Implement allowed-skips input

This change lets the end-users mark certain jobs as allowed to be non-
voting when skipped only but their failures will affect the outcome.

Resolves #1

README.md

@@ -78,17 +78,21 @@ jobs:
       uses: re-actors/alls-green@release/v1
       with:
         allowed-failures: docs, linters
+        allowed-skips: non-voting-flaky-job
         jobs: ${{ toJSON(needs) }}
 ...
 ```
 
 
 ## Options
 
-There are two options — `allowed-failures` and `jobs`. The former is
-optional but the later is mandatory. `allowed-failures` tells the action
-which jobs should not affect the outcome, by default all the jobs will
-be "voting". `jobs` is an object representing the jobs that should
+There are three options — `allowed-failures`, `allowed-skips` and
+`jobs`. The first two are optional but `jobs` is mandatory.
+`allowed-failures` tells the action which jobs should not affect the
+outcome if they don't succeed, by default all the jobs will
+be "voting". Same goes for `allowed-skips` — it won't allow the listed
+jobs to affect the outcome if they are skipped but are still "voting" in
+case they run. `jobs` is an object representing the jobs that should
 affect the decision of whether the pipeline failed or not, it is
 important to pass a JSON-serialized `needs` context to this argument.
 

action.yml

@@ -23,6 +23,13 @@ inputs:
       Job names that are allowed to fail and not affect the outcome,
       as a comma-separated list or serialized as a JSON string
     required: false
+  allowed-skips:
+    default: >-
+      []
+    description: >-
+      Job names that are allowed to be skipped and not affect the
+      outcome, as a comma-separated list or serialized as a JSON string
+    required: false
 
 outputs:
   failure:
@@ -48,6 +55,10 @@ runs:
         ${{ inputs.allowed-failures }}
       EOM
       )" \
+      "$(cat << EOM
+        ${{ inputs.allowed-skips }}
+      EOM
+      )" \
       "$(cat << EOM
         ${{ inputs.jobs }}
       EOM

src/normalize_needed_jobs_status.py

@@ -35,21 +35,24 @@ def parse_as_list(input_text):
         return [s.strip() for s in input_text.split(',')]
 
 
-def parse_inputs(raw_allowed_failures, raw_jobs):
+def parse_inputs(raw_allowed_failures, raw_allowed_skips, raw_jobs):
     """Normalize the action inputs by turning them into data."""
     allowed_failures_input = parse_as_list(raw_allowed_failures)
-
+    allowed_skips_input = parse_as_list(raw_allowed_skips)
 
     return {
         'allowed_failures': allowed_failures_input,
+        'allowed_skips': allowed_skips_input,
         'jobs': json.loads(raw_jobs),
     }
 
 
 def log_decision_details(
         job_matrix_succeeded,
         jobs_allowed_to_fail,
+        jobs_allowed_to_be_skipped,
         allowed_to_fail_jobs_succeeded,
+        allowed_to_be_skipped_jobs_succeeded,
         jobs,
 ):
     """Record the decisions made into console output."""
@@ -73,27 +76,46 @@ def log_decision_details(
         )
 
 
+    if jobs_allowed_to_be_skipped and allowed_to_be_skipped_jobs_succeeded:
+        print_to_stderr(
+            '🛈 All of the allowed to be skipped dependency jobs succeeded.',
+        )
+    elif jobs_allowed_to_fail:
+        print_to_stderr(
+            '🛈 Some of the allowed to be skipped jobs did not succeed.',
+        )
+
+
     print_to_stderr('📝 Job statuses:')
     for name, job in jobs.items():
         print_to_stderr(
             '📝 {name} → {emoji} {result} [{status}]'.
             format(
-                emoji='✓' if job['result'] == 'success' else '❌',
+                emoji='✓' if job['result'] == 'success'
+                else '❌' if job['result'] == 'failure'
+                else '⬜',
                 name=name,
                 result=job['result'],
                 status='allowed to fail' if name in jobs_allowed_to_fail
-                else 'required to succeed',
+                else 'required to succeed'
+                if name not in jobs_allowed_to_be_skipped
+                else 'required to succeed or be skipped',
             ),
         )
 
 
 def main(argv):
     """Decide whether the needed jobs got satisfactory results."""
-    inputs = parse_inputs(raw_allowed_failures=argv[1], raw_jobs=argv[2])
+    inputs = parse_inputs(
+        raw_allowed_failures=argv[1],
+        raw_allowed_skips=argv[2],
+        raw_jobs=argv[3],
+    )
 
 
     jobs = inputs['jobs'] or {}
-    jobs_allowed_to_fail = inputs['allowed_failures'] or []
+    jobs_allowed_to_fail = set(inputs['allowed_failures'] or [])
+    jobs_allowed_to_be_skipped = set(inputs['allowed_skips'] or [])
 
     if not jobs:
         sys.exit(
@@ -104,7 +126,10 @@ def main(argv):
 
     job_matrix_succeeded = all(
         job['result'] == 'success' for name, job in jobs.items()
-        if name not in jobs_allowed_to_fail
+        if name not in (jobs_allowed_to_fail | jobs_allowed_to_be_skipped)
+    ) and all(
+        job['result'] in {'skipped', 'success'} for name, job in jobs.items()
+        if name in jobs_allowed_to_be_skipped
     )
     set_final_result_outputs(job_matrix_succeeded)
 
@@ -115,10 +140,18 @@ def main(argv):
     )
 
 
+    allowed_to_be_skipped_jobs_succeeded = all(
+        job['result'] == 'success' for name, job in jobs.items()
+        if name in jobs_allowed_to_be_skipped
+    )
+
+
     log_decision_details(
             job_matrix_succeeded,
             jobs_allowed_to_fail,
+            jobs_allowed_to_be_skipped,
             allowed_to_fail_jobs_succeeded,
+            allowed_to_be_skipped_jobs_succeeded,
             jobs,
     )