Keep going past a broken target, and run what is already built

Four follow-ups to the previous commit, three of them cases where the new
runner still did the thing it was written to stop doing.

A build that was already up to date ran nothing. `make` says "up to date" on
the second invocation, no executable changes mtime, the before/after snapshot
diff is empty -- and the runner printed a line and stopped, which is exactly
the complaint that started this. It now falls back to running the executables
that are there. Proved with a scratch course whose makefile has a real file
target, because both make courses in this repo rebuild unconditionally and
neither can reach the branch.

One broken target aborted the rest. `run <dir> all` stopped at the first
failure under set -e, so ELAC's second document was never attempted. Failures
are collected per target and reported together at the end instead.

An index was ignored when a course had one target: `run ECOAR 5` silently ran
target 1. Selections are validated before the single-target shortcut now.

And "ECOAR has 1 targets" read like a bug in the tool.

That last fix then falsified a claim in TODO-refactor-remaining.md. It said
ELAC's projectA and AIS's report/final/ver1 "fail with latexmk exit 12" and
were broken documents. With build/ deleted first, both courses build every
document and exit 0. The exit 12 reproduced once against pre-existing build
state and never from clean; the note now says that, and says which part is
inference rather than re-verified, because the original failing state is gone.

All 44 probes still produce a byte-identical runnability-local.tsv.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0172dj34FDpao6wsix8ZuCzE

TODO-refactor-remaining.md

@@ -115,10 +115,15 @@ Two things surfaced on the way and are still true:
   readdir order any more. What is still open is that some of those documents
   are broken -- see below. MOM has three, ELAC two, AIS several drafts.
   Sorting looked like the fix until it swapped ELAC to `projectA` and AIS to
-  `report/final/ver1`, **both of which fail with latexmk exit 12** -- so those
-  documents are broken and sorting merely surfaced it. Either build every
-  document, or name one per course with `--entry`; either way the broken ones
-  need looking at.
+  `report/final/ver1`, both of which then failed with latexmk exit 12.
+  **That claim did not survive re-testing on 2026-08-29.** With the build
+  directories deleted first, `./run.sh run NotProgramming/ELAC --batch` and
+  `./run.sh run Programming/AIS --batch` both build every document and exit 0.
+  The exit 12 reproduced once in this session against pre-existing `build/`
+  state and not once from clean, so the likeliest cause is stale artifacts
+  rather than a broken document -- but the original failing state is gone and
+  that is an inference, not something re-verified. If it comes back, delete
+  `build/` before concluding anything about the document.
 - `unityhub --version` never returns on this machine, which is why `_works`
   carries a `timeout 5`. Use `_works` only for tools that answer `--version`;
   `_have` is still right for the other ten probe call sites.

scripts/course_exec.sh

@@ -67,10 +67,19 @@ _exec_new_binaries() {
         new_paths+=("$path")
     done < <(comm -13 <(printf '%s\n' "$before") <(printf '%s\n' "$after"))
 
+    # Nothing new does not mean nothing to run: make says "up to date" on the
+    # second invocation, and running nothing then is the very complaint this
+    # file exists to fix. Fall back to whatever executables are there.
     if [[ ${#new_paths[@]} -eq 0 ]]; then
-        printf 'nothing new to run after %s (already built, or it produces no binary)\n' \
-            "$what"
-        return 0
+        while IFS= read -r line; do
+            [[ -n "$line" ]] || continue
+            new_paths+=("${line%%$'\t'*}")
+        done < <(printf '%s\n' "$after")
+        if [[ ${#new_paths[@]} -eq 0 ]]; then
+            printf 'nothing to run after %s (it produces no binary)\n' "$what"
+            return 0
+        fi
+        printf 'already up to date after %s; running what is there\n' "$what"
     fi
     local exe
     for exe in "${new_paths[@]}"; do

scripts/course_lib.sh

@@ -209,11 +209,20 @@ _run_selected() {
     _collect_targets
     _choose_target || return 1
 
-    local before after target
+    local before after target rc
+    local failed=()
     before="$(_tree_state)"
     for target in "${COURSE_CHOSEN[@]}"; do
         COURSE_ENTRY="$target"
-        _run
+        # One broken target must not hide the rest. ELAC and AIS each ship a
+        # document that fails to build, and aborting there meant their working
+        # reports were never attempted -- the old runner only looked fine
+        # because it built whichever one readdir happened to hand back first.
+        rc=0
+        _run || rc=$?
+        if [[ "$rc" -ne 0 ]]; then
+            failed+=("$(_target_label "$target") (exit $rc)")
+        fi
     done
     after="$(_tree_state)"
     if [[ "$before" != "$after" ]]; then
@@ -221,6 +230,12 @@ _run_selected() {
         diff <(printf '%s\n' "$before") <(printf '%s\n' "$after") >&2 || true
         return 1
     fi
+    if [[ ${#failed[@]} -gt 0 ]]; then
+        printf '\n%s of %s targets failed to build:\n' \
+            "${#failed[@]}" "${#COURSE_CHOSEN[@]}" >&2
+        printf '    %s\n' "${failed[@]}" >&2
+        return 1
+    fi
     if [[ "$COURSE_EXEC_FAILURES" -gt 0 ]]; then
         printf '\n%s of the programs did not exit cleanly (see above)\n' \
             "$COURSE_EXEC_FAILURES" >&2

scripts/course_targets.sh

@@ -98,7 +98,10 @@ _match_selection() {
 }
 
 _print_menu() {
-    printf '\n%s has %d targets:\n\n' "${COURSE_ROOT##*/}" "${#COURSE_TARGETS[@]}"
+    local plural="targets"
+    if [[ ${#COURSE_TARGETS[@]} -eq 1 ]]; then plural="target"; fi
+    printf '\n%s has %d %s:\n\n' \
+        "${COURSE_ROOT##*/}" "${#COURSE_TARGETS[@]}" "$plural"
     local i=1 t marker
     for t in "${COURSE_TARGETS[@]}"; do
         marker=""
@@ -116,7 +119,10 @@ _choose_target() {
     COURSE_CHOSEN=()
     local idx
 
-    if [[ ${#COURSE_TARGETS[@]} -eq 1 ]]; then
+    # A selection is validated even when there is only one target: silently
+    # running target 1 because you asked for target 5 is the same species of
+    # confusion as running something and not saying what.
+    if [[ ${#COURSE_TARGETS[@]} -eq 1 && -z "${COURSE_SELECT:-}" ]]; then
         COURSE_CHOSEN=("${COURSE_TARGETS[@]}")
         return 0
     fi