check():
@@ -794,6 +794,11 @@ def generate_gitlab_ci_yaml(env, print_summary, output_file,
         import spack.ci_optimization as ci_opt
         sorted_output = ci_opt.optimizer(sorted_output)
 
+    # TODO(opadron): remove this or refactor
+    if use_dependencies:
+        import spack.ci_needs_workaround as cinw
+        sorted_output = cinw.needs_to_dependencies(sorted_output)
+
     with open(output_file, 'w') as outf:
         outf.write(syaml.dump_config(sorted_output, default_flow_style=True))
 
diff --git a/lib/spack/spack/ci_needs_workaround.py b/lib/spack/spack/ci_needs_workaround.py
new file mode 100644
index 0000000000..ba9f7c62af
--- /dev/null
+++ b/lib/spack/spack/ci_needs_workaround.py
@@ -0,0 +1,47 @@
+# Copyright 2013-2020 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+import collections
+
+try:
+    # dynamically import to keep vermin from complaining
+    collections_abc = __import__('collections.abc')
+except ImportError:
+    collections_abc = collections
+
+
+get_job_name = lambda needs_entry: (
+    needs_entry.get('job') if (
+        isinstance(needs_entry, collections_abc.Mapping) and
+        needs_entry.get('artifacts', True))
+
+    else
+
+    needs_entry if isinstance(needs_entry, str)
+
+    else None)
+
+
+def convert_job(job_entry):
+    if not isinstance(job_entry, collections_abc.Mapping):
+        return job_entry
+
+    needs = job_entry.get('needs')
+    if needs is None:
+        return job_entry
+
+    new_job = {}
+    new_job.update(job_entry)
+    del new_job['needs']
+
+    new_job['dependencies'] = list(filter(
+        (lambda x: x is not None),
+        (get_job_name(needs_entry) for needs_entry in needs)))
+
+    return new_job
+
+
+def needs_to_dependencies(yaml):
+    return dict((k, convert_job(v)) for k, v in yaml.items())
diff --git a/lib/spack/spack/ci_optimization.py b/lib/spack/spack/ci_optimization.py
index 693802d06d..d938a681e3 100644
--- a/lib/spack/spack/ci_optimization.py
+++ b/lib/spack/spack/ci_optimization.py
@@ -190,10 +190,10 @@ def print_delta(name, old, new, applied=None):
         applied = (new <= old)
 
     print('\n'.join((
-        '{} {}:',
-        '  before: {: 10d}',
-        '  after : {: 10d}',
-        '  delta : {:+10d} ({:=+3d}.{}%)',
+        '{0} {1}:',
+        '  before: {2: 10d}',
+        '  after : {3: 10d}',
+        '  delta : {4:+10d} ({5:=+3d}.{6}%)',
     )).format(
         name,
         ('+' if applied else 'x'),
diff --git a/lib/spack/spack/cmd/ci.py b/lib/spack/spack/cmd/ci.py
index 3e57c6656a..d42a3e7ae6 100644
--- a/lib/spack/spack/cmd/ci.py
+++ b/lib/spack/spack/cmd/ci.py
@@ -55,10 +55,14 @@ def setup_parser(subparser):
              "should be checked out as a step in each generated job.  " +
              "This argument is ignored if no --spack-repo is provided.")
     generate.add_argument(
-        '--optimize', action='store_true',
+        '--optimize', action='store_true', default=False,
         help="(Experimental) run the generated document through a series of "
              "optimization passes designed to reduce the size of the "
              "generated file.")
+    generate.add_argument(
+        '--dependencies', action='store_true', default=False,
+        help="(Experimental) disable DAG scheduling; use "
+             ' "plain" dependencies.')
     generate.set_defaults(func=ci_generate)
 
     # Check a spec against mirror. Rebuild, create buildcache and push to
@@ -81,6 +85,7 @@ def ci_generate(args):
     spack_repo = args.spack_repo
     spack_ref = args.spack_ref
     run_optimizer = args.optimize
+    use_dependencies = args.dependencies
 
     if not output_file:
         gen_ci_dir = os.getcwd()
@@ -93,7 +98,8 @@ def ci_generate(args):
     # Generate the jobs
     spack_ci.generate_gitlab_ci_yaml(
         env, True, output_file, spack_repo, spack_ref,
-        run_optimizer=run_optimizer)
+        run_optimizer=run_optimizer,
+        use_dependencies=use_dependencies)
 
     if copy_yaml_to:
         copy_to_dir = os.path.dirname(copy_yaml_to)
diff --git a/lib/spack/spack/test/ci.py b/lib/spack/spack/test/ci.py
index a153437ffa..9b3c48654a 100644
--- a/lib/spack/spack/test/ci.py
+++ b/lib/spack/spack/test/ci.py
@@ -15,6 +15,17 @@ import spack.spec as spec
 import spack.util.web as web_util
 import spack.util.gpg
 
+import spack.ci_optimization as ci_opt
+import spack.ci_needs_workaround as cinw
+import spack.util.spack_yaml as syaml
+import itertools as it
+import collections
+try:
+    # dynamically import to keep vermin from complaining
+    collections_abc = __import__('collections.abc')
+except ImportError:
+    collections_abc = collections
+
 
 @pytest.fixture
 def tmp_scope():
@@ -166,3 +177,162 @@ def test_read_write_cdash_ids(config, tmp_scope, tmpdir, mock_packages):
     read_cdashid = ci.read_cdashid_from_mirror(mock_spec, mirror_url)
 
     assert(str(read_cdashid) == orig_cdashid)
+
+
+def test_ci_workarounds():
+    fake_root_spec = 'x' * 544
+    fake_spack_ref = 'x' * 40
+
+    common_variables = {
+        'SPACK_COMPILER_ACTION': 'NONE',
+        'SPACK_IS_PR_PIPELINE': 'False',
+    }
+
+    common_script = ['spack ci rebuild']
+
+    common_before_script = [
+        'git clone "https://github.com/spack/spack"',
+        ' && '.join((
+            'pushd ./spack',
+            'git checkout "{ref}"'.format(ref=fake_spack_ref),
+            'popd')),
+        '. "./spack/share/spack/setup-env.sh"'
+    ]
+
+    def make_build_job(name, deps, stage, use_artifact_buildcache, optimize,
+                       use_dependencies):
+        variables = common_variables.copy()
+        variables['SPACK_JOB_SPEC_PKG_NAME'] = name
+
+        result = {
+            'stage': stage,
+            'tags': ['tag-0', 'tag-1'],
+            'artifacts': {
+                'paths': [
+                    'jobs_scratch_dir',
+                    'cdash_report',
+                    name + '.spec.yaml',
+                    name + '.cdashid',
+                    name
+                ],
+                'when': 'always'
+            },
+            'retry': {'max': 2, 'when': ['always']},
+            'after_script': ['rm -rf "./spack"'],
+            'image': {'name': 'spack/centos7', 'entrypoint': ['']},
+        }
+
+        if optimize:
+            result['extends'] = ['.c0', '.c1', '.c2']
+        else:
+            variables['SPACK_ROOT_SPEC'] = fake_root_spec
+            result['script'] = common_script
+            result['before_script'] = common_before_script
+
+        result['variables'] = variables
+
+        if use_dependencies:
+            result['dependencies'] = (
+                list(deps) if use_artifact_buildcache
+                else [])
+        else:
+            result['needs'] = [
+                {'job': dep, 'artifacts': use_artifact_buildcache}
+                for dep in deps]
+
+        return {name: result}
+
+    def make_rebuild_index_job(
+            use_artifact_buildcache, optimize, use_dependencies):
+
+        result = {
+            'stage': 'stage-rebuild-index',
+            'script': 'spack buildcache update-index -d s3://mirror',
+            'tags': ['tag-0', 'tag-1'],
+            'image': {'name': 'spack/centos7', 'entrypoint': ['']},
+            'after_script': ['rm -rf "./spack"'],
+        }
+
+        if optimize:
+            result['extends'] = '.c1'
+        else:
+            result['before_script'] = common_before_script
+
+        return {'rebuild-index': result}
+
+    def make_factored_jobs(optimize):
+        return {
+            '.c0': {'script': common_script},
+            '.c1': {'before_script': common_before_script},
+            '.c2': {'variables': {'SPACK_ROOT_SPEC': fake_root_spec}}
+        } if optimize else {}
+
+    def make_yaml_obj(use_artifact_buildcache, optimize, use_dependencies):
+        result = {}
+
+        result.update(make_build_job(
+            'pkg-a', [], 'stage-0', use_artifact_buildcache, optimize,
+            use_dependencies))
+
+        result.update(make_build_job(
+            'pkg-b', ['pkg-a'], 'stage-1', use_artifact_buildcache, optimize,
+            use_dependencies))
+
+        result.update(make_build_job(
+            'pkg-c', ['pkg-a', 'pkg-b'], 'stage-2', use_artifact_buildcache,
+            optimize, use_dependencies))
+
+        result.update(make_rebuild_index_job(
+            use_artifact_buildcache, optimize, use_dependencies))
+
+        result.update(make_factored_jobs(optimize))
+
+        return result
+
+    def sort_yaml_obj(obj):
+        if isinstance(obj, collections_abc.Mapping):
+            result = syaml.syaml_dict()
+            for k in sorted(obj.keys(), key=str):
+                result[k] = sort_yaml_obj(obj[k])
+            return result
+
+        if (isinstance(obj, collections_abc.Sequence) and
+                not isinstance(obj, str)):
+            return syaml.syaml_list(sorted(
+                (sort_yaml_obj(x) for x in obj), key=str))
+
+        return obj
+
+    # test every combination of:
+    #     use artifact buildcache: true or false
+    #     run optimization pass: true or false
+    #     convert needs to dependencies: true or false
+    for use_ab in (False, True):
+        original = make_yaml_obj(
+            use_artifact_buildcache=use_ab,
+            optimize=False,
+            use_dependencies=False)
+
+        for opt, deps in it.product(*(((False, True),) * 2)):
+            # neither optimizing nor converting needs->dependencies
+            if not (opt or deps):
+                # therefore, nothing to test
+                continue
+
+            predicted = make_yaml_obj(
+                use_artifact_buildcache=use_ab,
+                optimize=opt,
+                use_dependencies=deps)
+
+            actual = original.copy()
+            if opt:
+                actual = ci_opt.optimizer(actual)
+            if deps:
+                actual = cinw.needs_to_dependencies(actual)
+
+            predicted = syaml.dump_config(
+                sort_yaml_obj(predicted), default_flow_style=True)
+            actual = syaml.dump_config(
+                sort_yaml_obj(actual), default_flow_style=True)
+
+            assert(predicted == actual)
diff --git a/share/spack/spack-completion.bash b/share/spack/spack-completion.bash
index ffd7596416..eff9e15b2c 100755
--- a/share/spack/spack-completion.bash
+++ b/share/spack/spack-completion.bash
@@ -474,7 +474,7 @@ _spack_ci() {
 }
 
 _spack_ci_generate() {
-    SPACK_COMPREPLY="-h --help --output-file --copy-to --spack-repo --spack-ref --optimize"
+    SPACK_COMPREPLY="-h --help --output-file --copy-to --spack-repo --spack-ref --optimize --dependencies"
 }
 
 _spack_ci_rebuild() {