test(lint-once): match RUN case-insensitively, follow buildx builds

WIP round 9: items 1-3. Verification matrix still to re-run.

test/packaging/lint-once.test.ts

@@ -317,6 +317,21 @@ const scripts = packageScripts();
 // the rest of the file, for the same reason every other dead end here is.
 const HEREDOC_OPEN = /<<-?\s*(['"]?)([A-Za-z_][A-Za-z0-9_]*)\1/;
 
+// Dockerfile instruction keywords are case-insensitive and are separated from
+// their arguments by any run of whitespace, so `run yarn run prettier ...` and
+// a tab-separated `RUN\tyarn run prettier ...` are both instructions the image
+// really executes. A literal `line.startsWith("RUN ")` saw neither, and either
+// one appended to the Dockerfile put a second prettier pass into the image
+// that `script/cibuild` builds while this file still reported green. The
+// separator is consumed by the match rather than by a fixed-width `slice`, so
+// the captured command is the same string for a space and for a tab, and the
+// heredoc terminator is read off that command exactly as before.
+//
+// Leading whitespace before the keyword — which a Dockerfile also permits — is
+// already gone by this point: `joinContinuations` trims every line, so an
+// indented instruction arrives here flush and needs nothing further.
+const DOCKER_RUN = /^RUN\s+(.*)$/i;
+
 const dockerRunCommands = (text: string): string[] => {
     const commands: string[] = [];
     let terminator: string | null = null;
@@ -326,8 +341,9 @@ const dockerRunCommands = (text: string): string[] => {
             else commands.push(line);
             continue;
         }
-        if (!line.startsWith("RUN ")) continue;
+        const run = DOCKER_RUN.exec(line);
-        const command = line.slice("RUN ".length);
+        if (run === null) continue;
+        const command = run[1] as string;
         terminator = HEREDOC_OPEN.exec(command)?.[2] ?? null;
         commands.push(command);
     }
@@ -346,8 +362,10 @@ const resolve = (node: string): string[] => {
     }
     // The `run:` steps of a workflow, in file order. `uses:` steps are actions,
     // not commands, and have no edges into this repo's graph. A `run: |` block
-    // would resolve to the bare `|`, which reaches nothing and therefore fails
+    // resolves to the bare `|`, which reaches nothing — so the count is exactly
-    // the count rather than passing quietly.
+    // what such a step does NOT move, and it is the pinned resolved list, not
+    // the count, that turns it red. See the exact-equality test at the bottom
+    // of this file.
     if (node.startsWith("workflow:")) {
         return executable(read(node.slice("workflow:".length)))
             .filter((line) => /^-?\s*run:\s*\S/.test(line))
@@ -390,6 +408,28 @@ const commandsOf = (node: string): string[] => {
     return commands;
 };
 
+// Which invocation shapes read as a build, and which do not.
+//
+// RECOGNISED: `docker build`, `docker buildx build`, and either of those
+// reached through global flags between the command and the subcommand —
+// `docker --context ci build`, `docker -H tcp://host:2375 build`,
+// `docker --debug buildx build`. A global flag's separate argument is stepped
+// over (`--context ci`), and an `=`-joined one is a single token
+// (`--context=ci`). `docker buildx build` was the concrete miss: `\bdocker\s+
+// build\b` cannot reach across `buildx`, so `docker buildx build -f
+// Dockerfile.extra .` in script/cibuild emitted no edge at all — not even the
+// default `Dockerfile` one — and a tree running prettier twice reported green.
+//
+// NOT RECOGNISED, deliberately: `docker compose build`, which builds compose
+// services out of a compose file this parser does not read, so resolving it
+// against a Dockerfile path would be a wrong answer rather than a missing one;
+// `docker builder build`; and any spelling that puts a non-flag word other
+// than `buildx` between `docker` and `build`. Only `-`-prefixed tokens (plus
+// their arguments) and the single literal `buildx` are stepped over, so
+// `docker run -f build` and `docker image build`-style shapes do not match.
+const DOCKER_BUILD =
+    /\bdocker(?:\s+-{1,2}[A-Za-z][\w-]*(?:=\S+)?(?:\s+[^-\s]\S*)?)*(?:\s+buildx)?\s+build\b/g;
+
 const edgesOf = (line: string): string[] => {
     const edges: string[] = [];
 
@@ -469,7 +509,7 @@ const edgesOf = (line: string): string[] => {
     // separators and nothing more: a separator inside quotes or a `$(...)`
     // substitution ends the slice anyway, and a newline-separated command list
     // is already one line per invocation by the time it gets here.
-    for (const match of line.matchAll(/\bdocker\s+build\b/g)) {
+    for (const match of line.matchAll(DOCKER_BUILD)) {
         const invocation = line
             .slice(match.index)
             .split(/&&|\|\||;|\|/)[0] as string;