Add YAML validation for SKILL.md frontmatter and fix JSON check - #9
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`gh skill install` refused the map skill outright on main:
failed to install skill "map": could not inject metadata:
invalid frontmatter YAML: yaml: line 2: mapping values are not
allowed in this context
and left an empty ~/.copilot/skills/map/ behind, so `gh skill list`
reported a skill with no content.
The cause is one character. A plain (unquoted) YAML scalar cannot
contain ": " - the parser reads it as a nested mapping - and map's
description had one buried mid-sentence: "One verb for both: no
reference yet means build it". Now an em-dash. Every other skill
passes because none of them happen to contain a colon-space.
This shipped: the flagship command could not be installed via the
GitHub CLI at all, on the release that introduced it.
Nothing here could have caught it. Check 3 reads `name:` out of the
frontmatter with sed and never asks whether the block is YAML, and
sed does not care. Check 12m now parses every SKILL.md frontmatter
with a real YAML parser (ruby's psych, python's yaml as fallback, a
targeted ": " scan if neither is present) and asserts name and
description survive the parse. Negative-tested by reintroducing the
colon.
Also, a smaller misdiagnosis in check 9: `git ls-files` still lists a
tracked file deleted from the worktree, so a pending deletion was
reported as "invalid JSON: <path>", sending the reader hunting for a
stray comma in a file that is not there. Missing files are now
skipped.
Drops .claude/settings.json, which only enabled the capstone plugin
for this project and follows the plugin having been uninstalled.
Reviewer's GuideThe PR strengthens lint-sync by adding SKILL.md frontmatter YAML validation with Ruby/Python/regex fallbacks, avoids false JSON errors for tracked deletions, and fixes the map skill metadata plus obsolete Claude configuration. Flow diagram for lint-sync validation checksflowchart TD
Start["lint-sync.sh"] --> JSON["Validate tracked JSON files"]
JSON --> Exists{"File exists in worktree?"}
Exists -->|No| Skip["Skip pending deletion"]
Exists -->|Yes| ParseJSON["python3 json.load"]
Skip --> Frontmatter["Validate SKILL.md frontmatter"]
ParseJSON --> Frontmatter
Frontmatter --> Ruby{"ruby available?"}
Ruby -->|Yes| RubyYAML["YAML.safe_load"]
Ruby -->|No| PyYAML{"python3 yaml available?"}
PyYAML -->|Yes| PythonYAML["yaml.safe_load"]
PyYAML -->|No| Regex["Scan for plain scalar : trap"]
RubyYAML --> Result["Report validation error if invalid"]
PythonYAML --> Result
Regex --> Result
File-Level Changes
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Hey - I've found 4 issues
Prompt for AI Agents
Please address the comments from this code review:
## Individual Comments
### Comment 1
<location path="skills/core/scripts/lint-sync.sh" line_range="512" />
<code_context>
+# check here still passes. Prefer ruby (macOS ships psych); fall
+# back to python's yaml, then to a targeted scan for the traps.
+for f in skills/*/SKILL.md; do
+ fm=$(sed -n '/^---$/,/^---$/p' "$f" | sed '1d;$d')
+ if command -v ruby >/dev/null 2>&1; then
+ printf '%s\n' "$fm" | ruby -ryaml -e 'YAML.safe_load(STDIN.read)' >/dev/null 2>&1 \
</code_context>
<issue_to_address>
**issue (bug_risk):** The extraction does not verify that each SKILL.md has both opening and closing `---` delimiters. When the closing delimiter is missing, `sed` consumes the rest of the file and removes only the first and last lines, so a file whose remaining content is blank or comments can pass YAML validation despite having malformed frontmatter.
**Triggers:** When a SKILL.md is missing its closing frontmatter delimiter and the remaining body is YAML-compatible.
**Suggested fix:** Check that exactly two delimiter lines are present and fail before parsing when either delimiter is missing or the delimiters are not in the expected positions.
</issue_to_address>
### Comment 2
<location path="skills/core/scripts/lint-sync.sh" line_range="514-519" />
<code_context>
+for f in skills/*/SKILL.md; do
+ fm=$(sed -n '/^---$/,/^---$/p' "$f" | sed '1d;$d')
+ if command -v ruby >/dev/null 2>&1; then
+ printf '%s\n' "$fm" | ruby -ryaml -e 'YAML.safe_load(STDIN.read)' >/dev/null 2>&1 \
+ || err "$f frontmatter is not valid YAML"
+ elif command -v python3 >/dev/null 2>&1 \
+ && python3 -c 'import yaml' >/dev/null 2>&1; then
+ printf '%s\n' "$fm" | python3 -c 'import yaml,sys; yaml.safe_load(sys.stdin)' >/dev/null 2>&1 \
+ || err "$f frontmatter is not valid YAML"
+ else
</code_context>
<issue_to_address>
**issue (bug_risk):** The new check only tests whether the extracted block parses as YAML; it never verifies that required `name` and `description` keys survive the parse. A SKILL.md with valid YAML frontmatter containing only unrelated keys therefore passes check 12m, contrary to the stated requirement that name and description be asserted.
**Triggers:** When a skill has syntactically valid frontmatter but omits `description` (or otherwise omits required metadata).
**Suggested fix:** Capture the parsed mapping and explicitly require non-null `name` and `description` values, while preserving the existing directory-name check for `name`.
```suggestion
printf '%s\n' "$fm" | ruby -ryaml -e 'm = YAML.safe_load(STDIN.read); abort unless m.is_a?(Hash) && !m["name"].nil? && !m["description"].nil?' >/dev/null 2>&1 \
|| err "$f frontmatter is not valid YAML"
elif command -v python3 >/dev/null 2>&1 \
&& python3 -c 'import yaml' >/dev/null 2>&1; then
printf '%s\n' "$fm" | python3 -c 'import yaml,sys; m=yaml.safe_load(sys.stdin); sys.exit(0 if isinstance(m,dict) and m.get("name") is not None and m.get("description") is not None else 1)' >/dev/null 2>&1 \
|| err "$f frontmatter is not valid YAML"
```
</issue_to_address>
### Comment 3
<location path="skills/core/scripts/lint-sync.sh" line_range="513" />
<code_context>
+# back to python's yaml, then to a targeted scan for the traps.
+for f in skills/*/SKILL.md; do
+ fm=$(sed -n '/^---$/,/^---$/p' "$f" | sed '1d;$d')
+ if command -v ruby >/dev/null 2>&1; then
+ printf '%s\n' "$fm" | ruby -ryaml -e 'YAML.safe_load(STDIN.read)' >/dev/null 2>&1 \
+ || err "$f frontmatter is not valid YAML"
+ elif command -v python3 >/dev/null 2>&1 \
</code_context>
<issue_to_address>
**issue (bug_risk):** The availability test selects Ruby solely from `command -v ruby`; if Ruby is installed without its YAML/Psych library, `ruby -ryaml` fails for every file and the script reports invalid YAML instead of trying the available Python YAML fallback.
**Triggers:** When `ruby` is installed but the `yaml`/Psych library is unavailable and Python with PyYAML is installed.
**Suggested fix:** Probe `ruby -ryaml -e ...` before selecting the Ruby branch, or fall through to the Python branch when the Ruby parser invocation cannot load.
```suggestion
if command -v ruby >/dev/null 2>&1 \
&& ruby -ryaml -e 'exit' >/dev/null 2>&1; then
```
</issue_to_address>
### Comment 4
<location path="skills/core/scripts/lint-sync.sh" line_range="521-522" />
<code_context>
+ printf '%s\n' "$fm" | python3 -c 'import yaml,sys; yaml.safe_load(sys.stdin)' >/dev/null 2>&1 \
+ || err "$f frontmatter is not valid YAML"
+ else
+ printf '%s\n' "$fm" | grep -q ': .*: ' \
+ && err "$f frontmatter has a plain scalar containing \": \" (breaks YAML)"
+ fi
+done
</code_context>
<issue_to_address>
**issue (bug_risk):** The parser-free fallback flags any line matching `: .*: `, including valid quoted YAML such as `description: "Use foo: bar"`; with neither Ruby nor PyYAML available, valid frontmatter is reported as invalid solely because the quoted scalar contains colon-space.
**Triggers:** When the host has neither a usable Ruby YAML parser nor Python's yaml module and a description contains `: ` inside quotes.
**Suggested fix:** Make the fallback distinguish quoted scalars from unquoted plain scalars, or report that YAML validation is unavailable instead of rejecting valid quoted YAML.
```suggestion
err "$f frontmatter YAML validation unavailable (install ruby or python3 with PyYAML)"
```
</issue_to_address>Sourcery assessment
Approval pending. 4 findings to address first.
Blocking findings: skills/core/scripts/lint-sync.sh:512, skills/core/scripts/lint-sync.sh:519, skills/core/scripts/lint-sync.sh:513, skills/core/scripts/lint-sync.sh:522
Help me be more useful! Please click 👍 or 👎 on each comment and I'll use the feedback to improve your reviews.
| # check here still passes. Prefer ruby (macOS ships psych); fall | ||
| # back to python's yaml, then to a targeted scan for the traps. | ||
| for f in skills/*/SKILL.md; do | ||
| fm=$(sed -n '/^---$/,/^---$/p' "$f" | sed '1d;$d') |
There was a problem hiding this comment.
issue (bug_risk): The extraction does not verify that each SKILL.md has both opening and closing --- delimiters. When the closing delimiter is missing, sed consumes the rest of the file and removes only the first and last lines, so a file whose remaining content is blank or comments can pass YAML validation despite having malformed frontmatter.
Triggers: When a SKILL.md is missing its closing frontmatter delimiter and the remaining body is YAML-compatible.
Suggested fix: Check that exactly two delimiter lines are present and fail before parsing when either delimiter is missing or the delimiters are not in the expected positions.
Comment on lines
+514
to
+519
| printf '%s\n' "$fm" | ruby -ryaml -e 'YAML.safe_load(STDIN.read)' >/dev/null 2>&1 \ | ||
| || err "$f frontmatter is not valid YAML" | ||
| elif command -v python3 >/dev/null 2>&1 \ | ||
| && python3 -c 'import yaml' >/dev/null 2>&1; then | ||
| printf '%s\n' "$fm" | python3 -c 'import yaml,sys; yaml.safe_load(sys.stdin)' >/dev/null 2>&1 \ | ||
| || err "$f frontmatter is not valid YAML" |
There was a problem hiding this comment.
issue (bug_risk): The new check only tests whether the extracted block parses as YAML; it never verifies that required name and description keys survive the parse. A SKILL.md with valid YAML frontmatter containing only unrelated keys therefore passes check 12m, contrary to the stated requirement that name and description be asserted.
Triggers: When a skill has syntactically valid frontmatter but omits description (or otherwise omits required metadata).
Suggested fix: Capture the parsed mapping and explicitly require non-null name and description values, while preserving the existing directory-name check for name.
Suggested change
| printf '%s\n' "$fm" | ruby -ryaml -e 'YAML.safe_load(STDIN.read)' >/dev/null 2>&1 \ | |
| || err "$f frontmatter is not valid YAML" | |
| elif command -v python3 >/dev/null 2>&1 \ | |
| && python3 -c 'import yaml' >/dev/null 2>&1; then | |
| printf '%s\n' "$fm" | python3 -c 'import yaml,sys; yaml.safe_load(sys.stdin)' >/dev/null 2>&1 \ | |
| || err "$f frontmatter is not valid YAML" | |
| printf '%s\n' "$fm" | ruby -ryaml -e 'm = YAML.safe_load(STDIN.read); abort unless m.is_a?(Hash) && !m["name"].nil? && !m["description"].nil?' >/dev/null 2>&1 \ | |
| || err "$f frontmatter is not valid YAML" | |
| elif command -v python3 >/dev/null 2>&1 \ | |
| && python3 -c 'import yaml' >/dev/null 2>&1; then | |
| printf '%s\n' "$fm" | python3 -c 'import yaml,sys; m=yaml.safe_load(sys.stdin); sys.exit(0 if isinstance(m,dict) and m.get("name") is not None and m.get("description") is not None else 1)' >/dev/null 2>&1 \ | |
| || err "$f frontmatter is not valid YAML" |
| # back to python's yaml, then to a targeted scan for the traps. | ||
| for f in skills/*/SKILL.md; do | ||
| fm=$(sed -n '/^---$/,/^---$/p' "$f" | sed '1d;$d') | ||
| if command -v ruby >/dev/null 2>&1; then |
There was a problem hiding this comment.
issue (bug_risk): The availability test selects Ruby solely from command -v ruby; if Ruby is installed without its YAML/Psych library, ruby -ryaml fails for every file and the script reports invalid YAML instead of trying the available Python YAML fallback.
Triggers: When ruby is installed but the yaml/Psych library is unavailable and Python with PyYAML is installed.
Suggested fix: Probe ruby -ryaml -e ... before selecting the Ruby branch, or fall through to the Python branch when the Ruby parser invocation cannot load.
Suggested change
| if command -v ruby >/dev/null 2>&1; then | |
| if command -v ruby >/dev/null 2>&1 \ | |
| && ruby -ryaml -e 'exit' >/dev/null 2>&1; then |
Comment on lines
+521
to
+522
| printf '%s\n' "$fm" | grep -q ': .*: ' \ | ||
| && err "$f frontmatter has a plain scalar containing \": \" (breaks YAML)" |
There was a problem hiding this comment.
issue (bug_risk): The parser-free fallback flags any line matching : .*: , including valid quoted YAML such as description: "Use foo: bar"; with neither Ruby nor PyYAML available, valid frontmatter is reported as invalid solely because the quoted scalar contains colon-space.
Triggers: When the host has neither a usable Ruby YAML parser nor Python's yaml module and a description contains : inside quotes.
Suggested fix: Make the fallback distinguish quoted scalars from unquoted plain scalars, or report that YAML validation is unavailable instead of rejecting valid quoted YAML.
Suggested change
| printf '%s\n' "$fm" | grep -q ': .*: ' \ | |
| && err "$f frontmatter has a plain scalar containing \": \" (breaks YAML)" | |
| err "$f frontmatter YAML validation unavailable (install ruby or python3 with PyYAML)" |
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Summary
This PR improves the lint-sync validation script by adding YAML frontmatter validation for SKILL.md files and fixing a false positive in JSON validation for deleted files.
Key Changes
skills/map/SKILL.mdto use an em dash instead of a colon in the description to avoid YAML parsing issues with plain scalars containing ": ".claude/settings.jsonconfiguration fileImplementation Details
The YAML validation check extracts frontmatter between
---delimiters and validates it using available tools in order of preference:This addresses a real issue where invalid frontmatter YAML would cause
gh skill installto fail with an empty directory left behind, while existing grep-based checks would still pass.https://claude.ai/code/session_01BPKdCvDCZzUuTmNTXRhRH6
Summary by Sourcery
Strengthen skill metadata validation by checking YAML frontmatter and handling deleted JSON files correctly.
New Features:
Bug Fixes:
Chores: