feat: distinguish uncacheable declared deps from unknown imports

src/layer_static_lint.jl

@@ -193,6 +193,18 @@ Salsa.@derived function derived_static_lint_diagnostics_for_root(rt, root)
     workspace_packages = lint_result.workspace_packages
     env = derived_environment(rt, project_uri)
 
+    # Names the project declares as dependencies. An unresolved import of one of
+    # these is a dependency whose symbols could not be indexed/cached (it would
+    # otherwise be in the env and resolve), as opposed to a name that simply
+    # isn't in the environment (typo / missing dependency).
+    project = derived_project(rt, project_uri)
+    declared_deps = project === nothing ? Set{String}() :
+        Set{String}(Iterators.flatten((
+            keys(project.regular_packages),
+            keys(project.stdlib_packages),
+            keys(project.deved_packages),
+        )))
+
     for uri in derived_include_closure(rt, root)
         current_res = get!(res, uri, Set{Diagnostic}())
 
@@ -209,12 +221,13 @@ Salsa.@derived function derived_static_lint_diagnostics_for_root(rt, root)
                 push!(current_res, Diagnostic(rng, :warning, "Missing reference: $(err[2].val)", nothing, Symbol[], "StaticLint.jl"))
             elseif StaticLint.haserror(err[2], meta_dict) && StaticLint.errorof(err[2], meta_dict) === StaticLint.UnresolvedImport
                 name = CSTParser.str_value(err[2])
-                msg = if StaticLint.is_in_wildcard_import(err[2])
-                    "Failed to resolve `$name`. Missing-reference checks are disabled in this scope and all nested scopes."
-                else
-                    "Failed to resolve `$name`. Anything imported through this statement is assumed to exist and will not be checked."
-                end
-                push!(current_res, Diagnostic(rng, :warning, msg, nothing, Symbol[], "StaticLint.jl"))
+                cause = name in declared_deps ?
+                    "`$name` is a declared dependency but its symbols could not be indexed." :
+                    "Failed to resolve `$name`."
+                consequence = StaticLint.is_in_wildcard_import(err[2]) ?
+                    "Missing-reference checks are disabled in this scope and all nested scopes." :
+                    "Anything imported through this statement is assumed to exist and will not be checked."
+                push!(current_res, Diagnostic(rng, :warning, "$cause $consequence", nothing, Symbol[], "StaticLint.jl"))
             elseif StaticLint.haserror(err[2], meta_dict) && StaticLint.errorof(err[2], meta_dict) isa StaticLint.LintCodes
                 code = StaticLint.errorof(err[2], meta_dict)
                 description = get(StaticLint.LintCodeDescriptions, code, "")

test/test_diagnostics.jl

@@ -1428,6 +1428,51 @@ end
     @test any(d -> startswith(d.message, "Failed to resolve `ActuallyUnresolved`"), diags)
 end
 
+@testitem "unresolved import: declared-but-uncacheable dep vs unknown name" begin
+    using JuliaWorkspaces.URIs2: URI
+
+    # `DeclaredButUncached` is listed in the manifest (so it's a declared
+    # dependency) but no symbols are cached for it, so it never enters the env.
+    # `TotallyUnknownPkg` is not declared anywhere.
+    project_toml = """
+    name = "UncachedDep"
+    uuid = "aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeee41"
+    version = "0.1.0"
+
+    [deps]
+    DeclaredButUncached = "12345678-1234-1234-1234-123456789abc"
+    """
+    manifest_toml = """
+    julia_version = "1.11.0"
+    manifest_format = "2.0"
+    project_hash = "abc123"
+
+    [[deps.DeclaredButUncached]]
+    git-tree-sha1 = "0000000000000000000000000000000000000000"
+    uuid = "12345678-1234-1234-1234-123456789abc"
+    version = "1.0.0"
+    """
+    source = """
+    module UncachedDep
+    import DeclaredButUncached: foo
+    using TotallyUnknownPkg
+    end
+    """
+
+    jw = JuliaWorkspace()
+    add_file!(jw, TextFile(URI("file:///uncacheddep/Project.toml"), SourceText(project_toml, "toml")))
+    add_file!(jw, TextFile(URI("file:///uncacheddep/Manifest.toml"), SourceText(manifest_toml, "toml")))
+    add_file!(jw, TextFile(URI("file:///uncacheddep/src/UncachedDep.jl"), SourceText(source, "julia")))
+    JuliaWorkspaces.set_input_env_ready!(jw.runtime, true)
+
+    diags = get_diagnostic(jw, URI("file:///uncacheddep/src/UncachedDep.jl"))
+
+    # Declared dependency: message attributes the failure to indexing/caching
+    @test any(d -> d.message == "`DeclaredButUncached` is a declared dependency but its symbols could not be indexed. Anything imported through this statement is assumed to exist and will not be checked.", diags)
+    # Undeclared name: keeps the generic "Failed to resolve" wording
+    @test any(d -> d.message == "Failed to resolve `TotallyUnknownPkg`. Missing-reference checks are disabled in this scope and all nested scopes.", diags)
+end
+
 @testitem "missing-refs: default is all (getfield refs checked)" begin
     using JuliaWorkspaces.URIs2: URI