From b9bc56ca980a6bdae0b16972189ffc34356bfd68 Mon Sep 17 00:00:00 2001
From: aknysh <andriy.knysh@gmail.com>
Date: Thu, 20 Aug 2026 17:56:13 -0400
Subject: [PATCH] fix: guard summary jq against null Entrypoint/Cmd/Env
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The `Docker Inspect` summary step fed `.[0].Config.Entrypoint`,
`.Config.Cmd`, `.Config.Env`, and `.RootFS.Layers` straight into jq's
`join`/`.[]`/`to_entries`, all of which iterate their input. When an
image defines no `ENTRYPOINT` (and/or no `CMD`/`ENV`), those fields are
`null` in `docker inspect`, so jq aborts with:

    jq: error (at inspect.json:NN): Cannot iterate over null (null)

Under the default `bash -e` shell that non-zero exit fails the whole
`Docker Build` step (exit code 5), even though the image built and
pushed fine — it only breaks the post-build job summary.

Every existing test fixture is `FROM nginx`, which inherits a non-null
entrypoint/cmd, so the summary path never hit a null field. Any image
without an entrypoint (e.g. a plain `FROM debian:trixie-slim`) trips it.

Guard each iterating expression with `// []` so null fields render as
empty instead of crashing. Populated images are unaffected.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 action.yml | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/action.yml b/action.yml
index b70d032..4a31896 100644
--- a/action.yml
+++ b/action.yml
@@ -275,8 +275,8 @@ runs:
         SIZE_MB=$(echo "scale=1; $SIZE_BYTES / 1048576" | bc)
         LAYER_COUNT=$(jq   '.[0].RootFS.Layers | length'                        inspect.json)
         PORTS=$(jq -r      '.[0].Config.ExposedPorts // {} | keys | join(", ")' inspect.json)
-        ENTRYPOINT=$(jq -r '.[0].Config.Entrypoint | join(" ")'                 inspect.json)
-        CMD=$(jq -r        '.[0].Config.Cmd | join(" ")'                        inspect.json)
+        ENTRYPOINT=$(jq -r '(.[0].Config.Entrypoint // []) | join(" ")'         inspect.json)
+        CMD=$(jq -r        '(.[0].Config.Cmd // []) | join(" ")'                inspect.json)
         STOP_SIGNAL=$(jq -r '.[0].Config.StopSignal // "n/a"'                   inspect.json)
         DRIVER=$(jq -r     '.[0].GraphDriver.Name'                              inspect.json)
     
@@ -321,7 +321,7 @@ runs:
           echo ""
           echo "| Variable | Value |"
           echo "|---|---|"
-          jq -r '.[0].Config.Env[] | split("=") | "| `\(.[0])` | `\(.[1:] | join("="))` |"' inspect.json
+          jq -r '(.[0].Config.Env // [])[] | split("=") | "| `\(.[0])` | `\(.[1:] | join("="))` |"' inspect.json
           echo ""
           echo "</details>"
           echo ""
@@ -343,7 +343,7 @@ runs:
           echo ""
           echo "| # | Digest |"
           echo "|---|---|"
-          jq -r '.[0].RootFS.Layers | to_entries[] | "| \(.key + 1) | `\(.value)` |"' inspect.json
+          jq -r '(.[0].RootFS.Layers // []) | to_entries[] | "| \(.key + 1) | `\(.value)` |"' inspect.json
           echo ""
           echo "</details>"
           echo ""