Allow for expressions in pxt.json:fileDependencies

docs/extensions/pxt-json.md

@@ -152,6 +152,11 @@ the entire extension in the editor.
 There is no point in adding them as regular `dependencies` - that would negate the
 effects of `fileDependencies` and always include both the dependencies and files.
 
+The `fileDependencies` allows expressions with `!`, `&&` and `||` (with the usual priorities).
+Parenthesis are not supported.
+
+In addition to packages, one can also say something like `target:microbit` or `target:arcade`.
+
 In future, we may allow things like `"radio >= 1.2.3"`, but for now the package identifier is
 the only thing supported.
 

pxtlib/package.ts

@@ -730,24 +730,40 @@ namespace pxt {
             else
                 res = this.config.files.slice(0);
             const fd = this.config.fileDependencies
-            if (this.config.fileDependencies)
+            if (fd) {
                 res = res.filter(fn => {
-                    let cond = U.lookup(fd, fn)
-                    if (!cond) return true
-                    cond = cond.trim()
-                    if (!cond) return true
-                    if (/^[\w-]+$/.test(cond)) {
-                        const dep = this.parent.resolveDep(cond)
-                        if (dep && !dep.cppOnly)
-                            return true
+                    const checkCond = (cond: string): boolean => {
+                        if (!cond) return true
+                        cond = cond.trim()
+                        if (!cond) return true
+                        if (cond[0] == "!")
+                            return !checkCond(cond.slice(1))
+                        const spl = cond.split(":")
+                        if (spl.length == 2) {
+                            switch (spl[0]) {
+                                case "target":
+                                    return spl[1] == pxt.appTarget.id
+                                default:
+                                    break
+                            }
+                        } else if (/^[\w-]+$/.test(cond)) {
+                            const dep = this.parent.resolveDep(cond)
+                            if (dep && !dep.cppOnly)
+                                return true
+                            return false
+                        }
+                        if (!Package.depWarnings[cond]) {
+                            Package.depWarnings[cond] = true
+                            pxt.log(`invalid dependency expression: ${cond} in ${this.id}/${fn}`)
+                        }
                         return false
                     }
-                    if (!Package.depWarnings[cond]) {
-                        Package.depWarnings[cond] = true
-                        pxt.log(`invalid dependency expression: ${cond} in ${this.id}/${fn}`)
-                    }
-                    return false
+
+                    const cond = U.lookup(fd, fn)
+                    const dysj = cond.split("||")
+                    return dysj.some(d => d.split("&&").every(checkCond))
                 })
+            }
             return res
         }