fix: allow "src" and "bin" module mappings to win over "runfiles"

This fixes an issue in the Angular repo where the duplicate `runfiles` mappings:

```
["runfiles", "angular/packages/compiler"] and ["bin", "angular/packages/compiler"]
```

sneaks through this nodejs_binaries:

```
nodejs_binary(
name = "ngc_bin",
data = [
"//packages/compiler-cli",
"@npm//chokidar",
"@npm//reflect-metadata",
],
entry_point = "//packages/compiler-cli:src/main.ts",
)

nodejs_binary(
name = "ng_xi18n",
data = [
"//packages/compiler-cli",
"@npm//chokidar",
"@npm//reflect-metadata",
],
entry_point = "//packages/compiler-cli:src/extract_i18n.ts",
)
```

which depends on `//packages/compiler-cli` which depends on `//packages/compiler`. So when building the ng_test target:

```
nodejs_test(
name = "integrationtest",
data = [
":ngc_bin",
":ng_xi18n",
"@nodejs//:node",
"@npm//domino",
"@npm//chokidar",
"@npm//source-map-support",
"@npm//shelljs",
"@npm//typescript",
"@npm//reflect-metadata",
"@npm//rxjs",
"@npm//tslib",
"@npm//jasmine/bin:jasmine",
"@npm//xhr2",
"@npm//@types/node",
"@npm//@types/jasmine",
# we need to reference zone.d.ts typing file from zone.js build target
# instead of npm because angular repo will not depends on npm zone.js
# any longer.
"//packages/zone.js/lib:zone_d_ts",
# we need to reference zone.js npm_package build target
# instead of npm because angular repo will not depends on npm zone.js
# any longer, so we need to build a zone.js npm release first.
"//packages/zone.js:npm_package",
"//packages/animations:npm_package",
"//packages/common:npm_package",
"//packages/compiler:npm_package",
"//packages/compiler-cli:npm_package",
"//packages/core:npm_package",
"//packages/forms:npm_package",
"//packages/http:npm_package",
"//packages/platform-browser:npm_package",
"//packages/platform-browser-dynamic:npm_package",
"//packages/platform-server:npm_package",
"//packages/router:npm_package",
] + glob(["**/*"]),
entry_point = "test.js",
tags = ["no-ivy-aot"],
)
```

it has both mappings causing the linker to error out with conflicting module mappings `["runfiles", "angular/packages/compiler"] and ["bin", "angular/packages/compiler"]`.

Fix is to just allow this and allow both "src" and "bin" to win a conflicting over "runfiles" mapping.

Author: gregmagolan

internal/linker/link_node_modules.bzl

@@ -34,6 +34,21 @@ def add_arg(args, arg):
     else:
         args.add(arg)
 
+def _link_mapping(label, mappings, k, v):
+    if k in mappings and mappings[k] != v:
+        if v[1] == mappings[k][1]:
+            # Allow "src" and "bin" to win over "runfiles"
+            # For example,
+            #    mappings[k] = ["runfiles", "angular/packages/compiler"]
+            #    v           = ["bin", "angular/packages/compiler"]
+            if mappings[k][0] == "runfiles":
+                return True
+            elif v[0] != "runfiles":
+                return False
+        fail(("conflicting mapping at %s: %s maps to both %s and %s" % (label, k, mappings[k], v)), "deps")
+    else:
+        return True
+
 def write_node_modules_manifest(ctx, extra_data = []):
     """Writes a manifest file read by the linker, containing info about resolving runtime dependencies
 
@@ -62,11 +77,9 @@ def write_node_modules_manifest(ctx, extra_data = []):
 
         # ...first-party packages to be linked into the node_modules tree
         for k, v in getattr(dep, _ASPECT_RESULT_NAME, {}).items():
-            if k in mappings and mappings[k] != v:
-                fail(("conflicting module mapping at %s: %s maps to both %s and %s" %
-                      (dep.label, k, mappings[k], v)), "deps")
-            _debug(ctx.var, "Linking %s: %s" % (k, v))
-            mappings[k] = v
+            if _link_mapping(dep.label, mappings, k, v):
+                _debug(ctx.var, "Linking %s: %s" % (k, v))
+                mappings[k] = v
 
     # Write the result to a file, and use the magic node option --bazel_node_modules_manifest
     # The launcher.sh will peel off this argument and pass it to the linker rather than the program.
@@ -102,11 +115,6 @@ def get_module_mappings(label, attrs, vars, rule_kind, srcs = [], workspace_name
     for name in _MODULE_MAPPINGS_DEPS_NAMES:
         for dep in getattr(attrs, name, []):
             for k, v in getattr(dep, _ASPECT_RESULT_NAME, {}).items():
-                if k in mappings and mappings[k] != v:
-                    fail(("duplicate module mapping at %s: %s maps to both %s and %s" %
-                          (label, k, mappings[k], v)), "deps")
-                _debug(vars, "target %s propagating module mapping %s: %s" % (dep, k, v))
-
                 # A package which was reachable transitively via a *_binary or *_test
                 # rule is assumed to be in the runfiles of that binary,
                 # so we switch the linker target root.
@@ -115,9 +123,10 @@ def get_module_mappings(label, attrs, vars, rule_kind, srcs = [], workspace_name
                 # but it seems that this info is only available in Bazel Java internals.
                 # TODO: revisit whether this is the correct condition after downstream testing
                 if rule_kind.endswith("_binary") or rule_kind.endswith("_test"):
-                    mappings[k] = ["runfiles", v[1]]
-                else:
+                    v = ["runfiles", v[1]]
+                if _link_mapping(label, mappings, k, v):
                     mappings[k] = v
+                    _debug(vars, "target %s propagating module mapping %s: %s" % (dep, k, v))
 
     if not getattr(attrs, "module_name", None) and not getattr(attrs, "module_root", None):
         # No mappings contributed here, short-circuit with the transitive ones we collected
@@ -141,12 +150,10 @@ def get_module_mappings(label, attrs, vars, rule_kind, srcs = [], workspace_name
     else:
         mr = ["bin", mr]
 
-    if mn in mappings and mappings[mn] != mr:
-        fail(("duplicate module mapping at %s: %s maps to both %s and %s" %
-              (label, mn, mappings[mn], mr)), "deps")
-    _debug(vars, "target %s adding module mapping %s: %s" % (label, mn, mr))
+    if _link_mapping(label, mappings, mn, mr):
+        _debug(vars, "target %s adding module mapping %s: %s" % (label, mn, mr))
+        mappings[mn] = mr
 
-    mappings[mn] = mr
     return mappings
 
 # When building a mapping for use at runtime, we need paths to be relative to