Function resolvePathFromImportMap

Example

import { assertEquals, assertThrows } from "jsr:@std/assert"

// aliasing our function for brevity
const fn = resolvePathFromImportMap

const my_import_map = {
	// non-directory specifiers (i.e. not used for prefixing)
	"square"                     : "./module/shapes/square.js",
	"circle"                     : "https://example.com/shapes/circle.js",
	"http://shape.com/square.js" : "https://example.com/shapes/square.js",
	"./shapes/circle"            : "/modules/shapes/circle/",

	// directory specifiers (i.e. used for matching prefixing of path alias)
	"shapes/"                    : "./module/shapes/",
	"other-shapes/"              : "https://example.com/modules/shapes/",
	"other-shapes/triangle/"     : "file:///C:/Users/illuminati/",
	"../modules/shapes/"         : "/modules/shapes/",

	// incorrect import map value.
	// resolving this key will throw an error because the value should end in a trailing slash,
	// since the key also ends in a trailing slash.
	"modules/css/"               : "/modules/shapes/css",
}

assertEquals(
	fn("square", my_import_map),
	"./module/shapes/square.js",
)

assertEquals(
	fn("circle", my_import_map),
	"https://example.com/shapes/circle.js",
)

// the following is not resolved because the `"circle"` key in `my_import_map` does not end with a trailing slash,
// which is a requirement for matching prefix directories.
assertEquals(
	fn("circle/bold-circle.js", my_import_map),
	undefined,
)

assertEquals(
	fn("http://shape.com/square.js", my_import_map),
	"https://example.com/shapes/square.js",
)

// even though there is no exact match of the non-normalized input path here,
// once it is normalized inside of the function, it matches the same key as the previous test's.
assertEquals(
	fn("http://shape.com/lib/../square.js", my_import_map),
	"https://example.com/shapes/square.js",
)

// even relative imports can be thought as path aliases, so long as there is a key for it in `my_import_map`.
// moreover, it is permissible for an import-map value to end with a trailing slash, even when its associated key does not.
assertEquals(
	fn("./shapes/circle", my_import_map),
	"/modules/shapes/circle/",
)

assertEquals(
	fn("shapes/", my_import_map),
	"./module/shapes/",
)

assertEquals(
	fn("shapes/rectangle.ts", my_import_map),
	"./module/shapes/rectangle.ts",
)

assertEquals(
	fn("other-shapes", my_import_map),
	undefined,
)

assertEquals(
	fn("other-shapes/doritos.html", my_import_map),
	"https://example.com/modules/shapes/doritos.html",
)

// the path alias is matched with the longest key first,
// which is why it resolves to a path different from the prior test's key.
assertEquals(
	fn("other-shapes/triangle/doritos.html", my_import_map),
	"file:///C:/Users/illuminati/doritos.html",
)

// the value of the key "modules/css/" is invalid (non-specs compliant),
// since it does not end with a trailing slash, whereas the key does end with one.
assertThrows(() => {
	fn("modules/css/cicle.css", my_import_map)
})
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