Update resolve.go to provide more human-friendly error output

CHANGELOG.md

@@ -25,7 +25,7 @@ A brief description of the categories of changes:
 [x.x.x]: https://github.com/bazelbuild/rules_python/releases/tag/x.x.x
 
 ### Changed
-* Nothing yet
+* (gazelle): Update error messages when unable to resolve a dependency to be more human-friendly.
 
 ### Added
 * Nothing yet

gazelle/python/resolve.go

@@ -206,11 +206,11 @@ func (py *Resolver) Resolve(
 								continue MODULES_LOOP
 							} else if cfg.ValidateImportStatements() {
 								err := fmt.Errorf(
-									"%[1]q at line %[2]d from %[3]q is an invalid dependency: possible solutions:\n"+
+									"%[1]q, line %[2]d: %[3]q is an invalid dependency: possible solutions:\n"+
 										"\t1. Add it as a dependency in the requirements.txt file.\n"+
-										"\t2. Instruct Gazelle to resolve to a known dependency using the gazelle:resolve directive.\n"+
-										"\t3. Ignore it with a comment '# gazelle:ignore %[1]s' in the Python file.\n",
-									moduleName, mod.LineNumber, mod.Filepath,
+										"\t2. Use the '# gazelle:resolve py %[3]s TARGET_LABEL' BUILD file directive to resolve to a known dependency.\n"+
+										"\t3. Ignore it with a comment '# gazelle:ignore %[3]s' in the Python file.\n",
+									mod.Filepath, mod.LineNumber, moduleName,
 								)
 								errs = append(errs, err)
 								continue POSSIBLE_MODULE_LOOP
@@ -236,9 +236,10 @@ func (py *Resolver) Resolve(
 							}
 							if len(sameRootMatches) != 1 {
 								err := fmt.Errorf(
-									"multiple targets (%s) may be imported with %q at line %d in %q "+
-										"- this must be fixed using the \"gazelle:resolve\" directive",
-									targetListFromResults(filteredMatches), moduleName, mod.LineNumber, mod.Filepath)
+									"%[1]q, line %[2]d: multiple targets (%[3]s) may be imported with %[4]q: possible solutions:\n"+
+										"\t1. Disambiguate the above multiple targets by removing duplicate srcs entries.\n"+
+										"\t2. Use the '# gazelle:resolve py %[4]s TARGET_LABEL' BUILD file directive to resolve to one of the above targets.\n",
+									mod.Filepath, mod.LineNumber, targetListFromResults(filteredMatches), moduleName)
 								errs = append(errs, err)
 								continue POSSIBLE_MODULE_LOOP
 							}
@@ -263,7 +264,7 @@ func (py *Resolver) Resolve(
 				for _, err := range errs {
 					joinedErrs = fmt.Sprintf("%s%s\n", joinedErrs, err)
 				}
-				log.Printf("ERROR: failed to validate dependencies for target %q: %v\n", from.String(), joinedErrs)
+				log.Printf("ERROR: failed to validate dependencies for target %q:\n\n%v", from.String(), joinedErrs)
 				hasFatalError = true
 			}
 		}

gazelle/python/testdata/invalid_imported_module/__init__.py

@@ -12,11 +12,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import foo.bar
+
 try:
     import grpc
 
     grpc_available = True
 except ImportError:
     grpc_available = False
 
-_ = grpc
+_ = bar(grpc)

gazelle/python/testdata/invalid_imported_module/foo/BUILD.in

@@ -0,0 +1,11 @@
+load("@rules_python//python:defs.bzl", "py_library")
+
+py_library(
+    name = "bar_1",
+    srcs = ["bar.py"],
+)
+
+py_library(
+    name = "bar_2",
+    srcs = ["bar.py"],
+)

gazelle/python/testdata/invalid_imported_module/test.yaml

@@ -16,7 +16,20 @@
 expect:
   exit_code: 1
   stderr: |
-    gazelle: ERROR: failed to validate dependencies for target "//:invalid_imported_module": "grpc" at line 16 from "__init__.py" is an invalid dependency: possible solutions:
+    gazelle: ERROR: failed to validate dependencies for target "//:invalid_imported_module":
+
+    "__init__.py", line 15: multiple targets (//foo:bar_1, //foo:bar_2) may be imported with "foo.bar": possible solutions:
+    	1. Disambiguate the above multiple targets by removing duplicate srcs entries.
+    	2. Use the '# gazelle:resolve py foo.bar TARGET_LABEL' BUILD file directive to resolve to one of the above targets.
+
+    "__init__.py", line 15: "foo" is an invalid dependency: possible solutions:
+    	1. Add it as a dependency in the requirements.txt file.
+    	2. Use the '# gazelle:resolve py foo TARGET_LABEL' BUILD file directive to resolve to a known dependency.
+    	3. Ignore it with a comment '# gazelle:ignore foo' in the Python file.
+
+    gazelle: ERROR: failed to validate dependencies for target "//:invalid_imported_module":
+
+    "__init__.py", line 18: "grpc" is an invalid dependency: possible solutions:
     	1. Add it as a dependency in the requirements.txt file.
-    	2. Instruct Gazelle to resolve to a known dependency using the gazelle:resolve directive.
+    	2. Use the '# gazelle:resolve py grpc TARGET_LABEL' BUILD file directive to resolve to a known dependency.
     	3. Ignore it with a comment '# gazelle:ignore grpc' in the Python file.