[internal] index file should be invalidate when input file is newer

[cderv]

If the input file is newer that the index file stored, then we should consider it outdated

this way is will be rewritten with newer content. cc @dragonstyle as we discussed

Context

Found while looking at #8016

The index file is read from local storage as a cache, but I notice that a complete unrelated version of my index.qmd was internally loaded while debugging. This is because we were finding the .qmd was newer but re-reading the existing (wrong) index file which leads the futher processing below to use an unrelated content to my real index.qmd

quarto-cli/src/project/project-index.ts

Lines 136 to 143 in bac63d8

	// check if we have an index that's still current vis-a-vis the
	// last modified date of the source file
	const index = readInputTargetIndexIfStillCurrent(projectDir, input);
	if (!index) {
	return {
	missingReason: "stale",
	};
	}

quarto-cli/src/project/project-config.ts

Lines 97 to 115 in bac63d8

	export async function partitionedMarkdownForInput(
	projectDir: string,
	input: string,
	) {
	// first see if we can get the partioned markdown out of the index
	const { index } = readInputTargetIndex(projectDir, input);
	if (index) {
	return index.markdown;
	// otherwise fall back to calling the engine to do the partition
	} else {
	const inputPath = join(projectDir, input);
	const engine = fileExecutionEngine(inputPath);
	if (engine) {
	return await engine.partitionedMarkdown(inputPath);
	} else {
	return undefined;
	}
	}
	}

This PR makes sure we return undefined to make clear that no index file is found because stale. it will then be rewritten.

This is there since several month, I am surprised we were not bitten by that, but I am pretty sure something is not right. I believe this is fixed is the right one but unsure.

The new logic since performance fix (#5245) is more complex than the previous one which was

quarto-cli/src/project/project-index.ts

Lines 182 to 198 in 9f61990

	function readInputTargetIndexIfStillCurrent(projectDir: string, input: string) {
	const inputFile = join(projectDir, input);
	const indexFile = inputTargetIndexFile(projectDir, input);
	if (existsSync(indexFile)) {
	const inputMod = Deno.statSync(inputFile).mtime;
	const indexMod = Deno.statSync(indexFile).mtime;
	if (
	inputMod && indexMod && (indexMod >= inputMod)
	) {
	try {
	return JSON.parse(Deno.readTextFileSync(indexFile)) as InputTargetIndex;
	} catch {
	return undefined;
	}
	}
	}
	}

So hopefully I got it right

[dragonstyle]

FWIW this looks correct to me.

[cscheid]

Nice catch! LGTM as well.