Exceptions: Raising code uses proper constructers now

src/fsh.nim

@@ -25,6 +25,41 @@ let builtins: array[4, string] = [
 "exit",
 ]
 
+# Exception types
+type
+  ShellError= object of CatchableError
+    line: int
+    col: int
+    whileExec: string
+  ShellVariableError= object of ShellError
+    variable: string
+  ShellCommandError = object of ShellError
+    command: string
+
+# procs for making procedures
+proc newShellException(msg: string, line=0, col=0, whileExec=""): ref ShellError =
+  var e = newException(ShellError, msg)
+  e.line=line
+  e.col=col
+  e.whileExec = whileExec
+  return e
+
+proc newShellVariableException(msg: string, vari: string, line=0, col=0, whileExec=""): ref ShellVariableError =
+  var e= newException(ShellVariableError, vari & ": " & msg)
+  e.variable =vari
+  e.line=line
+  e.col=col
+  e.whileExec=whileExec
+  return e
+
+proc newShellCommandException(msg: string, command: string, line=0, col=0, whileExec=""): ref ShellCommandError =
+  var e=newException(ShellCommandError, command & ": " & msg)
+  e.command=command
+  e.line=line
+  e.col=col
+  e.whileExec=whileExec
+  return e
+
 # forward declarations
 proc eval(cmd: string): string
 proc substitute(strm: Stream, delim = ";\p"): string
@@ -150,7 +185,8 @@ proc evalVariable(vari: string): string =
     result=shellVariables[vari]
   elif envVariables.hasKey(vari):
     result = envVariables[vari]
-  else: raise newException(Exception, "No such variable: " & vari & ".")
+  else:
+    raise newShellVariableException("No such variable", vari)
 
 # substitute does a substitution on the stream passed in
 proc substitute(strm: Stream, delim=";\p"): string =
@@ -205,17 +241,17 @@ proc runBuiltin(builtin: string, args: openArray[string]): string =
   case builtin:
     of "set":
       if args.len < 2:
-        raise newException(Exception, "Set: not enough arguments provided")
+        raise newShellCommandException("Not enough arguments provided", "set")
       shellVariables[args[0]] = args[1..^1].join(" ")
       return ""
     of "setenv":
       if args.len < 2:
-        raise newException(Exception, "setenv: Not enough arguments provided")
+        raise newShellCommandException("Not enough arguments provided", "setenv")
       try:
         envVariables[args[0]] = args[1..^1].join(":")
         putEnv(args[0], args[1..^1].join(":"))
       except OSError as e:
-        raise newException(Exception, "setenv: " & e.msg)
+        raise newShellCommandException(e.msg, "setenv")
       return ""
     of "echo":
       if args[0] == "-n":
@@ -241,7 +277,7 @@ proc runBuiltin(builtin: string, args: openArray[string]): string =
           stdout.write(args.join(" "), "\p")
           quit(0)
     else:
-      raise newException(Exception, "Fsh: No such builtin implemented")
+      raise newShellCommandException("No such builtin implemented", builtin)
 
 # executes executes the command. For now it involves catting the command and printing it
 proc execute(cmd: string): int =
@@ -256,9 +292,12 @@ proc execute(cmd: string): int =
       stdout.write(runBuiltin(progname, args))
       result = 0
       continue
-    let ps = startProcess(progname, args=args, options={poUsePath, poParentStreams})
-    result =  ps.waitForExit
-    ps.close
+    try:
+      let ps = startProcess(progname, args=args, options={poUsePath, poParentStreams})
+      result =  ps.waitForExit
+      ps.close
+    except OSError as e:
+      raise newShellCommandException("No such command", progname)
   strm.close
 
 # eval evaluates the given string
@@ -273,9 +312,12 @@ proc eval(cmd: string): string =
     if progname in builtins:
       result = runBuiltin(progname, args)
       continue
-    let ps = startProcess(progname, args=args, options={poUsePath})
-    result=ps.outputStream.readAll
-    ps.close
+    try:
+      let ps = startProcess(progname, args=args, options={poUsePath})
+      result=ps.outputStream.readAll
+      ps.close
+    except OSError as e:
+      raise newShellCommandException("No such command", progname)
   strm.close
 
 when isMainModule: