[shared-ini-file-loader] loadSharedConfigFiles is broken on empty value - regression since v2.0.13

[xfournet]

Describe the bug

The utility loadSharedConfigFiles incorrecly prefix keys when previous key has an empty value.
In the example below, in latest version, the region key is incorrectly prefixed with cli_pager.

Steps to reproduce

// test.mjs
import { tmpdir } from "os";
import { mkdtemp, rm, writeFile } from "fs/promises";
import { loadSharedConfigFiles } from "@smithy/shared-ini-file-loader";

const tempDir = await mkdtemp(tmpdir());

const filepath = `${tempDir}/credentials`;
await writeFile(filepath, ``);

const configFilepath = `${tempDir}/config`;
await writeFile(
  configFilepath,
  `[profile dev]
cli_pager=  
region = us-east-2`
);

const sharedConfigFiles = await loadSharedConfigFiles({
  filepath,
  configFilepath,
});

console.log(JSON.stringify(sharedConfigFiles, null, 2));

await rm(tempDir, { recursive: true });

Observed behavior

v2.0.12 ✅ correct behavior

{
  "configFile": {
    "dev": {
      "region": "us-east-2"
    }
  },
  "credentialsFile": {}
}

v2.0.13 ❌ incorrect behavior

{
  "configFile": {},
  "credentialsFile": {}
}

v2.1.0 and v2.2.0 ❌ incorrect behavior

{
  "configFile": {
    "dev": {
      "cli_pager.region": "us-east-2"
    }
  },
  "credentialsFile": {}
}

Additional context

The regression comes from 60e88af (#986) and then from aa86b3f (#989)

[trivikr]

As per the SDK reference for file-format, the subsections appears after the main section. And that's how the JS SDK v3 currently reads the configuration.

A workaround will be to move region above subsection as follows:

[profile dev]
region = us-east-2
cli_pager=  

In the meantime, I'll investigate if we can read values after subsections.

[xfournet]

@trivikr yes the documentation specify that subsettings should have one or many spaces before. That is workly perfectly with AWS CLI and JS SDK until v2.0.12

I'm rather waiting for a new release instead of using the workaround : it may be costly to identify all the files to be updated, and in some situation I may not have the required permission to update them promptly.